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|
- # -*- coding: utf-8 -*-
- # Autogenerated by Sphinx on Tue Feb 4 15:37:58 2025
- # as part of the release process.
- topics = {'assert': 'The "assert" statement\n'
- '**********************\n'
- '\n'
- 'Assert statements are a convenient way to insert debugging '
- 'assertions\n'
- 'into a program:\n'
- '\n'
- ' assert_stmt ::= "assert" expression ["," expression]\n'
- '\n'
- 'The simple form, "assert expression", is equivalent to\n'
- '\n'
- ' if __debug__:\n'
- ' if not expression: raise AssertionError\n'
- '\n'
- 'The extended form, "assert expression1, expression2", is '
- 'equivalent to\n'
- '\n'
- ' if __debug__:\n'
- ' if not expression1: raise AssertionError(expression2)\n'
- '\n'
- 'These equivalences assume that "__debug__" and "AssertionError" '
- 'refer\n'
- 'to the built-in variables with those names. In the current\n'
- 'implementation, the built-in variable "__debug__" is "True" under\n'
- 'normal circumstances, "False" when optimization is requested '
- '(command\n'
- 'line option "-O"). The current code generator emits no code for '
- 'an\n'
- '"assert" statement when optimization is requested at compile '
- 'time.\n'
- 'Note that it is unnecessary to include the source code for the\n'
- 'expression that failed in the error message; it will be displayed '
- 'as\n'
- 'part of the stack trace.\n'
- '\n'
- 'Assignments to "__debug__" are illegal. The value for the '
- 'built-in\n'
- 'variable is determined when the interpreter starts.\n',
- 'assignment': 'Assignment statements\n'
- '*********************\n'
- '\n'
- 'Assignment statements are used to (re)bind names to values and '
- 'to\n'
- 'modify attributes or items of mutable objects:\n'
- '\n'
- ' assignment_stmt ::= (target_list "=")+ (starred_expression '
- '| yield_expression)\n'
- ' target_list ::= target ("," target)* [","]\n'
- ' target ::= identifier\n'
- ' | "(" [target_list] ")"\n'
- ' | "[" [target_list] "]"\n'
- ' | attributeref\n'
- ' | subscription\n'
- ' | slicing\n'
- ' | "*" target\n'
- '\n'
- '(See section Primaries for the syntax definitions for '
- '*attributeref*,\n'
- '*subscription*, and *slicing*.)\n'
- '\n'
- 'An assignment statement evaluates the expression list '
- '(remember that\n'
- 'this can be a single expression or a comma-separated list, the '
- 'latter\n'
- 'yielding a tuple) and assigns the single resulting object to '
- 'each of\n'
- 'the target lists, from left to right.\n'
- '\n'
- 'Assignment is defined recursively depending on the form of the '
- 'target\n'
- '(list). When a target is part of a mutable object (an '
- 'attribute\n'
- 'reference, subscription or slicing), the mutable object must\n'
- 'ultimately perform the assignment and decide about its '
- 'validity, and\n'
- 'may raise an exception if the assignment is unacceptable. The '
- 'rules\n'
- 'observed by various types and the exceptions raised are given '
- 'with the\n'
- 'definition of the object types (see section The standard type\n'
- 'hierarchy).\n'
- '\n'
- 'Assignment of an object to a target list, optionally enclosed '
- 'in\n'
- 'parentheses or square brackets, is recursively defined as '
- 'follows.\n'
- '\n'
- '* If the target list is a single target with no trailing '
- 'comma,\n'
- ' optionally in parentheses, the object is assigned to that '
- 'target.\n'
- '\n'
- '* Else:\n'
- '\n'
- ' * If the target list contains one target prefixed with an '
- 'asterisk,\n'
- ' called a “starred” target: The object must be an iterable '
- 'with at\n'
- ' least as many items as there are targets in the target '
- 'list, minus\n'
- ' one. The first items of the iterable are assigned, from '
- 'left to\n'
- ' right, to the targets before the starred target. The '
- 'final items\n'
- ' of the iterable are assigned to the targets after the '
- 'starred\n'
- ' target. A list of the remaining items in the iterable is '
- 'then\n'
- ' assigned to the starred target (the list can be empty).\n'
- '\n'
- ' * Else: The object must be an iterable with the same number '
- 'of items\n'
- ' as there are targets in the target list, and the items '
- 'are\n'
- ' assigned, from left to right, to the corresponding '
- 'targets.\n'
- '\n'
- 'Assignment of an object to a single target is recursively '
- 'defined as\n'
- 'follows.\n'
- '\n'
- '* If the target is an identifier (name):\n'
- '\n'
- ' * If the name does not occur in a "global" or "nonlocal" '
- 'statement\n'
- ' in the current code block: the name is bound to the object '
- 'in the\n'
- ' current local namespace.\n'
- '\n'
- ' * Otherwise: the name is bound to the object in the global '
- 'namespace\n'
- ' or the outer namespace determined by "nonlocal", '
- 'respectively.\n'
- '\n'
- ' The name is rebound if it was already bound. This may cause '
- 'the\n'
- ' reference count for the object previously bound to the name '
- 'to reach\n'
- ' zero, causing the object to be deallocated and its '
- 'destructor (if it\n'
- ' has one) to be called.\n'
- '\n'
- '* If the target is an attribute reference: The primary '
- 'expression in\n'
- ' the reference is evaluated. It should yield an object with\n'
- ' assignable attributes; if this is not the case, "TypeError" '
- 'is\n'
- ' raised. That object is then asked to assign the assigned '
- 'object to\n'
- ' the given attribute; if it cannot perform the assignment, it '
- 'raises\n'
- ' an exception (usually but not necessarily '
- '"AttributeError").\n'
- '\n'
- ' Note: If the object is a class instance and the attribute '
- 'reference\n'
- ' occurs on both sides of the assignment operator, the '
- 'right-hand side\n'
- ' expression, "a.x" can access either an instance attribute or '
- '(if no\n'
- ' instance attribute exists) a class attribute. The left-hand '
- 'side\n'
- ' target "a.x" is always set as an instance attribute, '
- 'creating it if\n'
- ' necessary. Thus, the two occurrences of "a.x" do not '
- 'necessarily\n'
- ' refer to the same attribute: if the right-hand side '
- 'expression\n'
- ' refers to a class attribute, the left-hand side creates a '
- 'new\n'
- ' instance attribute as the target of the assignment:\n'
- '\n'
- ' class Cls:\n'
- ' x = 3 # class variable\n'
- ' inst = Cls()\n'
- ' inst.x = inst.x + 1 # writes inst.x as 4 leaving Cls.x '
- 'as 3\n'
- '\n'
- ' This description does not necessarily apply to descriptor\n'
- ' attributes, such as properties created with "property()".\n'
- '\n'
- '* If the target is a subscription: The primary expression in '
- 'the\n'
- ' reference is evaluated. It should yield either a mutable '
- 'sequence\n'
- ' object (such as a list) or a mapping object (such as a '
- 'dictionary).\n'
- ' Next, the subscript expression is evaluated.\n'
- '\n'
- ' If the primary is a mutable sequence object (such as a '
- 'list), the\n'
- ' subscript must yield an integer. If it is negative, the '
- 'sequence’s\n'
- ' length is added to it. The resulting value must be a '
- 'nonnegative\n'
- ' integer less than the sequence’s length, and the sequence is '
- 'asked\n'
- ' to assign the assigned object to its item with that index. '
- 'If the\n'
- ' index is out of range, "IndexError" is raised (assignment to '
- 'a\n'
- ' subscripted sequence cannot add new items to a list).\n'
- '\n'
- ' If the primary is a mapping object (such as a dictionary), '
- 'the\n'
- ' subscript must have a type compatible with the mapping’s key '
- 'type,\n'
- ' and the mapping is then asked to create a key/value pair '
- 'which maps\n'
- ' the subscript to the assigned object. This can either '
- 'replace an\n'
- ' existing key/value pair with the same key value, or insert a '
- 'new\n'
- ' key/value pair (if no key with the same value existed).\n'
- '\n'
- ' For user-defined objects, the "__setitem__()" method is '
- 'called with\n'
- ' appropriate arguments.\n'
- '\n'
- '* If the target is a slicing: The primary expression in the '
- 'reference\n'
- ' is evaluated. It should yield a mutable sequence object '
- '(such as a\n'
- ' list). The assigned object should be a sequence object of '
- 'the same\n'
- ' type. Next, the lower and upper bound expressions are '
- 'evaluated,\n'
- ' insofar they are present; defaults are zero and the '
- 'sequence’s\n'
- ' length. The bounds should evaluate to integers. If either '
- 'bound is\n'
- ' negative, the sequence’s length is added to it. The '
- 'resulting\n'
- ' bounds are clipped to lie between zero and the sequence’s '
- 'length,\n'
- ' inclusive. Finally, the sequence object is asked to replace '
- 'the\n'
- ' slice with the items of the assigned sequence. The length '
- 'of the\n'
- ' slice may be different from the length of the assigned '
- 'sequence,\n'
- ' thus changing the length of the target sequence, if the '
- 'target\n'
- ' sequence allows it.\n'
- '\n'
- '**CPython implementation detail:** In the current '
- 'implementation, the\n'
- 'syntax for targets is taken to be the same as for expressions, '
- 'and\n'
- 'invalid syntax is rejected during the code generation phase, '
- 'causing\n'
- 'less detailed error messages.\n'
- '\n'
- 'Although the definition of assignment implies that overlaps '
- 'between\n'
- 'the left-hand side and the right-hand side are ‘simultaneous’ '
- '(for\n'
- 'example "a, b = b, a" swaps two variables), overlaps *within* '
- 'the\n'
- 'collection of assigned-to variables occur left-to-right, '
- 'sometimes\n'
- 'resulting in confusion. For instance, the following program '
- 'prints\n'
- '"[0, 2]":\n'
- '\n'
- ' x = [0, 1]\n'
- ' i = 0\n'
- ' i, x[i] = 1, 2 # i is updated, then x[i] is '
- 'updated\n'
- ' print(x)\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 3132** - Extended Iterable Unpacking\n'
- ' The specification for the "*target" feature.\n'
- '\n'
- '\n'
- 'Augmented assignment statements\n'
- '===============================\n'
- '\n'
- 'Augmented assignment is the combination, in a single '
- 'statement, of a\n'
- 'binary operation and an assignment statement:\n'
- '\n'
- ' augmented_assignment_stmt ::= augtarget augop '
- '(expression_list | yield_expression)\n'
- ' augtarget ::= identifier | attributeref | '
- 'subscription | slicing\n'
- ' augop ::= "+=" | "-=" | "*=" | "@=" | '
- '"/=" | "//=" | "%=" | "**="\n'
- ' | ">>=" | "<<=" | "&=" | "^=" | "|="\n'
- '\n'
- '(See section Primaries for the syntax definitions of the last '
- 'three\n'
- 'symbols.)\n'
- '\n'
- 'An augmented assignment evaluates the target (which, unlike '
- 'normal\n'
- 'assignment statements, cannot be an unpacking) and the '
- 'expression\n'
- 'list, performs the binary operation specific to the type of '
- 'assignment\n'
- 'on the two operands, and assigns the result to the original '
- 'target.\n'
- 'The target is only evaluated once.\n'
- '\n'
- 'An augmented assignment statement like "x += 1" can be '
- 'rewritten as "x\n'
- '= x + 1" to achieve a similar, but not exactly equal effect. '
- 'In the\n'
- 'augmented version, "x" is only evaluated once. Also, when '
- 'possible,\n'
- 'the actual operation is performed *in-place*, meaning that '
- 'rather than\n'
- 'creating a new object and assigning that to the target, the '
- 'old object\n'
- 'is modified instead.\n'
- '\n'
- 'Unlike normal assignments, augmented assignments evaluate the '
- 'left-\n'
- 'hand side *before* evaluating the right-hand side. For '
- 'example, "a[i]\n'
- '+= f(x)" first looks-up "a[i]", then it evaluates "f(x)" and '
- 'performs\n'
- 'the addition, and lastly, it writes the result back to '
- '"a[i]".\n'
- '\n'
- 'With the exception of assigning to tuples and multiple targets '
- 'in a\n'
- 'single statement, the assignment done by augmented assignment\n'
- 'statements is handled the same way as normal assignments. '
- 'Similarly,\n'
- 'with the exception of the possible *in-place* behavior, the '
- 'binary\n'
- 'operation performed by augmented assignment is the same as the '
- 'normal\n'
- 'binary operations.\n'
- '\n'
- 'For targets which are attribute references, the same caveat '
- 'about\n'
- 'class and instance attributes applies as for regular '
- 'assignments.\n'
- '\n'
- '\n'
- 'Annotated assignment statements\n'
- '===============================\n'
- '\n'
- '*Annotation* assignment is the combination, in a single '
- 'statement, of\n'
- 'a variable or attribute annotation and an optional assignment\n'
- 'statement:\n'
- '\n'
- ' annotated_assignment_stmt ::= augtarget ":" expression\n'
- ' ["=" (starred_expression | '
- 'yield_expression)]\n'
- '\n'
- 'The difference from normal Assignment statements is that only '
- 'a single\n'
- 'target is allowed.\n'
- '\n'
- 'The assignment target is considered “simple” if it consists of '
- 'a\n'
- 'single name that is not enclosed in parentheses. For simple '
- 'assignment\n'
- 'targets, if in class or module scope, the annotations are '
- 'evaluated\n'
- 'and stored in a special class or module attribute '
- '"__annotations__"\n'
- 'that is a dictionary mapping from variable names (mangled if '
- 'private)\n'
- 'to evaluated annotations. This attribute is writable and is\n'
- 'automatically created at the start of class or module body '
- 'execution,\n'
- 'if annotations are found statically.\n'
- '\n'
- 'If the assignment target is not simple (an attribute, '
- 'subscript node,\n'
- 'or parenthesized name), the annotation is evaluated if in '
- 'class or\n'
- 'module scope, but not stored.\n'
- '\n'
- 'If a name is annotated in a function scope, then this name is '
- 'local\n'
- 'for that scope. Annotations are never evaluated and stored in '
- 'function\n'
- 'scopes.\n'
- '\n'
- 'If the right hand side is present, an annotated assignment '
- 'performs\n'
- 'the actual assignment before evaluating annotations (where\n'
- 'applicable). If the right hand side is not present for an '
- 'expression\n'
- 'target, then the interpreter evaluates the target except for '
- 'the last\n'
- '"__setitem__()" or "__setattr__()" call.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 526** - Syntax for Variable Annotations\n'
- ' The proposal that added syntax for annotating the types '
- 'of\n'
- ' variables (including class variables and instance '
- 'variables),\n'
- ' instead of expressing them through comments.\n'
- '\n'
- ' **PEP 484** - Type hints\n'
- ' The proposal that added the "typing" module to provide a '
- 'standard\n'
- ' syntax for type annotations that can be used in static '
- 'analysis\n'
- ' tools and IDEs.\n'
- '\n'
- 'Changed in version 3.8: Now annotated assignments allow the '
- 'same\n'
- 'expressions in the right hand side as regular assignments. '
- 'Previously,\n'
- 'some expressions (like un-parenthesized tuple expressions) '
- 'caused a\n'
- 'syntax error.\n',
- 'async': 'Coroutines\n'
- '**********\n'
- '\n'
- 'Added in version 3.5.\n'
- '\n'
- '\n'
- 'Coroutine function definition\n'
- '=============================\n'
- '\n'
- ' async_funcdef ::= [decorators] "async" "def" funcname "(" '
- '[parameter_list] ")"\n'
- ' ["->" expression] ":" suite\n'
- '\n'
- 'Execution of Python coroutines can be suspended and resumed at '
- 'many\n'
- 'points (see *coroutine*). "await" expressions, "async for" and '
- '"async\n'
- 'with" can only be used in the body of a coroutine function.\n'
- '\n'
- 'Functions defined with "async def" syntax are always coroutine\n'
- 'functions, even if they do not contain "await" or "async" '
- 'keywords.\n'
- '\n'
- 'It is a "SyntaxError" to use a "yield from" expression inside the '
- 'body\n'
- 'of a coroutine function.\n'
- '\n'
- 'An example of a coroutine function:\n'
- '\n'
- ' async def func(param1, param2):\n'
- ' do_stuff()\n'
- ' await some_coroutine()\n'
- '\n'
- 'Changed in version 3.7: "await" and "async" are now keywords;\n'
- 'previously they were only treated as such inside the body of a\n'
- 'coroutine function.\n'
- '\n'
- '\n'
- 'The "async for" statement\n'
- '=========================\n'
- '\n'
- ' async_for_stmt ::= "async" for_stmt\n'
- '\n'
- 'An *asynchronous iterable* provides an "__aiter__" method that\n'
- 'directly returns an *asynchronous iterator*, which can call\n'
- 'asynchronous code in its "__anext__" method.\n'
- '\n'
- 'The "async for" statement allows convenient iteration over\n'
- 'asynchronous iterables.\n'
- '\n'
- 'The following code:\n'
- '\n'
- ' async for TARGET in ITER:\n'
- ' SUITE\n'
- ' else:\n'
- ' SUITE2\n'
- '\n'
- 'Is semantically equivalent to:\n'
- '\n'
- ' iter = (ITER)\n'
- ' iter = type(iter).__aiter__(iter)\n'
- ' running = True\n'
- '\n'
- ' while running:\n'
- ' try:\n'
- ' TARGET = await type(iter).__anext__(iter)\n'
- ' except StopAsyncIteration:\n'
- ' running = False\n'
- ' else:\n'
- ' SUITE\n'
- ' else:\n'
- ' SUITE2\n'
- '\n'
- 'See also "__aiter__()" and "__anext__()" for details.\n'
- '\n'
- 'It is a "SyntaxError" to use an "async for" statement outside the '
- 'body\n'
- 'of a coroutine function.\n'
- '\n'
- '\n'
- 'The "async with" statement\n'
- '==========================\n'
- '\n'
- ' async_with_stmt ::= "async" with_stmt\n'
- '\n'
- 'An *asynchronous context manager* is a *context manager* that is '
- 'able\n'
- 'to suspend execution in its *enter* and *exit* methods.\n'
- '\n'
- 'The following code:\n'
- '\n'
- ' async with EXPRESSION as TARGET:\n'
- ' SUITE\n'
- '\n'
- 'is semantically equivalent to:\n'
- '\n'
- ' manager = (EXPRESSION)\n'
- ' aenter = type(manager).__aenter__\n'
- ' aexit = type(manager).__aexit__\n'
- ' value = await aenter(manager)\n'
- ' hit_except = False\n'
- '\n'
- ' try:\n'
- ' TARGET = value\n'
- ' SUITE\n'
- ' except:\n'
- ' hit_except = True\n'
- ' if not await aexit(manager, *sys.exc_info()):\n'
- ' raise\n'
- ' finally:\n'
- ' if not hit_except:\n'
- ' await aexit(manager, None, None, None)\n'
- '\n'
- 'See also "__aenter__()" and "__aexit__()" for details.\n'
- '\n'
- 'It is a "SyntaxError" to use an "async with" statement outside the\n'
- 'body of a coroutine function.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 492** - Coroutines with async and await syntax\n'
- ' The proposal that made coroutines a proper standalone concept '
- 'in\n'
- ' Python, and added supporting syntax.\n',
- 'atom-identifiers': 'Identifiers (Names)\n'
- '*******************\n'
- '\n'
- 'An identifier occurring as an atom is a name. See '
- 'section Identifiers\n'
- 'and keywords for lexical definition and section Naming '
- 'and binding for\n'
- 'documentation of naming and binding.\n'
- '\n'
- 'When the name is bound to an object, evaluation of the '
- 'atom yields\n'
- 'that object. When a name is not bound, an attempt to '
- 'evaluate it\n'
- 'raises a "NameError" exception.\n'
- '\n'
- '\n'
- 'Private name mangling\n'
- '=====================\n'
- '\n'
- 'When an identifier that textually occurs in a class '
- 'definition begins\n'
- 'with two or more underscore characters and does not end '
- 'in two or more\n'
- 'underscores, it is considered a *private name* of that '
- 'class.\n'
- '\n'
- 'See also: The class specifications.\n'
- '\n'
- 'More precisely, private names are transformed to a '
- 'longer form before\n'
- 'code is generated for them. If the transformed name is '
- 'longer than\n'
- '255 characters, implementation-defined truncation may '
- 'happen.\n'
- '\n'
- 'The transformation is independent of the syntactical '
- 'context in which\n'
- 'the identifier is used but only the following private '
- 'identifiers are\n'
- 'mangled:\n'
- '\n'
- '* Any name used as the name of a variable that is '
- 'assigned or read or\n'
- ' any name of an attribute being accessed.\n'
- '\n'
- ' The "__name__" attribute of nested functions, classes, '
- 'and type\n'
- ' aliases is however not mangled.\n'
- '\n'
- '* The name of imported modules, e.g., "__spam" in '
- '"import __spam". If\n'
- ' the module is part of a package (i.e., its name '
- 'contains a dot), the\n'
- ' name is *not* mangled, e.g., the "__foo" in "import '
- '__foo.bar" is\n'
- ' not mangled.\n'
- '\n'
- '* The name of an imported member, e.g., "__f" in "from '
- 'spam import\n'
- ' __f".\n'
- '\n'
- 'The transformation rule is defined as follows:\n'
- '\n'
- '* The class name, with leading underscores removed and a '
- 'single\n'
- ' leading underscore inserted, is inserted in front of '
- 'the identifier,\n'
- ' e.g., the identifier "__spam" occurring in a class '
- 'named "Foo",\n'
- ' "_Foo" or "__Foo" is transformed to "_Foo__spam".\n'
- '\n'
- '* If the class name consists only of underscores, the '
- 'transformation\n'
- ' is the identity, e.g., the identifier "__spam" '
- 'occurring in a class\n'
- ' named "_" or "__" is left as is.\n',
- 'atom-literals': 'Literals\n'
- '********\n'
- '\n'
- 'Python supports string and bytes literals and various '
- 'numeric\n'
- 'literals:\n'
- '\n'
- ' literal ::= stringliteral | bytesliteral\n'
- ' | integer | floatnumber | imagnumber\n'
- '\n'
- 'Evaluation of a literal yields an object of the given type '
- '(string,\n'
- 'bytes, integer, floating-point number, complex number) with '
- 'the given\n'
- 'value. The value may be approximated in the case of '
- 'floating-point\n'
- 'and imaginary (complex) literals. See section Literals for '
- 'details.\n'
- '\n'
- 'All literals correspond to immutable data types, and hence '
- 'the\n'
- 'object’s identity is less important than its value. '
- 'Multiple\n'
- 'evaluations of literals with the same value (either the '
- 'same\n'
- 'occurrence in the program text or a different occurrence) '
- 'may obtain\n'
- 'the same object or a different object with the same '
- 'value.\n',
- 'attribute-access': 'Customizing attribute access\n'
- '****************************\n'
- '\n'
- 'The following methods can be defined to customize the '
- 'meaning of\n'
- 'attribute access (use of, assignment to, or deletion of '
- '"x.name") for\n'
- 'class instances.\n'
- '\n'
- 'object.__getattr__(self, name)\n'
- '\n'
- ' Called when the default attribute access fails with '
- 'an\n'
- ' "AttributeError" (either "__getattribute__()" raises '
- 'an\n'
- ' "AttributeError" because *name* is not an instance '
- 'attribute or an\n'
- ' attribute in the class tree for "self"; or '
- '"__get__()" of a *name*\n'
- ' property raises "AttributeError"). This method '
- 'should either\n'
- ' return the (computed) attribute value or raise an '
- '"AttributeError"\n'
- ' exception. The "object" class itself does not provide '
- 'this method.\n'
- '\n'
- ' Note that if the attribute is found through the '
- 'normal mechanism,\n'
- ' "__getattr__()" is not called. (This is an '
- 'intentional asymmetry\n'
- ' between "__getattr__()" and "__setattr__()".) This is '
- 'done both for\n'
- ' efficiency reasons and because otherwise '
- '"__getattr__()" would have\n'
- ' no way to access other attributes of the instance. '
- 'Note that at\n'
- ' least for instance variables, you can fake total '
- 'control by not\n'
- ' inserting any values in the instance attribute '
- 'dictionary (but\n'
- ' instead inserting them in another object). See the\n'
- ' "__getattribute__()" method below for a way to '
- 'actually get total\n'
- ' control over attribute access.\n'
- '\n'
- 'object.__getattribute__(self, name)\n'
- '\n'
- ' Called unconditionally to implement attribute '
- 'accesses for\n'
- ' instances of the class. If the class also defines '
- '"__getattr__()",\n'
- ' the latter will not be called unless '
- '"__getattribute__()" either\n'
- ' calls it explicitly or raises an "AttributeError". '
- 'This method\n'
- ' should return the (computed) attribute value or raise '
- 'an\n'
- ' "AttributeError" exception. In order to avoid '
- 'infinite recursion in\n'
- ' this method, its implementation should always call '
- 'the base class\n'
- ' method with the same name to access any attributes it '
- 'needs, for\n'
- ' example, "object.__getattribute__(self, name)".\n'
- '\n'
- ' Note:\n'
- '\n'
- ' This method may still be bypassed when looking up '
- 'special methods\n'
- ' as the result of implicit invocation via language '
- 'syntax or\n'
- ' built-in functions. See Special method lookup.\n'
- '\n'
- ' For certain sensitive attribute accesses, raises an '
- 'auditing event\n'
- ' "object.__getattr__" with arguments "obj" and '
- '"name".\n'
- '\n'
- 'object.__setattr__(self, name, value)\n'
- '\n'
- ' Called when an attribute assignment is attempted. '
- 'This is called\n'
- ' instead of the normal mechanism (i.e. store the value '
- 'in the\n'
- ' instance dictionary). *name* is the attribute name, '
- '*value* is the\n'
- ' value to be assigned to it.\n'
- '\n'
- ' If "__setattr__()" wants to assign to an instance '
- 'attribute, it\n'
- ' should call the base class method with the same name, '
- 'for example,\n'
- ' "object.__setattr__(self, name, value)".\n'
- '\n'
- ' For certain sensitive attribute assignments, raises '
- 'an auditing\n'
- ' event "object.__setattr__" with arguments "obj", '
- '"name", "value".\n'
- '\n'
- 'object.__delattr__(self, name)\n'
- '\n'
- ' Like "__setattr__()" but for attribute deletion '
- 'instead of\n'
- ' assignment. This should only be implemented if "del '
- 'obj.name" is\n'
- ' meaningful for the object.\n'
- '\n'
- ' For certain sensitive attribute deletions, raises an '
- 'auditing event\n'
- ' "object.__delattr__" with arguments "obj" and '
- '"name".\n'
- '\n'
- 'object.__dir__(self)\n'
- '\n'
- ' Called when "dir()" is called on the object. An '
- 'iterable must be\n'
- ' returned. "dir()" converts the returned iterable to a '
- 'list and\n'
- ' sorts it.\n'
- '\n'
- '\n'
- 'Customizing module attribute access\n'
- '===================================\n'
- '\n'
- 'Special names "__getattr__" and "__dir__" can be also '
- 'used to\n'
- 'customize access to module attributes. The "__getattr__" '
- 'function at\n'
- 'the module level should accept one argument which is the '
- 'name of an\n'
- 'attribute and return the computed value or raise an '
- '"AttributeError".\n'
- 'If an attribute is not found on a module object through '
- 'the normal\n'
- 'lookup, i.e. "object.__getattribute__()", then '
- '"__getattr__" is\n'
- 'searched in the module "__dict__" before raising an '
- '"AttributeError".\n'
- 'If found, it is called with the attribute name and the '
- 'result is\n'
- 'returned.\n'
- '\n'
- 'The "__dir__" function should accept no arguments, and '
- 'return an\n'
- 'iterable of strings that represents the names accessible '
- 'on module. If\n'
- 'present, this function overrides the standard "dir()" '
- 'search on a\n'
- 'module.\n'
- '\n'
- 'For a more fine grained customization of the module '
- 'behavior (setting\n'
- 'attributes, properties, etc.), one can set the '
- '"__class__" attribute\n'
- 'of a module object to a subclass of "types.ModuleType". '
- 'For example:\n'
- '\n'
- ' import sys\n'
- ' from types import ModuleType\n'
- '\n'
- ' class VerboseModule(ModuleType):\n'
- ' def __repr__(self):\n'
- " return f'Verbose {self.__name__}'\n"
- '\n'
- ' def __setattr__(self, attr, value):\n'
- " print(f'Setting {attr}...')\n"
- ' super().__setattr__(attr, value)\n'
- '\n'
- ' sys.modules[__name__].__class__ = VerboseModule\n'
- '\n'
- 'Note:\n'
- '\n'
- ' Defining module "__getattr__" and setting module '
- '"__class__" only\n'
- ' affect lookups made using the attribute access syntax '
- '– directly\n'
- ' accessing the module globals (whether by code within '
- 'the module, or\n'
- ' via a reference to the module’s globals dictionary) is '
- 'unaffected.\n'
- '\n'
- 'Changed in version 3.5: "__class__" module attribute is '
- 'now writable.\n'
- '\n'
- 'Added in version 3.7: "__getattr__" and "__dir__" module '
- 'attributes.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 562** - Module __getattr__ and __dir__\n'
- ' Describes the "__getattr__" and "__dir__" functions '
- 'on modules.\n'
- '\n'
- '\n'
- 'Implementing Descriptors\n'
- '========================\n'
- '\n'
- 'The following methods only apply when an instance of the '
- 'class\n'
- 'containing the method (a so-called *descriptor* class) '
- 'appears in an\n'
- '*owner* class (the descriptor must be in either the '
- 'owner’s class\n'
- 'dictionary or in the class dictionary for one of its '
- 'parents). In the\n'
- 'examples below, “the attribute” refers to the attribute '
- 'whose name is\n'
- 'the key of the property in the owner class’ "__dict__". '
- 'The "object"\n'
- 'class itself does not implement any of these protocols.\n'
- '\n'
- 'object.__get__(self, instance, owner=None)\n'
- '\n'
- ' Called to get the attribute of the owner class (class '
- 'attribute\n'
- ' access) or of an instance of that class (instance '
- 'attribute\n'
- ' access). The optional *owner* argument is the owner '
- 'class, while\n'
- ' *instance* is the instance that the attribute was '
- 'accessed through,\n'
- ' or "None" when the attribute is accessed through the '
- '*owner*.\n'
- '\n'
- ' This method should return the computed attribute '
- 'value or raise an\n'
- ' "AttributeError" exception.\n'
- '\n'
- ' **PEP 252** specifies that "__get__()" is callable '
- 'with one or two\n'
- ' arguments. Python’s own built-in descriptors support '
- 'this\n'
- ' specification; however, it is likely that some '
- 'third-party tools\n'
- ' have descriptors that require both arguments. '
- 'Python’s own\n'
- ' "__getattribute__()" implementation always passes in '
- 'both arguments\n'
- ' whether they are required or not.\n'
- '\n'
- 'object.__set__(self, instance, value)\n'
- '\n'
- ' Called to set the attribute on an instance *instance* '
- 'of the owner\n'
- ' class to a new value, *value*.\n'
- '\n'
- ' Note, adding "__set__()" or "__delete__()" changes '
- 'the kind of\n'
- ' descriptor to a “data descriptor”. See Invoking '
- 'Descriptors for\n'
- ' more details.\n'
- '\n'
- 'object.__delete__(self, instance)\n'
- '\n'
- ' Called to delete the attribute on an instance '
- '*instance* of the\n'
- ' owner class.\n'
- '\n'
- 'Instances of descriptors may also have the '
- '"__objclass__" attribute\n'
- 'present:\n'
- '\n'
- 'object.__objclass__\n'
- '\n'
- ' The attribute "__objclass__" is interpreted by the '
- '"inspect" module\n'
- ' as specifying the class where this object was defined '
- '(setting this\n'
- ' appropriately can assist in runtime introspection of '
- 'dynamic class\n'
- ' attributes). For callables, it may indicate that an '
- 'instance of the\n'
- ' given type (or a subclass) is expected or required as '
- 'the first\n'
- ' positional argument (for example, CPython sets this '
- 'attribute for\n'
- ' unbound methods that are implemented in C).\n'
- '\n'
- '\n'
- 'Invoking Descriptors\n'
- '====================\n'
- '\n'
- 'In general, a descriptor is an object attribute with '
- '“binding\n'
- 'behavior”, one whose attribute access has been '
- 'overridden by methods\n'
- 'in the descriptor protocol: "__get__()", "__set__()", '
- 'and\n'
- '"__delete__()". If any of those methods are defined for '
- 'an object, it\n'
- 'is said to be a descriptor.\n'
- '\n'
- 'The default behavior for attribute access is to get, '
- 'set, or delete\n'
- 'the attribute from an object’s dictionary. For instance, '
- '"a.x" has a\n'
- 'lookup chain starting with "a.__dict__[\'x\']", then\n'
- '"type(a).__dict__[\'x\']", and continuing through the '
- 'base classes of\n'
- '"type(a)" excluding metaclasses.\n'
- '\n'
- 'However, if the looked-up value is an object defining '
- 'one of the\n'
- 'descriptor methods, then Python may override the default '
- 'behavior and\n'
- 'invoke the descriptor method instead. Where this occurs '
- 'in the\n'
- 'precedence chain depends on which descriptor methods '
- 'were defined and\n'
- 'how they were called.\n'
- '\n'
- 'The starting point for descriptor invocation is a '
- 'binding, "a.x". How\n'
- 'the arguments are assembled depends on "a":\n'
- '\n'
- 'Direct Call\n'
- ' The simplest and least common call is when user code '
- 'directly\n'
- ' invokes a descriptor method: "x.__get__(a)".\n'
- '\n'
- 'Instance Binding\n'
- ' If binding to an object instance, "a.x" is '
- 'transformed into the\n'
- ' call: "type(a).__dict__[\'x\'].__get__(a, type(a))".\n'
- '\n'
- 'Class Binding\n'
- ' If binding to a class, "A.x" is transformed into the '
- 'call:\n'
- ' "A.__dict__[\'x\'].__get__(None, A)".\n'
- '\n'
- 'Super Binding\n'
- ' A dotted lookup such as "super(A, a).x" searches\n'
- ' "a.__class__.__mro__" for a base class "B" following '
- '"A" and then\n'
- ' returns "B.__dict__[\'x\'].__get__(a, A)". If not a '
- 'descriptor, "x"\n'
- ' is returned unchanged.\n'
- '\n'
- 'For instance bindings, the precedence of descriptor '
- 'invocation depends\n'
- 'on which descriptor methods are defined. A descriptor '
- 'can define any\n'
- 'combination of "__get__()", "__set__()" and '
- '"__delete__()". If it\n'
- 'does not define "__get__()", then accessing the '
- 'attribute will return\n'
- 'the descriptor object itself unless there is a value in '
- 'the object’s\n'
- 'instance dictionary. If the descriptor defines '
- '"__set__()" and/or\n'
- '"__delete__()", it is a data descriptor; if it defines '
- 'neither, it is\n'
- 'a non-data descriptor. Normally, data descriptors '
- 'define both\n'
- '"__get__()" and "__set__()", while non-data descriptors '
- 'have just the\n'
- '"__get__()" method. Data descriptors with "__get__()" '
- 'and "__set__()"\n'
- '(and/or "__delete__()") defined always override a '
- 'redefinition in an\n'
- 'instance dictionary. In contrast, non-data descriptors '
- 'can be\n'
- 'overridden by instances.\n'
- '\n'
- 'Python methods (including those decorated with '
- '"@staticmethod" and\n'
- '"@classmethod") are implemented as non-data '
- 'descriptors. Accordingly,\n'
- 'instances can redefine and override methods. This '
- 'allows individual\n'
- 'instances to acquire behaviors that differ from other '
- 'instances of the\n'
- 'same class.\n'
- '\n'
- 'The "property()" function is implemented as a data '
- 'descriptor.\n'
- 'Accordingly, instances cannot override the behavior of a '
- 'property.\n'
- '\n'
- '\n'
- '__slots__\n'
- '=========\n'
- '\n'
- '*__slots__* allow us to explicitly declare data members '
- '(like\n'
- 'properties) and deny the creation of "__dict__" and '
- '*__weakref__*\n'
- '(unless explicitly declared in *__slots__* or available '
- 'in a parent.)\n'
- '\n'
- 'The space saved over using "__dict__" can be '
- 'significant. Attribute\n'
- 'lookup speed can be significantly improved as well.\n'
- '\n'
- 'object.__slots__\n'
- '\n'
- ' This class variable can be assigned a string, '
- 'iterable, or sequence\n'
- ' of strings with variable names used by instances. '
- '*__slots__*\n'
- ' reserves space for the declared variables and '
- 'prevents the\n'
- ' automatic creation of "__dict__" and *__weakref__* '
- 'for each\n'
- ' instance.\n'
- '\n'
- 'Notes on using *__slots__*:\n'
- '\n'
- '* When inheriting from a class without *__slots__*, the '
- '"__dict__" and\n'
- ' *__weakref__* attribute of the instances will always '
- 'be accessible.\n'
- '\n'
- '* Without a "__dict__" variable, instances cannot be '
- 'assigned new\n'
- ' variables not listed in the *__slots__* definition. '
- 'Attempts to\n'
- ' assign to an unlisted variable name raises '
- '"AttributeError". If\n'
- ' dynamic assignment of new variables is desired, then '
- 'add\n'
- ' "\'__dict__\'" to the sequence of strings in the '
- '*__slots__*\n'
- ' declaration.\n'
- '\n'
- '* Without a *__weakref__* variable for each instance, '
- 'classes defining\n'
- ' *__slots__* do not support "weak references" to its '
- 'instances. If\n'
- ' weak reference support is needed, then add '
- '"\'__weakref__\'" to the\n'
- ' sequence of strings in the *__slots__* declaration.\n'
- '\n'
- '* *__slots__* are implemented at the class level by '
- 'creating\n'
- ' descriptors for each variable name. As a result, '
- 'class attributes\n'
- ' cannot be used to set default values for instance '
- 'variables defined\n'
- ' by *__slots__*; otherwise, the class attribute would '
- 'overwrite the\n'
- ' descriptor assignment.\n'
- '\n'
- '* The action of a *__slots__* declaration is not limited '
- 'to the class\n'
- ' where it is defined. *__slots__* declared in parents '
- 'are available\n'
- ' in child classes. However, instances of a child '
- 'subclass will get a\n'
- ' "__dict__" and *__weakref__* unless the subclass also '
- 'defines\n'
- ' *__slots__* (which should only contain names of any '
- '*additional*\n'
- ' slots).\n'
- '\n'
- '* If a class defines a slot also defined in a base '
- 'class, the instance\n'
- ' variable defined by the base class slot is '
- 'inaccessible (except by\n'
- ' retrieving its descriptor directly from the base '
- 'class). This\n'
- ' renders the meaning of the program undefined. In the '
- 'future, a\n'
- ' check may be added to prevent this.\n'
- '\n'
- '* "TypeError" will be raised if nonempty *__slots__* are '
- 'defined for a\n'
- ' class derived from a ""variable-length" built-in type" '
- 'such as\n'
- ' "int", "bytes", and "tuple".\n'
- '\n'
- '* Any non-string *iterable* may be assigned to '
- '*__slots__*.\n'
- '\n'
- '* If a "dictionary" is used to assign *__slots__*, the '
- 'dictionary keys\n'
- ' will be used as the slot names. The values of the '
- 'dictionary can be\n'
- ' used to provide per-attribute docstrings that will be '
- 'recognised by\n'
- ' "inspect.getdoc()" and displayed in the output of '
- '"help()".\n'
- '\n'
- '* "__class__" assignment works only if both classes have '
- 'the same\n'
- ' *__slots__*.\n'
- '\n'
- '* Multiple inheritance with multiple slotted parent '
- 'classes can be\n'
- ' used, but only one parent is allowed to have '
- 'attributes created by\n'
- ' slots (the other bases must have empty slot layouts) - '
- 'violations\n'
- ' raise "TypeError".\n'
- '\n'
- '* If an *iterator* is used for *__slots__* then a '
- '*descriptor* is\n'
- ' created for each of the iterator’s values. However, '
- 'the *__slots__*\n'
- ' attribute will be an empty iterator.\n',
- 'attribute-references': 'Attribute references\n'
- '********************\n'
- '\n'
- 'An attribute reference is a primary followed by a '
- 'period and a name:\n'
- '\n'
- ' attributeref ::= primary "." identifier\n'
- '\n'
- 'The primary must evaluate to an object of a type '
- 'that supports\n'
- 'attribute references, which most objects do. This '
- 'object is then\n'
- 'asked to produce the attribute whose name is the '
- 'identifier. The type\n'
- 'and value produced is determined by the object. '
- 'Multiple evaluations\n'
- 'of the same attribute reference may yield different '
- 'objects.\n'
- '\n'
- 'This production can be customized by overriding the\n'
- '"__getattribute__()" method or the "__getattr__()" '
- 'method. The\n'
- '"__getattribute__()" method is called first and '
- 'either returns a value\n'
- 'or raises "AttributeError" if the attribute is not '
- 'available.\n'
- '\n'
- 'If an "AttributeError" is raised and the object has '
- 'a "__getattr__()"\n'
- 'method, that method is called as a fallback.\n',
- 'augassign': 'Augmented assignment statements\n'
- '*******************************\n'
- '\n'
- 'Augmented assignment is the combination, in a single statement, '
- 'of a\n'
- 'binary operation and an assignment statement:\n'
- '\n'
- ' augmented_assignment_stmt ::= augtarget augop '
- '(expression_list | yield_expression)\n'
- ' augtarget ::= identifier | attributeref | '
- 'subscription | slicing\n'
- ' augop ::= "+=" | "-=" | "*=" | "@=" | '
- '"/=" | "//=" | "%=" | "**="\n'
- ' | ">>=" | "<<=" | "&=" | "^=" | "|="\n'
- '\n'
- '(See section Primaries for the syntax definitions of the last '
- 'three\n'
- 'symbols.)\n'
- '\n'
- 'An augmented assignment evaluates the target (which, unlike '
- 'normal\n'
- 'assignment statements, cannot be an unpacking) and the '
- 'expression\n'
- 'list, performs the binary operation specific to the type of '
- 'assignment\n'
- 'on the two operands, and assigns the result to the original '
- 'target.\n'
- 'The target is only evaluated once.\n'
- '\n'
- 'An augmented assignment statement like "x += 1" can be '
- 'rewritten as "x\n'
- '= x + 1" to achieve a similar, but not exactly equal effect. In '
- 'the\n'
- 'augmented version, "x" is only evaluated once. Also, when '
- 'possible,\n'
- 'the actual operation is performed *in-place*, meaning that '
- 'rather than\n'
- 'creating a new object and assigning that to the target, the old '
- 'object\n'
- 'is modified instead.\n'
- '\n'
- 'Unlike normal assignments, augmented assignments evaluate the '
- 'left-\n'
- 'hand side *before* evaluating the right-hand side. For '
- 'example, "a[i]\n'
- '+= f(x)" first looks-up "a[i]", then it evaluates "f(x)" and '
- 'performs\n'
- 'the addition, and lastly, it writes the result back to "a[i]".\n'
- '\n'
- 'With the exception of assigning to tuples and multiple targets '
- 'in a\n'
- 'single statement, the assignment done by augmented assignment\n'
- 'statements is handled the same way as normal assignments. '
- 'Similarly,\n'
- 'with the exception of the possible *in-place* behavior, the '
- 'binary\n'
- 'operation performed by augmented assignment is the same as the '
- 'normal\n'
- 'binary operations.\n'
- '\n'
- 'For targets which are attribute references, the same caveat '
- 'about\n'
- 'class and instance attributes applies as for regular '
- 'assignments.\n',
- 'await': 'Await expression\n'
- '****************\n'
- '\n'
- 'Suspend the execution of *coroutine* on an *awaitable* object. Can\n'
- 'only be used inside a *coroutine function*.\n'
- '\n'
- ' await_expr ::= "await" primary\n'
- '\n'
- 'Added in version 3.5.\n',
- 'binary': 'Binary arithmetic operations\n'
- '****************************\n'
- '\n'
- 'The binary arithmetic operations have the conventional priority\n'
- 'levels. Note that some of these operations also apply to certain '
- 'non-\n'
- 'numeric types. Apart from the power operator, there are only two\n'
- 'levels, one for multiplicative operators and one for additive\n'
- 'operators:\n'
- '\n'
- ' m_expr ::= u_expr | m_expr "*" u_expr | m_expr "@" m_expr |\n'
- ' m_expr "//" u_expr | m_expr "/" u_expr |\n'
- ' m_expr "%" u_expr\n'
- ' a_expr ::= m_expr | a_expr "+" m_expr | a_expr "-" m_expr\n'
- '\n'
- 'The "*" (multiplication) operator yields the product of its '
- 'arguments.\n'
- 'The arguments must either both be numbers, or one argument must be '
- 'an\n'
- 'integer and the other must be a sequence. In the former case, the\n'
- 'numbers are converted to a common type and then multiplied '
- 'together.\n'
- 'In the latter case, sequence repetition is performed; a negative\n'
- 'repetition factor yields an empty sequence.\n'
- '\n'
- 'This operation can be customized using the special "__mul__()" '
- 'and\n'
- '"__rmul__()" methods.\n'
- '\n'
- 'The "@" (at) operator is intended to be used for matrix\n'
- 'multiplication. No builtin Python types implement this operator.\n'
- '\n'
- 'This operation can be customized using the special "__matmul__()" '
- 'and\n'
- '"__rmatmul__()" methods.\n'
- '\n'
- 'Added in version 3.5.\n'
- '\n'
- 'The "/" (division) and "//" (floor division) operators yield the\n'
- 'quotient of their arguments. The numeric arguments are first\n'
- 'converted to a common type. Division of integers yields a float, '
- 'while\n'
- 'floor division of integers results in an integer; the result is '
- 'that\n'
- 'of mathematical division with the ‘floor’ function applied to the\n'
- 'result. Division by zero raises the "ZeroDivisionError" '
- 'exception.\n'
- '\n'
- 'The division operation can be customized using the special\n'
- '"__truediv__()" and "__rtruediv__()" methods. The floor division\n'
- 'operation can be customized using the special "__floordiv__()" '
- 'and\n'
- '"__rfloordiv__()" methods.\n'
- '\n'
- 'The "%" (modulo) operator yields the remainder from the division '
- 'of\n'
- 'the first argument by the second. The numeric arguments are '
- 'first\n'
- 'converted to a common type. A zero right argument raises the\n'
- '"ZeroDivisionError" exception. The arguments may be '
- 'floating-point\n'
- 'numbers, e.g., "3.14%0.7" equals "0.34" (since "3.14" equals '
- '"4*0.7 +\n'
- '0.34".) The modulo operator always yields a result with the same '
- 'sign\n'
- 'as its second operand (or zero); the absolute value of the result '
- 'is\n'
- 'strictly smaller than the absolute value of the second operand '
- '[1].\n'
- '\n'
- 'The floor division and modulo operators are connected by the '
- 'following\n'
- 'identity: "x == (x//y)*y + (x%y)". Floor division and modulo are '
- 'also\n'
- 'connected with the built-in function "divmod()": "divmod(x, y) ==\n'
- '(x//y, x%y)". [2].\n'
- '\n'
- 'In addition to performing the modulo operation on numbers, the '
- '"%"\n'
- 'operator is also overloaded by string objects to perform '
- 'old-style\n'
- 'string formatting (also known as interpolation). The syntax for\n'
- 'string formatting is described in the Python Library Reference,\n'
- 'section printf-style String Formatting.\n'
- '\n'
- 'The *modulo* operation can be customized using the special '
- '"__mod__()"\n'
- 'and "__rmod__()" methods.\n'
- '\n'
- 'The floor division operator, the modulo operator, and the '
- '"divmod()"\n'
- 'function are not defined for complex numbers. Instead, convert to '
- 'a\n'
- 'floating-point number using the "abs()" function if appropriate.\n'
- '\n'
- 'The "+" (addition) operator yields the sum of its arguments. The\n'
- 'arguments must either both be numbers or both be sequences of the '
- 'same\n'
- 'type. In the former case, the numbers are converted to a common '
- 'type\n'
- 'and then added together. In the latter case, the sequences are\n'
- 'concatenated.\n'
- '\n'
- 'This operation can be customized using the special "__add__()" '
- 'and\n'
- '"__radd__()" methods.\n'
- '\n'
- 'The "-" (subtraction) operator yields the difference of its '
- 'arguments.\n'
- 'The numeric arguments are first converted to a common type.\n'
- '\n'
- 'This operation can be customized using the special "__sub__()" '
- 'and\n'
- '"__rsub__()" methods.\n',
- 'bitwise': 'Binary bitwise operations\n'
- '*************************\n'
- '\n'
- 'Each of the three bitwise operations has a different priority '
- 'level:\n'
- '\n'
- ' and_expr ::= shift_expr | and_expr "&" shift_expr\n'
- ' xor_expr ::= and_expr | xor_expr "^" and_expr\n'
- ' or_expr ::= xor_expr | or_expr "|" xor_expr\n'
- '\n'
- 'The "&" operator yields the bitwise AND of its arguments, which '
- 'must\n'
- 'be integers or one of them must be a custom object overriding\n'
- '"__and__()" or "__rand__()" special methods.\n'
- '\n'
- 'The "^" operator yields the bitwise XOR (exclusive OR) of its\n'
- 'arguments, which must be integers or one of them must be a '
- 'custom\n'
- 'object overriding "__xor__()" or "__rxor__()" special methods.\n'
- '\n'
- 'The "|" operator yields the bitwise (inclusive) OR of its '
- 'arguments,\n'
- 'which must be integers or one of them must be a custom object\n'
- 'overriding "__or__()" or "__ror__()" special methods.\n',
- 'bltin-code-objects': 'Code Objects\n'
- '************\n'
- '\n'
- 'Code objects are used by the implementation to '
- 'represent “pseudo-\n'
- 'compiled” executable Python code such as a function '
- 'body. They differ\n'
- 'from function objects because they don’t contain a '
- 'reference to their\n'
- 'global execution environment. Code objects are '
- 'returned by the built-\n'
- 'in "compile()" function and can be extracted from '
- 'function objects\n'
- 'through their "__code__" attribute. See also the '
- '"code" module.\n'
- '\n'
- 'Accessing "__code__" raises an auditing event '
- '"object.__getattr__"\n'
- 'with arguments "obj" and ""__code__"".\n'
- '\n'
- 'A code object can be executed or evaluated by passing '
- 'it (instead of a\n'
- 'source string) to the "exec()" or "eval()" built-in '
- 'functions.\n'
- '\n'
- 'See The standard type hierarchy for more '
- 'information.\n',
- 'bltin-ellipsis-object': 'The Ellipsis Object\n'
- '*******************\n'
- '\n'
- 'This object is commonly used by slicing (see '
- 'Slicings). It supports\n'
- 'no special operations. There is exactly one '
- 'ellipsis object, named\n'
- '"Ellipsis" (a built-in name). "type(Ellipsis)()" '
- 'produces the\n'
- '"Ellipsis" singleton.\n'
- '\n'
- 'It is written as "Ellipsis" or "...".\n',
- 'bltin-null-object': 'The Null Object\n'
- '***************\n'
- '\n'
- 'This object is returned by functions that don’t '
- 'explicitly return a\n'
- 'value. It supports no special operations. There is '
- 'exactly one null\n'
- 'object, named "None" (a built-in name). "type(None)()" '
- 'produces the\n'
- 'same singleton.\n'
- '\n'
- 'It is written as "None".\n',
- 'bltin-type-objects': 'Type Objects\n'
- '************\n'
- '\n'
- 'Type objects represent the various object types. An '
- 'object’s type is\n'
- 'accessed by the built-in function "type()". There are '
- 'no special\n'
- 'operations on types. The standard module "types" '
- 'defines names for\n'
- 'all standard built-in types.\n'
- '\n'
- 'Types are written like this: "<class \'int\'>".\n',
- 'booleans': 'Boolean operations\n'
- '******************\n'
- '\n'
- ' or_test ::= and_test | or_test "or" and_test\n'
- ' and_test ::= not_test | and_test "and" not_test\n'
- ' not_test ::= comparison | "not" not_test\n'
- '\n'
- 'In the context of Boolean operations, and also when expressions '
- 'are\n'
- 'used by control flow statements, the following values are '
- 'interpreted\n'
- 'as false: "False", "None", numeric zero of all types, and empty\n'
- 'strings and containers (including strings, tuples, lists,\n'
- 'dictionaries, sets and frozensets). All other values are '
- 'interpreted\n'
- 'as true. User-defined objects can customize their truth value '
- 'by\n'
- 'providing a "__bool__()" method.\n'
- '\n'
- 'The operator "not" yields "True" if its argument is false, '
- '"False"\n'
- 'otherwise.\n'
- '\n'
- 'The expression "x and y" first evaluates *x*; if *x* is false, '
- 'its\n'
- 'value is returned; otherwise, *y* is evaluated and the resulting '
- 'value\n'
- 'is returned.\n'
- '\n'
- 'The expression "x or y" first evaluates *x*; if *x* is true, its '
- 'value\n'
- 'is returned; otherwise, *y* is evaluated and the resulting value '
- 'is\n'
- 'returned.\n'
- '\n'
- 'Note that neither "and" nor "or" restrict the value and type '
- 'they\n'
- 'return to "False" and "True", but rather return the last '
- 'evaluated\n'
- 'argument. This is sometimes useful, e.g., if "s" is a string '
- 'that\n'
- 'should be replaced by a default value if it is empty, the '
- 'expression\n'
- '"s or \'foo\'" yields the desired value. Because "not" has to '
- 'create a\n'
- 'new value, it returns a boolean value regardless of the type of '
- 'its\n'
- 'argument (for example, "not \'foo\'" produces "False" rather '
- 'than "\'\'".)\n',
- 'break': 'The "break" statement\n'
- '*********************\n'
- '\n'
- ' break_stmt ::= "break"\n'
- '\n'
- '"break" may only occur syntactically nested in a "for" or "while"\n'
- 'loop, but not nested in a function or class definition within that\n'
- 'loop.\n'
- '\n'
- 'It terminates the nearest enclosing loop, skipping the optional '
- '"else"\n'
- 'clause if the loop has one.\n'
- '\n'
- 'If a "for" loop is terminated by "break", the loop control target\n'
- 'keeps its current value.\n'
- '\n'
- 'When "break" passes control out of a "try" statement with a '
- '"finally"\n'
- 'clause, that "finally" clause is executed before really leaving '
- 'the\n'
- 'loop.\n',
- 'callable-types': 'Emulating callable objects\n'
- '**************************\n'
- '\n'
- 'object.__call__(self[, args...])\n'
- '\n'
- ' Called when the instance is “called” as a function; if '
- 'this method\n'
- ' is defined, "x(arg1, arg2, ...)" roughly translates to\n'
- ' "type(x).__call__(x, arg1, ...)". The "object" class '
- 'itself does\n'
- ' not provide this method.\n',
- 'calls': 'Calls\n'
- '*****\n'
- '\n'
- 'A call calls a callable object (e.g., a *function*) with a '
- 'possibly\n'
- 'empty series of *arguments*:\n'
- '\n'
- ' call ::= primary "(" [argument_list [","] | '
- 'comprehension] ")"\n'
- ' argument_list ::= positional_arguments ["," '
- 'starred_and_keywords]\n'
- ' ["," keywords_arguments]\n'
- ' | starred_and_keywords ["," '
- 'keywords_arguments]\n'
- ' | keywords_arguments\n'
- ' positional_arguments ::= positional_item ("," positional_item)*\n'
- ' positional_item ::= assignment_expression | "*" expression\n'
- ' starred_and_keywords ::= ("*" expression | keyword_item)\n'
- ' ("," "*" expression | "," '
- 'keyword_item)*\n'
- ' keywords_arguments ::= (keyword_item | "**" expression)\n'
- ' ("," keyword_item | "," "**" '
- 'expression)*\n'
- ' keyword_item ::= identifier "=" expression\n'
- '\n'
- 'An optional trailing comma may be present after the positional and\n'
- 'keyword arguments but does not affect the semantics.\n'
- '\n'
- 'The primary must evaluate to a callable object (user-defined\n'
- 'functions, built-in functions, methods of built-in objects, class\n'
- 'objects, methods of class instances, and all objects having a\n'
- '"__call__()" method are callable). All argument expressions are\n'
- 'evaluated before the call is attempted. Please refer to section\n'
- 'Function definitions for the syntax of formal *parameter* lists.\n'
- '\n'
- 'If keyword arguments are present, they are first converted to\n'
- 'positional arguments, as follows. First, a list of unfilled slots '
- 'is\n'
- 'created for the formal parameters. If there are N positional\n'
- 'arguments, they are placed in the first N slots. Next, for each\n'
- 'keyword argument, the identifier is used to determine the\n'
- 'corresponding slot (if the identifier is the same as the first '
- 'formal\n'
- 'parameter name, the first slot is used, and so on). If the slot '
- 'is\n'
- 'already filled, a "TypeError" exception is raised. Otherwise, the\n'
- 'argument is placed in the slot, filling it (even if the expression '
- 'is\n'
- '"None", it fills the slot). When all arguments have been '
- 'processed,\n'
- 'the slots that are still unfilled are filled with the '
- 'corresponding\n'
- 'default value from the function definition. (Default values are\n'
- 'calculated, once, when the function is defined; thus, a mutable '
- 'object\n'
- 'such as a list or dictionary used as default value will be shared '
- 'by\n'
- 'all calls that don’t specify an argument value for the '
- 'corresponding\n'
- 'slot; this should usually be avoided.) If there are any unfilled\n'
- 'slots for which no default value is specified, a "TypeError" '
- 'exception\n'
- 'is raised. Otherwise, the list of filled slots is used as the\n'
- 'argument list for the call.\n'
- '\n'
- '**CPython implementation detail:** An implementation may provide\n'
- 'built-in functions whose positional parameters do not have names, '
- 'even\n'
- 'if they are ‘named’ for the purpose of documentation, and which\n'
- 'therefore cannot be supplied by keyword. In CPython, this is the '
- 'case\n'
- 'for functions implemented in C that use "PyArg_ParseTuple()" to '
- 'parse\n'
- 'their arguments.\n'
- '\n'
- 'If there are more positional arguments than there are formal '
- 'parameter\n'
- 'slots, a "TypeError" exception is raised, unless a formal '
- 'parameter\n'
- 'using the syntax "*identifier" is present; in this case, that '
- 'formal\n'
- 'parameter receives a tuple containing the excess positional '
- 'arguments\n'
- '(or an empty tuple if there were no excess positional arguments).\n'
- '\n'
- 'If any keyword argument does not correspond to a formal parameter\n'
- 'name, a "TypeError" exception is raised, unless a formal parameter\n'
- 'using the syntax "**identifier" is present; in this case, that '
- 'formal\n'
- 'parameter receives a dictionary containing the excess keyword\n'
- 'arguments (using the keywords as keys and the argument values as\n'
- 'corresponding values), or a (new) empty dictionary if there were '
- 'no\n'
- 'excess keyword arguments.\n'
- '\n'
- 'If the syntax "*expression" appears in the function call, '
- '"expression"\n'
- 'must evaluate to an *iterable*. Elements from these iterables are\n'
- 'treated as if they were additional positional arguments. For the '
- 'call\n'
- '"f(x1, x2, *y, x3, x4)", if *y* evaluates to a sequence *y1*, …, '
- '*yM*,\n'
- 'this is equivalent to a call with M+4 positional arguments *x1*, '
- '*x2*,\n'
- '*y1*, …, *yM*, *x3*, *x4*.\n'
- '\n'
- 'A consequence of this is that although the "*expression" syntax '
- 'may\n'
- 'appear *after* explicit keyword arguments, it is processed '
- '*before*\n'
- 'the keyword arguments (and any "**expression" arguments – see '
- 'below).\n'
- 'So:\n'
- '\n'
- ' >>> def f(a, b):\n'
- ' ... print(a, b)\n'
- ' ...\n'
- ' >>> f(b=1, *(2,))\n'
- ' 2 1\n'
- ' >>> f(a=1, *(2,))\n'
- ' Traceback (most recent call last):\n'
- ' File "<stdin>", line 1, in <module>\n'
- " TypeError: f() got multiple values for keyword argument 'a'\n"
- ' >>> f(1, *(2,))\n'
- ' 1 2\n'
- '\n'
- 'It is unusual for both keyword arguments and the "*expression" '
- 'syntax\n'
- 'to be used in the same call, so in practice this confusion does '
- 'not\n'
- 'often arise.\n'
- '\n'
- 'If the syntax "**expression" appears in the function call,\n'
- '"expression" must evaluate to a *mapping*, the contents of which '
- 'are\n'
- 'treated as additional keyword arguments. If a parameter matching a '
- 'key\n'
- 'has already been given a value (by an explicit keyword argument, '
- 'or\n'
- 'from another unpacking), a "TypeError" exception is raised.\n'
- '\n'
- 'When "**expression" is used, each key in this mapping must be a\n'
- 'string. Each value from the mapping is assigned to the first '
- 'formal\n'
- 'parameter eligible for keyword assignment whose name is equal to '
- 'the\n'
- 'key. A key need not be a Python identifier (e.g. ""max-temp °F"" '
- 'is\n'
- 'acceptable, although it will not match any formal parameter that '
- 'could\n'
- 'be declared). If there is no match to a formal parameter the '
- 'key-value\n'
- 'pair is collected by the "**" parameter, if there is one, or if '
- 'there\n'
- 'is not, a "TypeError" exception is raised.\n'
- '\n'
- 'Formal parameters using the syntax "*identifier" or "**identifier"\n'
- 'cannot be used as positional argument slots or as keyword argument\n'
- 'names.\n'
- '\n'
- 'Changed in version 3.5: Function calls accept any number of "*" '
- 'and\n'
- '"**" unpackings, positional arguments may follow iterable '
- 'unpackings\n'
- '("*"), and keyword arguments may follow dictionary unpackings '
- '("**").\n'
- 'Originally proposed by **PEP 448**.\n'
- '\n'
- 'A call always returns some value, possibly "None", unless it raises '
- 'an\n'
- 'exception. How this value is computed depends on the type of the\n'
- 'callable object.\n'
- '\n'
- 'If it is—\n'
- '\n'
- 'a user-defined function:\n'
- ' The code block for the function is executed, passing it the\n'
- ' argument list. The first thing the code block will do is bind '
- 'the\n'
- ' formal parameters to the arguments; this is described in '
- 'section\n'
- ' Function definitions. When the code block executes a "return"\n'
- ' statement, this specifies the return value of the function '
- 'call.\n'
- ' If execution reaches the end of the code block without executing '
- 'a\n'
- ' "return" statement, the return value is "None".\n'
- '\n'
- 'a built-in function or method:\n'
- ' The result is up to the interpreter; see Built-in Functions for '
- 'the\n'
- ' descriptions of built-in functions and methods.\n'
- '\n'
- 'a class object:\n'
- ' A new instance of that class is returned.\n'
- '\n'
- 'a class instance method:\n'
- ' The corresponding user-defined function is called, with an '
- 'argument\n'
- ' list that is one longer than the argument list of the call: the\n'
- ' instance becomes the first argument.\n'
- '\n'
- 'a class instance:\n'
- ' The class must define a "__call__()" method; the effect is then '
- 'the\n'
- ' same as if that method was called.\n',
- 'class': 'Class definitions\n'
- '*****************\n'
- '\n'
- 'A class definition defines a class object (see section The '
- 'standard\n'
- 'type hierarchy):\n'
- '\n'
- ' classdef ::= [decorators] "class" classname [type_params] '
- '[inheritance] ":" suite\n'
- ' inheritance ::= "(" [argument_list] ")"\n'
- ' classname ::= identifier\n'
- '\n'
- 'A class definition is an executable statement. The inheritance '
- 'list\n'
- 'usually gives a list of base classes (see Metaclasses for more\n'
- 'advanced uses), so each item in the list should evaluate to a '
- 'class\n'
- 'object which allows subclassing. Classes without an inheritance '
- 'list\n'
- 'inherit, by default, from the base class "object"; hence,\n'
- '\n'
- ' class Foo:\n'
- ' pass\n'
- '\n'
- 'is equivalent to\n'
- '\n'
- ' class Foo(object):\n'
- ' pass\n'
- '\n'
- 'The class’s suite is then executed in a new execution frame (see\n'
- 'Naming and binding), using a newly created local namespace and the\n'
- 'original global namespace. (Usually, the suite contains mostly\n'
- 'function definitions.) When the class’s suite finishes execution, '
- 'its\n'
- 'execution frame is discarded but its local namespace is saved. [5] '
- 'A\n'
- 'class object is then created using the inheritance list for the '
- 'base\n'
- 'classes and the saved local namespace for the attribute '
- 'dictionary.\n'
- 'The class name is bound to this class object in the original local\n'
- 'namespace.\n'
- '\n'
- 'The order in which attributes are defined in the class body is\n'
- 'preserved in the new class’s "__dict__". Note that this is '
- 'reliable\n'
- 'only right after the class is created and only for classes that '
- 'were\n'
- 'defined using the definition syntax.\n'
- '\n'
- 'Class creation can be customized heavily using metaclasses.\n'
- '\n'
- 'Classes can also be decorated: just like when decorating '
- 'functions,\n'
- '\n'
- ' @f1(arg)\n'
- ' @f2\n'
- ' class Foo: pass\n'
- '\n'
- 'is roughly equivalent to\n'
- '\n'
- ' class Foo: pass\n'
- ' Foo = f1(arg)(f2(Foo))\n'
- '\n'
- 'The evaluation rules for the decorator expressions are the same as '
- 'for\n'
- 'function decorators. The result is then bound to the class name.\n'
- '\n'
- 'Changed in version 3.9: Classes may be decorated with any valid\n'
- '"assignment_expression". Previously, the grammar was much more\n'
- 'restrictive; see **PEP 614** for details.\n'
- '\n'
- 'A list of type parameters may be given in square brackets '
- 'immediately\n'
- 'after the class’s name. This indicates to static type checkers '
- 'that\n'
- 'the class is generic. At runtime, the type parameters can be '
- 'retrieved\n'
- 'from the class’s "__type_params__" attribute. See Generic classes '
- 'for\n'
- 'more.\n'
- '\n'
- 'Changed in version 3.12: Type parameter lists are new in Python '
- '3.12.\n'
- '\n'
- '**Programmer’s note:** Variables defined in the class definition '
- 'are\n'
- 'class attributes; they are shared by instances. Instance '
- 'attributes\n'
- 'can be set in a method with "self.name = value". Both class and\n'
- 'instance attributes are accessible through the notation '
- '“"self.name"”,\n'
- 'and an instance attribute hides a class attribute with the same '
- 'name\n'
- 'when accessed in this way. Class attributes can be used as '
- 'defaults\n'
- 'for instance attributes, but using mutable values there can lead '
- 'to\n'
- 'unexpected results. Descriptors can be used to create instance\n'
- 'variables with different implementation details.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 3115** - Metaclasses in Python 3000\n'
- ' The proposal that changed the declaration of metaclasses to '
- 'the\n'
- ' current syntax, and the semantics for how classes with\n'
- ' metaclasses are constructed.\n'
- '\n'
- ' **PEP 3129** - Class Decorators\n'
- ' The proposal that added class decorators. Function and '
- 'method\n'
- ' decorators were introduced in **PEP 318**.\n',
- 'comparisons': 'Comparisons\n'
- '***********\n'
- '\n'
- 'Unlike C, all comparison operations in Python have the same '
- 'priority,\n'
- 'which is lower than that of any arithmetic, shifting or '
- 'bitwise\n'
- 'operation. Also unlike C, expressions like "a < b < c" have '
- 'the\n'
- 'interpretation that is conventional in mathematics:\n'
- '\n'
- ' comparison ::= or_expr (comp_operator or_expr)*\n'
- ' comp_operator ::= "<" | ">" | "==" | ">=" | "<=" | "!="\n'
- ' | "is" ["not"] | ["not"] "in"\n'
- '\n'
- 'Comparisons yield boolean values: "True" or "False". Custom '
- '*rich\n'
- 'comparison methods* may return non-boolean values. In this '
- 'case Python\n'
- 'will call "bool()" on such value in boolean contexts.\n'
- '\n'
- 'Comparisons can be chained arbitrarily, e.g., "x < y <= z" '
- 'is\n'
- 'equivalent to "x < y and y <= z", except that "y" is '
- 'evaluated only\n'
- 'once (but in both cases "z" is not evaluated at all when "x < '
- 'y" is\n'
- 'found to be false).\n'
- '\n'
- 'Formally, if *a*, *b*, *c*, …, *y*, *z* are expressions and '
- '*op1*,\n'
- '*op2*, …, *opN* are comparison operators, then "a op1 b op2 c '
- '... y\n'
- 'opN z" is equivalent to "a op1 b and b op2 c and ... y opN '
- 'z", except\n'
- 'that each expression is evaluated at most once.\n'
- '\n'
- 'Note that "a op1 b op2 c" doesn’t imply any kind of '
- 'comparison between\n'
- '*a* and *c*, so that, e.g., "x < y > z" is perfectly legal '
- '(though\n'
- 'perhaps not pretty).\n'
- '\n'
- '\n'
- 'Value comparisons\n'
- '=================\n'
- '\n'
- 'The operators "<", ">", "==", ">=", "<=", and "!=" compare '
- 'the values\n'
- 'of two objects. The objects do not need to have the same '
- 'type.\n'
- '\n'
- 'Chapter Objects, values and types states that objects have a '
- 'value (in\n'
- 'addition to type and identity). The value of an object is a '
- 'rather\n'
- 'abstract notion in Python: For example, there is no canonical '
- 'access\n'
- 'method for an object’s value. Also, there is no requirement '
- 'that the\n'
- 'value of an object should be constructed in a particular way, '
- 'e.g.\n'
- 'comprised of all its data attributes. Comparison operators '
- 'implement a\n'
- 'particular notion of what the value of an object is. One can '
- 'think of\n'
- 'them as defining the value of an object indirectly, by means '
- 'of their\n'
- 'comparison implementation.\n'
- '\n'
- 'Because all types are (direct or indirect) subtypes of '
- '"object", they\n'
- 'inherit the default comparison behavior from "object". Types '
- 'can\n'
- 'customize their comparison behavior by implementing *rich '
- 'comparison\n'
- 'methods* like "__lt__()", described in Basic customization.\n'
- '\n'
- 'The default behavior for equality comparison ("==" and "!=") '
- 'is based\n'
- 'on the identity of the objects. Hence, equality comparison '
- 'of\n'
- 'instances with the same identity results in equality, and '
- 'equality\n'
- 'comparison of instances with different identities results in\n'
- 'inequality. A motivation for this default behavior is the '
- 'desire that\n'
- 'all objects should be reflexive (i.e. "x is y" implies "x == '
- 'y").\n'
- '\n'
- 'A default order comparison ("<", ">", "<=", and ">=") is not '
- 'provided;\n'
- 'an attempt raises "TypeError". A motivation for this default '
- 'behavior\n'
- 'is the lack of a similar invariant as for equality.\n'
- '\n'
- 'The behavior of the default equality comparison, that '
- 'instances with\n'
- 'different identities are always unequal, may be in contrast '
- 'to what\n'
- 'types will need that have a sensible definition of object '
- 'value and\n'
- 'value-based equality. Such types will need to customize '
- 'their\n'
- 'comparison behavior, and in fact, a number of built-in types '
- 'have done\n'
- 'that.\n'
- '\n'
- 'The following list describes the comparison behavior of the '
- 'most\n'
- 'important built-in types.\n'
- '\n'
- '* Numbers of built-in numeric types (Numeric Types — int, '
- 'float,\n'
- ' complex) and of the standard library types '
- '"fractions.Fraction" and\n'
- ' "decimal.Decimal" can be compared within and across their '
- 'types,\n'
- ' with the restriction that complex numbers do not support '
- 'order\n'
- ' comparison. Within the limits of the types involved, they '
- 'compare\n'
- ' mathematically (algorithmically) correct without loss of '
- 'precision.\n'
- '\n'
- ' The not-a-number values "float(\'NaN\')" and '
- '"decimal.Decimal(\'NaN\')"\n'
- ' are special. Any ordered comparison of a number to a '
- 'not-a-number\n'
- ' value is false. A counter-intuitive implication is that '
- 'not-a-number\n'
- ' values are not equal to themselves. For example, if "x =\n'
- ' float(\'NaN\')", "3 < x", "x < 3" and "x == x" are all '
- 'false, while "x\n'
- ' != x" is true. This behavior is compliant with IEEE 754.\n'
- '\n'
- '* "None" and "NotImplemented" are singletons. **PEP 8** '
- 'advises that\n'
- ' comparisons for singletons should always be done with "is" '
- 'or "is\n'
- ' not", never the equality operators.\n'
- '\n'
- '* Binary sequences (instances of "bytes" or "bytearray") can '
- 'be\n'
- ' compared within and across their types. They compare\n'
- ' lexicographically using the numeric values of their '
- 'elements.\n'
- '\n'
- '* Strings (instances of "str") compare lexicographically '
- 'using the\n'
- ' numerical Unicode code points (the result of the built-in '
- 'function\n'
- ' "ord()") of their characters. [3]\n'
- '\n'
- ' Strings and binary sequences cannot be directly compared.\n'
- '\n'
- '* Sequences (instances of "tuple", "list", or "range") can be '
- 'compared\n'
- ' only within each of their types, with the restriction that '
- 'ranges do\n'
- ' not support order comparison. Equality comparison across '
- 'these\n'
- ' types results in inequality, and ordering comparison across '
- 'these\n'
- ' types raises "TypeError".\n'
- '\n'
- ' Sequences compare lexicographically using comparison of\n'
- ' corresponding elements. The built-in containers typically '
- 'assume\n'
- ' identical objects are equal to themselves. That lets them '
- 'bypass\n'
- ' equality tests for identical objects to improve performance '
- 'and to\n'
- ' maintain their internal invariants.\n'
- '\n'
- ' Lexicographical comparison between built-in collections '
- 'works as\n'
- ' follows:\n'
- '\n'
- ' * For two collections to compare equal, they must be of the '
- 'same\n'
- ' type, have the same length, and each pair of '
- 'corresponding\n'
- ' elements must compare equal (for example, "[1,2] == '
- '(1,2)" is\n'
- ' false because the type is not the same).\n'
- '\n'
- ' * Collections that support order comparison are ordered the '
- 'same as\n'
- ' their first unequal elements (for example, "[1,2,x] <= '
- '[1,2,y]"\n'
- ' has the same value as "x <= y"). If a corresponding '
- 'element does\n'
- ' not exist, the shorter collection is ordered first (for '
- 'example,\n'
- ' "[1,2] < [1,2,3]" is true).\n'
- '\n'
- '* Mappings (instances of "dict") compare equal if and only if '
- 'they\n'
- ' have equal "(key, value)" pairs. Equality comparison of the '
- 'keys and\n'
- ' values enforces reflexivity.\n'
- '\n'
- ' Order comparisons ("<", ">", "<=", and ">=") raise '
- '"TypeError".\n'
- '\n'
- '* Sets (instances of "set" or "frozenset") can be compared '
- 'within and\n'
- ' across their types.\n'
- '\n'
- ' They define order comparison operators to mean subset and '
- 'superset\n'
- ' tests. Those relations do not define total orderings (for '
- 'example,\n'
- ' the two sets "{1,2}" and "{2,3}" are not equal, nor subsets '
- 'of one\n'
- ' another, nor supersets of one another). Accordingly, sets '
- 'are not\n'
- ' appropriate arguments for functions which depend on total '
- 'ordering\n'
- ' (for example, "min()", "max()", and "sorted()" produce '
- 'undefined\n'
- ' results given a list of sets as inputs).\n'
- '\n'
- ' Comparison of sets enforces reflexivity of its elements.\n'
- '\n'
- '* Most other built-in types have no comparison methods '
- 'implemented, so\n'
- ' they inherit the default comparison behavior.\n'
- '\n'
- 'User-defined classes that customize their comparison behavior '
- 'should\n'
- 'follow some consistency rules, if possible:\n'
- '\n'
- '* Equality comparison should be reflexive. In other words, '
- 'identical\n'
- ' objects should compare equal:\n'
- '\n'
- ' "x is y" implies "x == y"\n'
- '\n'
- '* Comparison should be symmetric. In other words, the '
- 'following\n'
- ' expressions should have the same result:\n'
- '\n'
- ' "x == y" and "y == x"\n'
- '\n'
- ' "x != y" and "y != x"\n'
- '\n'
- ' "x < y" and "y > x"\n'
- '\n'
- ' "x <= y" and "y >= x"\n'
- '\n'
- '* Comparison should be transitive. The following '
- '(non-exhaustive)\n'
- ' examples illustrate that:\n'
- '\n'
- ' "x > y and y > z" implies "x > z"\n'
- '\n'
- ' "x < y and y <= z" implies "x < z"\n'
- '\n'
- '* Inverse comparison should result in the boolean negation. '
- 'In other\n'
- ' words, the following expressions should have the same '
- 'result:\n'
- '\n'
- ' "x == y" and "not x != y"\n'
- '\n'
- ' "x < y" and "not x >= y" (for total ordering)\n'
- '\n'
- ' "x > y" and "not x <= y" (for total ordering)\n'
- '\n'
- ' The last two expressions apply to totally ordered '
- 'collections (e.g.\n'
- ' to sequences, but not to sets or mappings). See also the\n'
- ' "total_ordering()" decorator.\n'
- '\n'
- '* The "hash()" result should be consistent with equality. '
- 'Objects that\n'
- ' are equal should either have the same hash value, or be '
- 'marked as\n'
- ' unhashable.\n'
- '\n'
- 'Python does not enforce these consistency rules. In fact, '
- 'the\n'
- 'not-a-number values are an example for not following these '
- 'rules.\n'
- '\n'
- '\n'
- 'Membership test operations\n'
- '==========================\n'
- '\n'
- 'The operators "in" and "not in" test for membership. "x in '
- 's"\n'
- 'evaluates to "True" if *x* is a member of *s*, and "False" '
- 'otherwise.\n'
- '"x not in s" returns the negation of "x in s". All built-in '
- 'sequences\n'
- 'and set types support this as well as dictionary, for which '
- '"in" tests\n'
- 'whether the dictionary has a given key. For container types '
- 'such as\n'
- 'list, tuple, set, frozenset, dict, or collections.deque, the\n'
- 'expression "x in y" is equivalent to "any(x is e or x == e '
- 'for e in\n'
- 'y)".\n'
- '\n'
- 'For the string and bytes types, "x in y" is "True" if and '
- 'only if *x*\n'
- 'is a substring of *y*. An equivalent test is "y.find(x) != '
- '-1".\n'
- 'Empty strings are always considered to be a substring of any '
- 'other\n'
- 'string, so """ in "abc"" will return "True".\n'
- '\n'
- 'For user-defined classes which define the "__contains__()" '
- 'method, "x\n'
- 'in y" returns "True" if "y.__contains__(x)" returns a true '
- 'value, and\n'
- '"False" otherwise.\n'
- '\n'
- 'For user-defined classes which do not define "__contains__()" '
- 'but do\n'
- 'define "__iter__()", "x in y" is "True" if some value "z", '
- 'for which\n'
- 'the expression "x is z or x == z" is true, is produced while '
- 'iterating\n'
- 'over "y". If an exception is raised during the iteration, it '
- 'is as if\n'
- '"in" raised that exception.\n'
- '\n'
- 'Lastly, the old-style iteration protocol is tried: if a class '
- 'defines\n'
- '"__getitem__()", "x in y" is "True" if and only if there is a '
- 'non-\n'
- 'negative integer index *i* such that "x is y[i] or x == '
- 'y[i]", and no\n'
- 'lower integer index raises the "IndexError" exception. (If '
- 'any other\n'
- 'exception is raised, it is as if "in" raised that '
- 'exception).\n'
- '\n'
- 'The operator "not in" is defined to have the inverse truth '
- 'value of\n'
- '"in".\n'
- '\n'
- '\n'
- 'Identity comparisons\n'
- '====================\n'
- '\n'
- 'The operators "is" and "is not" test for an object’s '
- 'identity: "x is\n'
- 'y" is true if and only if *x* and *y* are the same object. '
- 'An\n'
- 'Object’s identity is determined using the "id()" function. '
- '"x is not\n'
- 'y" yields the inverse truth value. [4]\n',
- 'compound': 'Compound statements\n'
- '*******************\n'
- '\n'
- 'Compound statements contain (groups of) other statements; they '
- 'affect\n'
- 'or control the execution of those other statements in some way. '
- 'In\n'
- 'general, compound statements span multiple lines, although in '
- 'simple\n'
- 'incarnations a whole compound statement may be contained in one '
- 'line.\n'
- '\n'
- 'The "if", "while" and "for" statements implement traditional '
- 'control\n'
- 'flow constructs. "try" specifies exception handlers and/or '
- 'cleanup\n'
- 'code for a group of statements, while the "with" statement '
- 'allows the\n'
- 'execution of initialization and finalization code around a block '
- 'of\n'
- 'code. Function and class definitions are also syntactically '
- 'compound\n'
- 'statements.\n'
- '\n'
- 'A compound statement consists of one or more ‘clauses.’ A '
- 'clause\n'
- 'consists of a header and a ‘suite.’ The clause headers of a\n'
- 'particular compound statement are all at the same indentation '
- 'level.\n'
- 'Each clause header begins with a uniquely identifying keyword '
- 'and ends\n'
- 'with a colon. A suite is a group of statements controlled by a\n'
- 'clause. A suite can be one or more semicolon-separated simple\n'
- 'statements on the same line as the header, following the '
- 'header’s\n'
- 'colon, or it can be one or more indented statements on '
- 'subsequent\n'
- 'lines. Only the latter form of a suite can contain nested '
- 'compound\n'
- 'statements; the following is illegal, mostly because it wouldn’t '
- 'be\n'
- 'clear to which "if" clause a following "else" clause would '
- 'belong:\n'
- '\n'
- ' if test1: if test2: print(x)\n'
- '\n'
- 'Also note that the semicolon binds tighter than the colon in '
- 'this\n'
- 'context, so that in the following example, either all or none of '
- 'the\n'
- '"print()" calls are executed:\n'
- '\n'
- ' if x < y < z: print(x); print(y); print(z)\n'
- '\n'
- 'Summarizing:\n'
- '\n'
- ' compound_stmt ::= if_stmt\n'
- ' | while_stmt\n'
- ' | for_stmt\n'
- ' | try_stmt\n'
- ' | with_stmt\n'
- ' | match_stmt\n'
- ' | funcdef\n'
- ' | classdef\n'
- ' | async_with_stmt\n'
- ' | async_for_stmt\n'
- ' | async_funcdef\n'
- ' suite ::= stmt_list NEWLINE | NEWLINE INDENT '
- 'statement+ DEDENT\n'
- ' statement ::= stmt_list NEWLINE | compound_stmt\n'
- ' stmt_list ::= simple_stmt (";" simple_stmt)* [";"]\n'
- '\n'
- 'Note that statements always end in a "NEWLINE" possibly followed '
- 'by a\n'
- '"DEDENT". Also note that optional continuation clauses always '
- 'begin\n'
- 'with a keyword that cannot start a statement, thus there are no\n'
- 'ambiguities (the ‘dangling "else"’ problem is solved in Python '
- 'by\n'
- 'requiring nested "if" statements to be indented).\n'
- '\n'
- 'The formatting of the grammar rules in the following sections '
- 'places\n'
- 'each clause on a separate line for clarity.\n'
- '\n'
- '\n'
- 'The "if" statement\n'
- '==================\n'
- '\n'
- 'The "if" statement is used for conditional execution:\n'
- '\n'
- ' if_stmt ::= "if" assignment_expression ":" suite\n'
- ' ("elif" assignment_expression ":" suite)*\n'
- ' ["else" ":" suite]\n'
- '\n'
- 'It selects exactly one of the suites by evaluating the '
- 'expressions one\n'
- 'by one until one is found to be true (see section Boolean '
- 'operations\n'
- 'for the definition of true and false); then that suite is '
- 'executed\n'
- '(and no other part of the "if" statement is executed or '
- 'evaluated).\n'
- 'If all expressions are false, the suite of the "else" clause, '
- 'if\n'
- 'present, is executed.\n'
- '\n'
- '\n'
- 'The "while" statement\n'
- '=====================\n'
- '\n'
- 'The "while" statement is used for repeated execution as long as '
- 'an\n'
- 'expression is true:\n'
- '\n'
- ' while_stmt ::= "while" assignment_expression ":" suite\n'
- ' ["else" ":" suite]\n'
- '\n'
- 'This repeatedly tests the expression and, if it is true, '
- 'executes the\n'
- 'first suite; if the expression is false (which may be the first '
- 'time\n'
- 'it is tested) the suite of the "else" clause, if present, is '
- 'executed\n'
- 'and the loop terminates.\n'
- '\n'
- 'A "break" statement executed in the first suite terminates the '
- 'loop\n'
- 'without executing the "else" clause’s suite. A "continue" '
- 'statement\n'
- 'executed in the first suite skips the rest of the suite and goes '
- 'back\n'
- 'to testing the expression.\n'
- '\n'
- '\n'
- 'The "for" statement\n'
- '===================\n'
- '\n'
- 'The "for" statement is used to iterate over the elements of a '
- 'sequence\n'
- '(such as a string, tuple or list) or other iterable object:\n'
- '\n'
- ' for_stmt ::= "for" target_list "in" starred_list ":" suite\n'
- ' ["else" ":" suite]\n'
- '\n'
- 'The "starred_list" expression is evaluated once; it should yield '
- 'an\n'
- '*iterable* object. An *iterator* is created for that iterable. '
- 'The\n'
- 'first item provided by the iterator is then assigned to the '
- 'target\n'
- 'list using the standard rules for assignments (see Assignment\n'
- 'statements), and the suite is executed. This repeats for each '
- 'item\n'
- 'provided by the iterator. When the iterator is exhausted, the '
- 'suite\n'
- 'in the "else" clause, if present, is executed, and the loop\n'
- 'terminates.\n'
- '\n'
- 'A "break" statement executed in the first suite terminates the '
- 'loop\n'
- 'without executing the "else" clause’s suite. A "continue" '
- 'statement\n'
- 'executed in the first suite skips the rest of the suite and '
- 'continues\n'
- 'with the next item, or with the "else" clause if there is no '
- 'next\n'
- 'item.\n'
- '\n'
- 'The for-loop makes assignments to the variables in the target '
- 'list.\n'
- 'This overwrites all previous assignments to those variables '
- 'including\n'
- 'those made in the suite of the for-loop:\n'
- '\n'
- ' for i in range(10):\n'
- ' print(i)\n'
- ' i = 5 # this will not affect the for-loop\n'
- ' # because i will be overwritten with '
- 'the next\n'
- ' # index in the range\n'
- '\n'
- 'Names in the target list are not deleted when the loop is '
- 'finished,\n'
- 'but if the sequence is empty, they will not have been assigned '
- 'to at\n'
- 'all by the loop. Hint: the built-in type "range()" represents\n'
- 'immutable arithmetic sequences of integers. For instance, '
- 'iterating\n'
- '"range(3)" successively yields 0, 1, and then 2.\n'
- '\n'
- 'Changed in version 3.11: Starred elements are now allowed in '
- 'the\n'
- 'expression list.\n'
- '\n'
- '\n'
- 'The "try" statement\n'
- '===================\n'
- '\n'
- 'The "try" statement specifies exception handlers and/or cleanup '
- 'code\n'
- 'for a group of statements:\n'
- '\n'
- ' try_stmt ::= try1_stmt | try2_stmt | try3_stmt\n'
- ' try1_stmt ::= "try" ":" suite\n'
- ' ("except" [expression ["as" identifier]] ":" '
- 'suite)+\n'
- ' ["else" ":" suite]\n'
- ' ["finally" ":" suite]\n'
- ' try2_stmt ::= "try" ":" suite\n'
- ' ("except" "*" expression ["as" identifier] ":" '
- 'suite)+\n'
- ' ["else" ":" suite]\n'
- ' ["finally" ":" suite]\n'
- ' try3_stmt ::= "try" ":" suite\n'
- ' "finally" ":" suite\n'
- '\n'
- 'Additional information on exceptions can be found in section\n'
- 'Exceptions, and information on using the "raise" statement to '
- 'generate\n'
- 'exceptions may be found in section The raise statement.\n'
- '\n'
- '\n'
- '"except" clause\n'
- '---------------\n'
- '\n'
- 'The "except" clause(s) specify one or more exception handlers. '
- 'When no\n'
- 'exception occurs in the "try" clause, no exception handler is\n'
- 'executed. When an exception occurs in the "try" suite, a search '
- 'for an\n'
- 'exception handler is started. This search inspects the "except"\n'
- 'clauses in turn until one is found that matches the exception. '
- 'An\n'
- 'expression-less "except" clause, if present, must be last; it '
- 'matches\n'
- 'any exception.\n'
- '\n'
- 'For an "except" clause with an expression, the expression must\n'
- 'evaluate to an exception type or a tuple of exception types. '
- 'The\n'
- 'raised exception matches an "except" clause whose expression '
- 'evaluates\n'
- 'to the class or a *non-virtual base class* of the exception '
- 'object, or\n'
- 'to a tuple that contains such a class.\n'
- '\n'
- 'If no "except" clause matches the exception, the search for an\n'
- 'exception handler continues in the surrounding code and on the\n'
- 'invocation stack. [1]\n'
- '\n'
- 'If the evaluation of an expression in the header of an "except" '
- 'clause\n'
- 'raises an exception, the original search for a handler is '
- 'canceled and\n'
- 'a search starts for the new exception in the surrounding code '
- 'and on\n'
- 'the call stack (it is treated as if the entire "try" statement '
- 'raised\n'
- 'the exception).\n'
- '\n'
- 'When a matching "except" clause is found, the exception is '
- 'assigned to\n'
- 'the target specified after the "as" keyword in that "except" '
- 'clause,\n'
- 'if present, and the "except" clause’s suite is executed. All '
- '"except"\n'
- 'clauses must have an executable block. When the end of this '
- 'block is\n'
- 'reached, execution continues normally after the entire "try"\n'
- 'statement. (This means that if two nested handlers exist for the '
- 'same\n'
- 'exception, and the exception occurs in the "try" clause of the '
- 'inner\n'
- 'handler, the outer handler will not handle the exception.)\n'
- '\n'
- 'When an exception has been assigned using "as target", it is '
- 'cleared\n'
- 'at the end of the "except" clause. This is as if\n'
- '\n'
- ' except E as N:\n'
- ' foo\n'
- '\n'
- 'was translated to\n'
- '\n'
- ' except E as N:\n'
- ' try:\n'
- ' foo\n'
- ' finally:\n'
- ' del N\n'
- '\n'
- 'This means the exception must be assigned to a different name to '
- 'be\n'
- 'able to refer to it after the "except" clause. Exceptions are '
- 'cleared\n'
- 'because with the traceback attached to them, they form a '
- 'reference\n'
- 'cycle with the stack frame, keeping all locals in that frame '
- 'alive\n'
- 'until the next garbage collection occurs.\n'
- '\n'
- 'Before an "except" clause’s suite is executed, the exception is '
- 'stored\n'
- 'in the "sys" module, where it can be accessed from within the '
- 'body of\n'
- 'the "except" clause by calling "sys.exception()". When leaving '
- 'an\n'
- 'exception handler, the exception stored in the "sys" module is '
- 'reset\n'
- 'to its previous value:\n'
- '\n'
- ' >>> print(sys.exception())\n'
- ' None\n'
- ' >>> try:\n'
- ' ... raise TypeError\n'
- ' ... except:\n'
- ' ... print(repr(sys.exception()))\n'
- ' ... try:\n'
- ' ... raise ValueError\n'
- ' ... except:\n'
- ' ... print(repr(sys.exception()))\n'
- ' ... print(repr(sys.exception()))\n'
- ' ...\n'
- ' TypeError()\n'
- ' ValueError()\n'
- ' TypeError()\n'
- ' >>> print(sys.exception())\n'
- ' None\n'
- '\n'
- '\n'
- '"except*" clause\n'
- '----------------\n'
- '\n'
- 'The "except*" clause(s) are used for handling "ExceptionGroup"s. '
- 'The\n'
- 'exception type for matching is interpreted as in the case of '
- '"except",\n'
- 'but in the case of exception groups we can have partial matches '
- 'when\n'
- 'the type matches some of the exceptions in the group. This means '
- 'that\n'
- 'multiple "except*" clauses can execute, each handling part of '
- 'the\n'
- 'exception group. Each clause executes at most once and handles '
- 'an\n'
- 'exception group of all matching exceptions. Each exception in '
- 'the\n'
- 'group is handled by at most one "except*" clause, the first '
- 'that\n'
- 'matches it.\n'
- '\n'
- ' >>> try:\n'
- ' ... raise ExceptionGroup("eg",\n'
- ' ... [ValueError(1), TypeError(2), OSError(3), '
- 'OSError(4)])\n'
- ' ... except* TypeError as e:\n'
- " ... print(f'caught {type(e)} with nested "
- "{e.exceptions}')\n"
- ' ... except* OSError as e:\n'
- " ... print(f'caught {type(e)} with nested "
- "{e.exceptions}')\n"
- ' ...\n'
- " caught <class 'ExceptionGroup'> with nested (TypeError(2),)\n"
- " caught <class 'ExceptionGroup'> with nested (OSError(3), "
- 'OSError(4))\n'
- ' + Exception Group Traceback (most recent call last):\n'
- ' | File "<stdin>", line 2, in <module>\n'
- ' | ExceptionGroup: eg\n'
- ' +-+---------------- 1 ----------------\n'
- ' | ValueError: 1\n'
- ' +------------------------------------\n'
- '\n'
- 'Any remaining exceptions that were not handled by any "except*" '
- 'clause\n'
- 'are re-raised at the end, along with all exceptions that were '
- 'raised\n'
- 'from within the "except*" clauses. If this list contains more '
- 'than one\n'
- 'exception to reraise, they are combined into an exception '
- 'group.\n'
- '\n'
- 'If the raised exception is not an exception group and its type '
- 'matches\n'
- 'one of the "except*" clauses, it is caught and wrapped by an '
- 'exception\n'
- 'group with an empty message string.\n'
- '\n'
- ' >>> try:\n'
- ' ... raise BlockingIOError\n'
- ' ... except* BlockingIOError as e:\n'
- ' ... print(repr(e))\n'
- ' ...\n'
- " ExceptionGroup('', (BlockingIOError()))\n"
- '\n'
- 'An "except*" clause must have a matching expression; it cannot '
- 'be\n'
- '"except*:". Furthermore, this expression cannot contain '
- 'exception\n'
- 'group types, because that would have ambiguous semantics.\n'
- '\n'
- 'It is not possible to mix "except" and "except*" in the same '
- '"try".\n'
- '"break", "continue" and "return" cannot appear in an "except*" '
- 'clause.\n'
- '\n'
- '\n'
- '"else" clause\n'
- '-------------\n'
- '\n'
- 'The optional "else" clause is executed if the control flow '
- 'leaves the\n'
- '"try" suite, no exception was raised, and no "return", '
- '"continue", or\n'
- '"break" statement was executed. Exceptions in the "else" clause '
- 'are\n'
- 'not handled by the preceding "except" clauses.\n'
- '\n'
- '\n'
- '"finally" clause\n'
- '----------------\n'
- '\n'
- 'If "finally" is present, it specifies a ‘cleanup’ handler. The '
- '"try"\n'
- 'clause is executed, including any "except" and "else" clauses. '
- 'If an\n'
- 'exception occurs in any of the clauses and is not handled, the\n'
- 'exception is temporarily saved. The "finally" clause is '
- 'executed. If\n'
- 'there is a saved exception it is re-raised at the end of the '
- '"finally"\n'
- 'clause. If the "finally" clause raises another exception, the '
- 'saved\n'
- 'exception is set as the context of the new exception. If the '
- '"finally"\n'
- 'clause executes a "return", "break" or "continue" statement, the '
- 'saved\n'
- 'exception is discarded:\n'
- '\n'
- ' >>> def f():\n'
- ' ... try:\n'
- ' ... 1/0\n'
- ' ... finally:\n'
- ' ... return 42\n'
- ' ...\n'
- ' >>> f()\n'
- ' 42\n'
- '\n'
- 'The exception information is not available to the program '
- 'during\n'
- 'execution of the "finally" clause.\n'
- '\n'
- 'When a "return", "break" or "continue" statement is executed in '
- 'the\n'
- '"try" suite of a "try"…"finally" statement, the "finally" clause '
- 'is\n'
- 'also executed ‘on the way out.’\n'
- '\n'
- 'The return value of a function is determined by the last '
- '"return"\n'
- 'statement executed. Since the "finally" clause always executes, '
- 'a\n'
- '"return" statement executed in the "finally" clause will always '
- 'be the\n'
- 'last one executed:\n'
- '\n'
- ' >>> def foo():\n'
- ' ... try:\n'
- " ... return 'try'\n"
- ' ... finally:\n'
- " ... return 'finally'\n"
- ' ...\n'
- ' >>> foo()\n'
- " 'finally'\n"
- '\n'
- 'Changed in version 3.8: Prior to Python 3.8, a "continue" '
- 'statement\n'
- 'was illegal in the "finally" clause due to a problem with the\n'
- 'implementation.\n'
- '\n'
- '\n'
- 'The "with" statement\n'
- '====================\n'
- '\n'
- 'The "with" statement is used to wrap the execution of a block '
- 'with\n'
- 'methods defined by a context manager (see section With '
- 'Statement\n'
- 'Context Managers). This allows common "try"…"except"…"finally" '
- 'usage\n'
- 'patterns to be encapsulated for convenient reuse.\n'
- '\n'
- ' with_stmt ::= "with" ( "(" with_stmt_contents ","? '
- '")" | with_stmt_contents ) ":" suite\n'
- ' with_stmt_contents ::= with_item ("," with_item)*\n'
- ' with_item ::= expression ["as" target]\n'
- '\n'
- 'The execution of the "with" statement with one “item” proceeds '
- 'as\n'
- 'follows:\n'
- '\n'
- '1. The context expression (the expression given in the '
- '"with_item") is\n'
- ' evaluated to obtain a context manager.\n'
- '\n'
- '2. The context manager’s "__enter__()" is loaded for later use.\n'
- '\n'
- '3. The context manager’s "__exit__()" is loaded for later use.\n'
- '\n'
- '4. The context manager’s "__enter__()" method is invoked.\n'
- '\n'
- '5. If a target was included in the "with" statement, the return '
- 'value\n'
- ' from "__enter__()" is assigned to it.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' The "with" statement guarantees that if the "__enter__()" '
- 'method\n'
- ' returns without an error, then "__exit__()" will always be\n'
- ' called. Thus, if an error occurs during the assignment to '
- 'the\n'
- ' target list, it will be treated the same as an error '
- 'occurring\n'
- ' within the suite would be. See step 7 below.\n'
- '\n'
- '6. The suite is executed.\n'
- '\n'
- '7. The context manager’s "__exit__()" method is invoked. If an\n'
- ' exception caused the suite to be exited, its type, value, '
- 'and\n'
- ' traceback are passed as arguments to "__exit__()". Otherwise, '
- 'three\n'
- ' "None" arguments are supplied.\n'
- '\n'
- ' If the suite was exited due to an exception, and the return '
- 'value\n'
- ' from the "__exit__()" method was false, the exception is '
- 'reraised.\n'
- ' If the return value was true, the exception is suppressed, '
- 'and\n'
- ' execution continues with the statement following the "with"\n'
- ' statement.\n'
- '\n'
- ' If the suite was exited for any reason other than an '
- 'exception, the\n'
- ' return value from "__exit__()" is ignored, and execution '
- 'proceeds\n'
- ' at the normal location for the kind of exit that was taken.\n'
- '\n'
- 'The following code:\n'
- '\n'
- ' with EXPRESSION as TARGET:\n'
- ' SUITE\n'
- '\n'
- 'is semantically equivalent to:\n'
- '\n'
- ' manager = (EXPRESSION)\n'
- ' enter = type(manager).__enter__\n'
- ' exit = type(manager).__exit__\n'
- ' value = enter(manager)\n'
- ' hit_except = False\n'
- '\n'
- ' try:\n'
- ' TARGET = value\n'
- ' SUITE\n'
- ' except:\n'
- ' hit_except = True\n'
- ' if not exit(manager, *sys.exc_info()):\n'
- ' raise\n'
- ' finally:\n'
- ' if not hit_except:\n'
- ' exit(manager, None, None, None)\n'
- '\n'
- 'With more than one item, the context managers are processed as '
- 'if\n'
- 'multiple "with" statements were nested:\n'
- '\n'
- ' with A() as a, B() as b:\n'
- ' SUITE\n'
- '\n'
- 'is semantically equivalent to:\n'
- '\n'
- ' with A() as a:\n'
- ' with B() as b:\n'
- ' SUITE\n'
- '\n'
- 'You can also write multi-item context managers in multiple lines '
- 'if\n'
- 'the items are surrounded by parentheses. For example:\n'
- '\n'
- ' with (\n'
- ' A() as a,\n'
- ' B() as b,\n'
- ' ):\n'
- ' SUITE\n'
- '\n'
- 'Changed in version 3.1: Support for multiple context '
- 'expressions.\n'
- '\n'
- 'Changed in version 3.10: Support for using grouping parentheses '
- 'to\n'
- 'break the statement in multiple lines.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 343** - The “with” statement\n'
- ' The specification, background, and examples for the Python '
- '"with"\n'
- ' statement.\n'
- '\n'
- '\n'
- 'The "match" statement\n'
- '=====================\n'
- '\n'
- 'Added in version 3.10.\n'
- '\n'
- 'The match statement is used for pattern matching. Syntax:\n'
- '\n'
- ' match_stmt ::= \'match\' subject_expr ":" NEWLINE INDENT '
- 'case_block+ DEDENT\n'
- ' subject_expr ::= star_named_expression "," '
- 'star_named_expressions?\n'
- ' | named_expression\n'
- ' case_block ::= \'case\' patterns [guard] ":" block\n'
- '\n'
- 'Note:\n'
- '\n'
- ' This section uses single quotes to denote soft keywords.\n'
- '\n'
- 'Pattern matching takes a pattern as input (following "case") and '
- 'a\n'
- 'subject value (following "match"). The pattern (which may '
- 'contain\n'
- 'subpatterns) is matched against the subject value. The outcomes '
- 'are:\n'
- '\n'
- '* A match success or failure (also termed a pattern success or\n'
- ' failure).\n'
- '\n'
- '* Possible binding of matched values to a name. The '
- 'prerequisites for\n'
- ' this are further discussed below.\n'
- '\n'
- 'The "match" and "case" keywords are soft keywords.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' * **PEP 634** – Structural Pattern Matching: Specification\n'
- '\n'
- ' * **PEP 636** – Structural Pattern Matching: Tutorial\n'
- '\n'
- '\n'
- 'Overview\n'
- '--------\n'
- '\n'
- 'Here’s an overview of the logical flow of a match statement:\n'
- '\n'
- '1. The subject expression "subject_expr" is evaluated and a '
- 'resulting\n'
- ' subject value obtained. If the subject expression contains a '
- 'comma,\n'
- ' a tuple is constructed using the standard rules.\n'
- '\n'
- '2. Each pattern in a "case_block" is attempted to match with '
- 'the\n'
- ' subject value. The specific rules for success or failure are\n'
- ' described below. The match attempt can also bind some or all '
- 'of the\n'
- ' standalone names within the pattern. The precise pattern '
- 'binding\n'
- ' rules vary per pattern type and are specified below. **Name\n'
- ' bindings made during a successful pattern match outlive the\n'
- ' executed block and can be used after the match statement**.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' During failed pattern matches, some subpatterns may '
- 'succeed. Do\n'
- ' not rely on bindings being made for a failed match. '
- 'Conversely,\n'
- ' do not rely on variables remaining unchanged after a '
- 'failed\n'
- ' match. The exact behavior is dependent on implementation '
- 'and may\n'
- ' vary. This is an intentional decision made to allow '
- 'different\n'
- ' implementations to add optimizations.\n'
- '\n'
- '3. If the pattern succeeds, the corresponding guard (if present) '
- 'is\n'
- ' evaluated. In this case all name bindings are guaranteed to '
- 'have\n'
- ' happened.\n'
- '\n'
- ' * If the guard evaluates as true or is missing, the "block" '
- 'inside\n'
- ' "case_block" is executed.\n'
- '\n'
- ' * Otherwise, the next "case_block" is attempted as described '
- 'above.\n'
- '\n'
- ' * If there are no further case blocks, the match statement '
- 'is\n'
- ' completed.\n'
- '\n'
- 'Note:\n'
- '\n'
- ' Users should generally never rely on a pattern being '
- 'evaluated.\n'
- ' Depending on implementation, the interpreter may cache values '
- 'or use\n'
- ' other optimizations which skip repeated evaluations.\n'
- '\n'
- 'A sample match statement:\n'
- '\n'
- ' >>> flag = False\n'
- ' >>> match (100, 200):\n'
- ' ... case (100, 300): # Mismatch: 200 != 300\n'
- " ... print('Case 1')\n"
- ' ... case (100, 200) if flag: # Successful match, but '
- 'guard fails\n'
- " ... print('Case 2')\n"
- ' ... case (100, y): # Matches and binds y to 200\n'
- " ... print(f'Case 3, y: {y}')\n"
- ' ... case _: # Pattern not attempted\n'
- " ... print('Case 4, I match anything!')\n"
- ' ...\n'
- ' Case 3, y: 200\n'
- '\n'
- 'In this case, "if flag" is a guard. Read more about that in the '
- 'next\n'
- 'section.\n'
- '\n'
- '\n'
- 'Guards\n'
- '------\n'
- '\n'
- ' guard ::= "if" named_expression\n'
- '\n'
- 'A "guard" (which is part of the "case") must succeed for code '
- 'inside\n'
- 'the "case" block to execute. It takes the form: "if" followed '
- 'by an\n'
- 'expression.\n'
- '\n'
- 'The logical flow of a "case" block with a "guard" follows:\n'
- '\n'
- '1. Check that the pattern in the "case" block succeeded. If '
- 'the\n'
- ' pattern failed, the "guard" is not evaluated and the next '
- '"case"\n'
- ' block is checked.\n'
- '\n'
- '2. If the pattern succeeded, evaluate the "guard".\n'
- '\n'
- ' * If the "guard" condition evaluates as true, the case block '
- 'is\n'
- ' selected.\n'
- '\n'
- ' * If the "guard" condition evaluates as false, the case block '
- 'is\n'
- ' not selected.\n'
- '\n'
- ' * If the "guard" raises an exception during evaluation, the\n'
- ' exception bubbles up.\n'
- '\n'
- 'Guards are allowed to have side effects as they are '
- 'expressions.\n'
- 'Guard evaluation must proceed from the first to the last case '
- 'block,\n'
- 'one at a time, skipping case blocks whose pattern(s) don’t all\n'
- 'succeed. (I.e., guard evaluation must happen in order.) Guard\n'
- 'evaluation must stop once a case block is selected.\n'
- '\n'
- '\n'
- 'Irrefutable Case Blocks\n'
- '-----------------------\n'
- '\n'
- 'An irrefutable case block is a match-all case block. A match\n'
- 'statement may have at most one irrefutable case block, and it '
- 'must be\n'
- 'last.\n'
- '\n'
- 'A case block is considered irrefutable if it has no guard and '
- 'its\n'
- 'pattern is irrefutable. A pattern is considered irrefutable if '
- 'we can\n'
- 'prove from its syntax alone that it will always succeed. Only '
- 'the\n'
- 'following patterns are irrefutable:\n'
- '\n'
- '* AS Patterns whose left-hand side is irrefutable\n'
- '\n'
- '* OR Patterns containing at least one irrefutable pattern\n'
- '\n'
- '* Capture Patterns\n'
- '\n'
- '* Wildcard Patterns\n'
- '\n'
- '* parenthesized irrefutable patterns\n'
- '\n'
- '\n'
- 'Patterns\n'
- '--------\n'
- '\n'
- 'Note:\n'
- '\n'
- ' This section uses grammar notations beyond standard EBNF:\n'
- '\n'
- ' * the notation "SEP.RULE+" is shorthand for "RULE (SEP '
- 'RULE)*"\n'
- '\n'
- ' * the notation "!RULE" is shorthand for a negative lookahead\n'
- ' assertion\n'
- '\n'
- 'The top-level syntax for "patterns" is:\n'
- '\n'
- ' patterns ::= open_sequence_pattern | pattern\n'
- ' pattern ::= as_pattern | or_pattern\n'
- ' closed_pattern ::= | literal_pattern\n'
- ' | capture_pattern\n'
- ' | wildcard_pattern\n'
- ' | value_pattern\n'
- ' | group_pattern\n'
- ' | sequence_pattern\n'
- ' | mapping_pattern\n'
- ' | class_pattern\n'
- '\n'
- 'The descriptions below will include a description “in simple '
- 'terms” of\n'
- 'what a pattern does for illustration purposes (credits to '
- 'Raymond\n'
- 'Hettinger for a document that inspired most of the '
- 'descriptions). Note\n'
- 'that these descriptions are purely for illustration purposes and '
- '**may\n'
- 'not** reflect the underlying implementation. Furthermore, they '
- 'do not\n'
- 'cover all valid forms.\n'
- '\n'
- '\n'
- 'OR Patterns\n'
- '~~~~~~~~~~~\n'
- '\n'
- 'An OR pattern is two or more patterns separated by vertical bars '
- '"|".\n'
- 'Syntax:\n'
- '\n'
- ' or_pattern ::= "|".closed_pattern+\n'
- '\n'
- 'Only the final subpattern may be irrefutable, and each '
- 'subpattern must\n'
- 'bind the same set of names to avoid ambiguity.\n'
- '\n'
- 'An OR pattern matches each of its subpatterns in turn to the '
- 'subject\n'
- 'value, until one succeeds. The OR pattern is then considered\n'
- 'successful. Otherwise, if none of the subpatterns succeed, the '
- 'OR\n'
- 'pattern fails.\n'
- '\n'
- 'In simple terms, "P1 | P2 | ..." will try to match "P1", if it '
- 'fails\n'
- 'it will try to match "P2", succeeding immediately if any '
- 'succeeds,\n'
- 'failing otherwise.\n'
- '\n'
- '\n'
- 'AS Patterns\n'
- '~~~~~~~~~~~\n'
- '\n'
- 'An AS pattern matches an OR pattern on the left of the "as" '
- 'keyword\n'
- 'against a subject. Syntax:\n'
- '\n'
- ' as_pattern ::= or_pattern "as" capture_pattern\n'
- '\n'
- 'If the OR pattern fails, the AS pattern fails. Otherwise, the '
- 'AS\n'
- 'pattern binds the subject to the name on the right of the as '
- 'keyword\n'
- 'and succeeds. "capture_pattern" cannot be a "_".\n'
- '\n'
- 'In simple terms "P as NAME" will match with "P", and on success '
- 'it\n'
- 'will set "NAME = <subject>".\n'
- '\n'
- '\n'
- 'Literal Patterns\n'
- '~~~~~~~~~~~~~~~~\n'
- '\n'
- 'A literal pattern corresponds to most literals in Python. '
- 'Syntax:\n'
- '\n'
- ' literal_pattern ::= signed_number\n'
- ' | signed_number "+" NUMBER\n'
- ' | signed_number "-" NUMBER\n'
- ' | strings\n'
- ' | "None"\n'
- ' | "True"\n'
- ' | "False"\n'
- ' signed_number ::= ["-"] NUMBER\n'
- '\n'
- 'The rule "strings" and the token "NUMBER" are defined in the '
- 'standard\n'
- 'Python grammar. Triple-quoted strings are supported. Raw '
- 'strings and\n'
- 'byte strings are supported. f-strings are not supported.\n'
- '\n'
- 'The forms "signed_number \'+\' NUMBER" and "signed_number \'-\' '
- 'NUMBER"\n'
- 'are for expressing complex numbers; they require a real number '
- 'on the\n'
- 'left and an imaginary number on the right. E.g. "3 + 4j".\n'
- '\n'
- 'In simple terms, "LITERAL" will succeed only if "<subject> ==\n'
- 'LITERAL". For the singletons "None", "True" and "False", the '
- '"is"\n'
- 'operator is used.\n'
- '\n'
- '\n'
- 'Capture Patterns\n'
- '~~~~~~~~~~~~~~~~\n'
- '\n'
- 'A capture pattern binds the subject value to a name. Syntax:\n'
- '\n'
- " capture_pattern ::= !'_' NAME\n"
- '\n'
- 'A single underscore "_" is not a capture pattern (this is what '
- '"!\'_\'"\n'
- 'expresses). It is instead treated as a "wildcard_pattern".\n'
- '\n'
- 'In a given pattern, a given name can only be bound once. E.g. '
- '"case\n'
- 'x, x: ..." is invalid while "case [x] | x: ..." is allowed.\n'
- '\n'
- 'Capture patterns always succeed. The binding follows scoping '
- 'rules\n'
- 'established by the assignment expression operator in **PEP '
- '572**; the\n'
- 'name becomes a local variable in the closest containing function '
- 'scope\n'
- 'unless there’s an applicable "global" or "nonlocal" statement.\n'
- '\n'
- 'In simple terms "NAME" will always succeed and it will set "NAME '
- '=\n'
- '<subject>".\n'
- '\n'
- '\n'
- 'Wildcard Patterns\n'
- '~~~~~~~~~~~~~~~~~\n'
- '\n'
- 'A wildcard pattern always succeeds (matches anything) and binds '
- 'no\n'
- 'name. Syntax:\n'
- '\n'
- " wildcard_pattern ::= '_'\n"
- '\n'
- '"_" is a soft keyword within any pattern, but only within '
- 'patterns.\n'
- 'It is an identifier, as usual, even within "match" subject\n'
- 'expressions, "guard"s, and "case" blocks.\n'
- '\n'
- 'In simple terms, "_" will always succeed.\n'
- '\n'
- '\n'
- 'Value Patterns\n'
- '~~~~~~~~~~~~~~\n'
- '\n'
- 'A value pattern represents a named value in Python. Syntax:\n'
- '\n'
- ' value_pattern ::= attr\n'
- ' attr ::= name_or_attr "." NAME\n'
- ' name_or_attr ::= attr | NAME\n'
- '\n'
- 'The dotted name in the pattern is looked up using standard '
- 'Python name\n'
- 'resolution rules. The pattern succeeds if the value found '
- 'compares\n'
- 'equal to the subject value (using the "==" equality operator).\n'
- '\n'
- 'In simple terms "NAME1.NAME2" will succeed only if "<subject> '
- '==\n'
- 'NAME1.NAME2"\n'
- '\n'
- 'Note:\n'
- '\n'
- ' If the same value occurs multiple times in the same match '
- 'statement,\n'
- ' the interpreter may cache the first value found and reuse it '
- 'rather\n'
- ' than repeat the same lookup. This cache is strictly tied to a '
- 'given\n'
- ' execution of a given match statement.\n'
- '\n'
- '\n'
- 'Group Patterns\n'
- '~~~~~~~~~~~~~~\n'
- '\n'
- 'A group pattern allows users to add parentheses around patterns '
- 'to\n'
- 'emphasize the intended grouping. Otherwise, it has no '
- 'additional\n'
- 'syntax. Syntax:\n'
- '\n'
- ' group_pattern ::= "(" pattern ")"\n'
- '\n'
- 'In simple terms "(P)" has the same effect as "P".\n'
- '\n'
- '\n'
- 'Sequence Patterns\n'
- '~~~~~~~~~~~~~~~~~\n'
- '\n'
- 'A sequence pattern contains several subpatterns to be matched '
- 'against\n'
- 'sequence elements. The syntax is similar to the unpacking of a '
- 'list or\n'
- 'tuple.\n'
- '\n'
- ' sequence_pattern ::= "[" [maybe_sequence_pattern] "]"\n'
- ' | "(" [open_sequence_pattern] ")"\n'
- ' open_sequence_pattern ::= maybe_star_pattern "," '
- '[maybe_sequence_pattern]\n'
- ' maybe_sequence_pattern ::= ",".maybe_star_pattern+ ","?\n'
- ' maybe_star_pattern ::= star_pattern | pattern\n'
- ' star_pattern ::= "*" (capture_pattern | '
- 'wildcard_pattern)\n'
- '\n'
- 'There is no difference if parentheses or square brackets are '
- 'used for\n'
- 'sequence patterns (i.e. "(...)" vs "[...]" ).\n'
- '\n'
- 'Note:\n'
- '\n'
- ' A single pattern enclosed in parentheses without a trailing '
- 'comma\n'
- ' (e.g. "(3 | 4)") is a group pattern. While a single pattern '
- 'enclosed\n'
- ' in square brackets (e.g. "[3 | 4]") is still a sequence '
- 'pattern.\n'
- '\n'
- 'At most one star subpattern may be in a sequence pattern. The '
- 'star\n'
- 'subpattern may occur in any position. If no star subpattern is\n'
- 'present, the sequence pattern is a fixed-length sequence '
- 'pattern;\n'
- 'otherwise it is a variable-length sequence pattern.\n'
- '\n'
- 'The following is the logical flow for matching a sequence '
- 'pattern\n'
- 'against a subject value:\n'
- '\n'
- '1. If the subject value is not a sequence [2], the sequence '
- 'pattern\n'
- ' fails.\n'
- '\n'
- '2. If the subject value is an instance of "str", "bytes" or\n'
- ' "bytearray" the sequence pattern fails.\n'
- '\n'
- '3. The subsequent steps depend on whether the sequence pattern '
- 'is\n'
- ' fixed or variable-length.\n'
- '\n'
- ' If the sequence pattern is fixed-length:\n'
- '\n'
- ' 1. If the length of the subject sequence is not equal to the '
- 'number\n'
- ' of subpatterns, the sequence pattern fails\n'
- '\n'
- ' 2. Subpatterns in the sequence pattern are matched to their\n'
- ' corresponding items in the subject sequence from left to '
- 'right.\n'
- ' Matching stops as soon as a subpattern fails. If all\n'
- ' subpatterns succeed in matching their corresponding item, '
- 'the\n'
- ' sequence pattern succeeds.\n'
- '\n'
- ' Otherwise, if the sequence pattern is variable-length:\n'
- '\n'
- ' 1. If the length of the subject sequence is less than the '
- 'number of\n'
- ' non-star subpatterns, the sequence pattern fails.\n'
- '\n'
- ' 2. The leading non-star subpatterns are matched to their\n'
- ' corresponding items as for fixed-length sequences.\n'
- '\n'
- ' 3. If the previous step succeeds, the star subpattern matches '
- 'a\n'
- ' list formed of the remaining subject items, excluding the\n'
- ' remaining items corresponding to non-star subpatterns '
- 'following\n'
- ' the star subpattern.\n'
- '\n'
- ' 4. Remaining non-star subpatterns are matched to their\n'
- ' corresponding subject items, as for a fixed-length '
- 'sequence.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' The length of the subject sequence is obtained via "len()" '
- '(i.e.\n'
- ' via the "__len__()" protocol). This length may be cached '
- 'by the\n'
- ' interpreter in a similar manner as value patterns.\n'
- '\n'
- 'In simple terms "[P1, P2, P3," … ", P<N>]" matches only if all '
- 'the\n'
- 'following happens:\n'
- '\n'
- '* check "<subject>" is a sequence\n'
- '\n'
- '* "len(subject) == <N>"\n'
- '\n'
- '* "P1" matches "<subject>[0]" (note that this match can also '
- 'bind\n'
- ' names)\n'
- '\n'
- '* "P2" matches "<subject>[1]" (note that this match can also '
- 'bind\n'
- ' names)\n'
- '\n'
- '* … and so on for the corresponding pattern/element.\n'
- '\n'
- '\n'
- 'Mapping Patterns\n'
- '~~~~~~~~~~~~~~~~\n'
- '\n'
- 'A mapping pattern contains one or more key-value patterns. The '
- 'syntax\n'
- 'is similar to the construction of a dictionary. Syntax:\n'
- '\n'
- ' mapping_pattern ::= "{" [items_pattern] "}"\n'
- ' items_pattern ::= ",".key_value_pattern+ ","?\n'
- ' key_value_pattern ::= (literal_pattern | value_pattern) ":" '
- 'pattern\n'
- ' | double_star_pattern\n'
- ' double_star_pattern ::= "**" capture_pattern\n'
- '\n'
- 'At most one double star pattern may be in a mapping pattern. '
- 'The\n'
- 'double star pattern must be the last subpattern in the mapping\n'
- 'pattern.\n'
- '\n'
- 'Duplicate keys in mapping patterns are disallowed. Duplicate '
- 'literal\n'
- 'keys will raise a "SyntaxError". Two keys that otherwise have '
- 'the same\n'
- 'value will raise a "ValueError" at runtime.\n'
- '\n'
- 'The following is the logical flow for matching a mapping '
- 'pattern\n'
- 'against a subject value:\n'
- '\n'
- '1. If the subject value is not a mapping [3],the mapping '
- 'pattern\n'
- ' fails.\n'
- '\n'
- '2. If every key given in the mapping pattern is present in the '
- 'subject\n'
- ' mapping, and the pattern for each key matches the '
- 'corresponding\n'
- ' item of the subject mapping, the mapping pattern succeeds.\n'
- '\n'
- '3. If duplicate keys are detected in the mapping pattern, the '
- 'pattern\n'
- ' is considered invalid. A "SyntaxError" is raised for '
- 'duplicate\n'
- ' literal values; or a "ValueError" for named keys of the same '
- 'value.\n'
- '\n'
- 'Note:\n'
- '\n'
- ' Key-value pairs are matched using the two-argument form of '
- 'the\n'
- ' mapping subject’s "get()" method. Matched key-value pairs '
- 'must\n'
- ' already be present in the mapping, and not created on-the-fly '
- 'via\n'
- ' "__missing__()" or "__getitem__()".\n'
- '\n'
- 'In simple terms "{KEY1: P1, KEY2: P2, ... }" matches only if all '
- 'the\n'
- 'following happens:\n'
- '\n'
- '* check "<subject>" is a mapping\n'
- '\n'
- '* "KEY1 in <subject>"\n'
- '\n'
- '* "P1" matches "<subject>[KEY1]"\n'
- '\n'
- '* … and so on for the corresponding KEY/pattern pair.\n'
- '\n'
- '\n'
- 'Class Patterns\n'
- '~~~~~~~~~~~~~~\n'
- '\n'
- 'A class pattern represents a class and its positional and '
- 'keyword\n'
- 'arguments (if any). Syntax:\n'
- '\n'
- ' class_pattern ::= name_or_attr "(" [pattern_arguments '
- '","?] ")"\n'
- ' pattern_arguments ::= positional_patterns ["," '
- 'keyword_patterns]\n'
- ' | keyword_patterns\n'
- ' positional_patterns ::= ",".pattern+\n'
- ' keyword_patterns ::= ",".keyword_pattern+\n'
- ' keyword_pattern ::= NAME "=" pattern\n'
- '\n'
- 'The same keyword should not be repeated in class patterns.\n'
- '\n'
- 'The following is the logical flow for matching a class pattern '
- 'against\n'
- 'a subject value:\n'
- '\n'
- '1. If "name_or_attr" is not an instance of the builtin "type" , '
- 'raise\n'
- ' "TypeError".\n'
- '\n'
- '2. If the subject value is not an instance of "name_or_attr" '
- '(tested\n'
- ' via "isinstance()"), the class pattern fails.\n'
- '\n'
- '3. If no pattern arguments are present, the pattern succeeds.\n'
- ' Otherwise, the subsequent steps depend on whether keyword or\n'
- ' positional argument patterns are present.\n'
- '\n'
- ' For a number of built-in types (specified below), a single\n'
- ' positional subpattern is accepted which will match the '
- 'entire\n'
- ' subject; for these types keyword patterns also work as for '
- 'other\n'
- ' types.\n'
- '\n'
- ' If only keyword patterns are present, they are processed as\n'
- ' follows, one by one:\n'
- '\n'
- ' I. The keyword is looked up as an attribute on the subject.\n'
- '\n'
- ' * If this raises an exception other than "AttributeError", '
- 'the\n'
- ' exception bubbles up.\n'
- '\n'
- ' * If this raises "AttributeError", the class pattern has '
- 'failed.\n'
- '\n'
- ' * Else, the subpattern associated with the keyword pattern '
- 'is\n'
- ' matched against the subject’s attribute value. If this '
- 'fails,\n'
- ' the class pattern fails; if this succeeds, the match '
- 'proceeds\n'
- ' to the next keyword.\n'
- '\n'
- ' II. If all keyword patterns succeed, the class pattern '
- 'succeeds.\n'
- '\n'
- ' If any positional patterns are present, they are converted '
- 'to\n'
- ' keyword patterns using the "__match_args__" attribute on the '
- 'class\n'
- ' "name_or_attr" before matching:\n'
- '\n'
- ' I. The equivalent of "getattr(cls, "__match_args__", ())" is\n'
- ' called.\n'
- '\n'
- ' * If this raises an exception, the exception bubbles up.\n'
- '\n'
- ' * If the returned value is not a tuple, the conversion '
- 'fails and\n'
- ' "TypeError" is raised.\n'
- '\n'
- ' * If there are more positional patterns than\n'
- ' "len(cls.__match_args__)", "TypeError" is raised.\n'
- '\n'
- ' * Otherwise, positional pattern "i" is converted to a '
- 'keyword\n'
- ' pattern using "__match_args__[i]" as the keyword.\n'
- ' "__match_args__[i]" must be a string; if not "TypeError" '
- 'is\n'
- ' raised.\n'
- '\n'
- ' * If there are duplicate keywords, "TypeError" is raised.\n'
- '\n'
- ' See also:\n'
- '\n'
- ' Customizing positional arguments in class pattern '
- 'matching\n'
- '\n'
- ' II. Once all positional patterns have been converted to '
- 'keyword\n'
- ' patterns,\n'
- ' the match proceeds as if there were only keyword '
- 'patterns.\n'
- '\n'
- ' For the following built-in types the handling of positional\n'
- ' subpatterns is different:\n'
- '\n'
- ' * "bool"\n'
- '\n'
- ' * "bytearray"\n'
- '\n'
- ' * "bytes"\n'
- '\n'
- ' * "dict"\n'
- '\n'
- ' * "float"\n'
- '\n'
- ' * "frozenset"\n'
- '\n'
- ' * "int"\n'
- '\n'
- ' * "list"\n'
- '\n'
- ' * "set"\n'
- '\n'
- ' * "str"\n'
- '\n'
- ' * "tuple"\n'
- '\n'
- ' These classes accept a single positional argument, and the '
- 'pattern\n'
- ' there is matched against the whole object rather than an '
- 'attribute.\n'
- ' For example "int(0|1)" matches the value "0", but not the '
- 'value\n'
- ' "0.0".\n'
- '\n'
- 'In simple terms "CLS(P1, attr=P2)" matches only if the '
- 'following\n'
- 'happens:\n'
- '\n'
- '* "isinstance(<subject>, CLS)"\n'
- '\n'
- '* convert "P1" to a keyword pattern using "CLS.__match_args__"\n'
- '\n'
- '* For each keyword argument "attr=P2":\n'
- '\n'
- ' * "hasattr(<subject>, "attr")"\n'
- '\n'
- ' * "P2" matches "<subject>.attr"\n'
- '\n'
- '* … and so on for the corresponding keyword argument/pattern '
- 'pair.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' * **PEP 634** – Structural Pattern Matching: Specification\n'
- '\n'
- ' * **PEP 636** – Structural Pattern Matching: Tutorial\n'
- '\n'
- '\n'
- 'Function definitions\n'
- '====================\n'
- '\n'
- 'A function definition defines a user-defined function object '
- '(see\n'
- 'section The standard type hierarchy):\n'
- '\n'
- ' funcdef ::= [decorators] "def" funcname '
- '[type_params] "(" [parameter_list] ")"\n'
- ' ["->" expression] ":" suite\n'
- ' decorators ::= decorator+\n'
- ' decorator ::= "@" assignment_expression '
- 'NEWLINE\n'
- ' parameter_list ::= defparameter ("," '
- 'defparameter)* "," "/" ["," [parameter_list_no_posonly]]\n'
- ' | parameter_list_no_posonly\n'
- ' parameter_list_no_posonly ::= defparameter ("," '
- 'defparameter)* ["," [parameter_list_starargs]]\n'
- ' | parameter_list_starargs\n'
- ' parameter_list_starargs ::= "*" [star_parameter] ("," '
- 'defparameter)* ["," [parameter_star_kwargs]]\n'
- ' "*" ("," defparameter)+ ["," '
- '[parameter_star_kwargs]]\n'
- ' | parameter_star_kwargs\n'
- ' parameter_star_kwargs ::= "**" parameter [","]\n'
- ' parameter ::= identifier [":" expression]\n'
- ' star_parameter ::= identifier [":" ["*"] '
- 'expression]\n'
- ' defparameter ::= parameter ["=" expression]\n'
- ' funcname ::= identifier\n'
- '\n'
- 'A function definition is an executable statement. Its execution '
- 'binds\n'
- 'the function name in the current local namespace to a function '
- 'object\n'
- '(a wrapper around the executable code for the function). This\n'
- 'function object contains a reference to the current global '
- 'namespace\n'
- 'as the global namespace to be used when the function is called.\n'
- '\n'
- 'The function definition does not execute the function body; this '
- 'gets\n'
- 'executed only when the function is called. [4]\n'
- '\n'
- 'A function definition may be wrapped by one or more *decorator*\n'
- 'expressions. Decorator expressions are evaluated when the '
- 'function is\n'
- 'defined, in the scope that contains the function definition. '
- 'The\n'
- 'result must be a callable, which is invoked with the function '
- 'object\n'
- 'as the only argument. The returned value is bound to the '
- 'function name\n'
- 'instead of the function object. Multiple decorators are applied '
- 'in\n'
- 'nested fashion. For example, the following code\n'
- '\n'
- ' @f1(arg)\n'
- ' @f2\n'
- ' def func(): pass\n'
- '\n'
- 'is roughly equivalent to\n'
- '\n'
- ' def func(): pass\n'
- ' func = f1(arg)(f2(func))\n'
- '\n'
- 'except that the original function is not temporarily bound to '
- 'the name\n'
- '"func".\n'
- '\n'
- 'Changed in version 3.9: Functions may be decorated with any '
- 'valid\n'
- '"assignment_expression". Previously, the grammar was much more\n'
- 'restrictive; see **PEP 614** for details.\n'
- '\n'
- 'A list of type parameters may be given in square brackets '
- 'between the\n'
- 'function’s name and the opening parenthesis for its parameter '
- 'list.\n'
- 'This indicates to static type checkers that the function is '
- 'generic.\n'
- 'At runtime, the type parameters can be retrieved from the '
- 'function’s\n'
- '"__type_params__" attribute. See Generic functions for more.\n'
- '\n'
- 'Changed in version 3.12: Type parameter lists are new in Python '
- '3.12.\n'
- '\n'
- 'When one or more *parameters* have the form *parameter* "="\n'
- '*expression*, the function is said to have “default parameter '
- 'values.”\n'
- 'For a parameter with a default value, the corresponding '
- '*argument* may\n'
- 'be omitted from a call, in which case the parameter’s default '
- 'value is\n'
- 'substituted. If a parameter has a default value, all following\n'
- 'parameters up until the “"*"” must also have a default value — '
- 'this is\n'
- 'a syntactic restriction that is not expressed by the grammar.\n'
- '\n'
- '**Default parameter values are evaluated from left to right when '
- 'the\n'
- 'function definition is executed.** This means that the '
- 'expression is\n'
- 'evaluated once, when the function is defined, and that the same '
- '“pre-\n'
- 'computed” value is used for each call. This is especially '
- 'important\n'
- 'to understand when a default parameter value is a mutable '
- 'object, such\n'
- 'as a list or a dictionary: if the function modifies the object '
- '(e.g.\n'
- 'by appending an item to a list), the default parameter value is '
- 'in\n'
- 'effect modified. This is generally not what was intended. A '
- 'way\n'
- 'around this is to use "None" as the default, and explicitly test '
- 'for\n'
- 'it in the body of the function, e.g.:\n'
- '\n'
- ' def whats_on_the_telly(penguin=None):\n'
- ' if penguin is None:\n'
- ' penguin = []\n'
- ' penguin.append("property of the zoo")\n'
- ' return penguin\n'
- '\n'
- 'Function call semantics are described in more detail in section '
- 'Calls.\n'
- 'A function call always assigns values to all parameters '
- 'mentioned in\n'
- 'the parameter list, either from positional arguments, from '
- 'keyword\n'
- 'arguments, or from default values. If the form “"*identifier"” '
- 'is\n'
- 'present, it is initialized to a tuple receiving any excess '
- 'positional\n'
- 'parameters, defaulting to the empty tuple. If the form\n'
- '“"**identifier"” is present, it is initialized to a new ordered\n'
- 'mapping receiving any excess keyword arguments, defaulting to a '
- 'new\n'
- 'empty mapping of the same type. Parameters after “"*"” or\n'
- '“"*identifier"” are keyword-only parameters and may only be '
- 'passed by\n'
- 'keyword arguments. Parameters before “"/"” are positional-only\n'
- 'parameters and may only be passed by positional arguments.\n'
- '\n'
- 'Changed in version 3.8: The "/" function parameter syntax may be '
- 'used\n'
- 'to indicate positional-only parameters. See **PEP 570** for '
- 'details.\n'
- '\n'
- 'Parameters may have an *annotation* of the form “": '
- 'expression"”\n'
- 'following the parameter name. Any parameter may have an '
- 'annotation,\n'
- 'even those of the form "*identifier" or "**identifier". (As a '
- 'special\n'
- 'case, parameters of the form "*identifier" may have an '
- 'annotation “":\n'
- '*expression"”.) Functions may have “return” annotation of the '
- 'form\n'
- '“"-> expression"” after the parameter list. These annotations '
- 'can be\n'
- 'any valid Python expression. The presence of annotations does '
- 'not\n'
- 'change the semantics of a function. The annotation values are\n'
- 'available as values of a dictionary keyed by the parameters’ '
- 'names in\n'
- 'the "__annotations__" attribute of the function object. If the\n'
- '"annotations" import from "__future__" is used, annotations are\n'
- 'preserved as strings at runtime which enables postponed '
- 'evaluation.\n'
- 'Otherwise, they are evaluated when the function definition is\n'
- 'executed. In this case annotations may be evaluated in a '
- 'different\n'
- 'order than they appear in the source code.\n'
- '\n'
- 'Changed in version 3.11: Parameters of the form “"*identifier"” '
- 'may\n'
- 'have an annotation “": *expression"”. See **PEP 646**.\n'
- '\n'
- 'It is also possible to create anonymous functions (functions not '
- 'bound\n'
- 'to a name), for immediate use in expressions. This uses lambda\n'
- 'expressions, described in section Lambdas. Note that the '
- 'lambda\n'
- 'expression is merely a shorthand for a simplified function '
- 'definition;\n'
- 'a function defined in a “"def"” statement can be passed around '
- 'or\n'
- 'assigned to another name just like a function defined by a '
- 'lambda\n'
- 'expression. The “"def"” form is actually more powerful since '
- 'it\n'
- 'allows the execution of multiple statements and annotations.\n'
- '\n'
- '**Programmer’s note:** Functions are first-class objects. A '
- '“"def"”\n'
- 'statement executed inside a function definition defines a local\n'
- 'function that can be returned or passed around. Free variables '
- 'used\n'
- 'in the nested function can access the local variables of the '
- 'function\n'
- 'containing the def. See section Naming and binding for '
- 'details.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 3107** - Function Annotations\n'
- ' The original specification for function annotations.\n'
- '\n'
- ' **PEP 484** - Type Hints\n'
- ' Definition of a standard meaning for annotations: type '
- 'hints.\n'
- '\n'
- ' **PEP 526** - Syntax for Variable Annotations\n'
- ' Ability to type hint variable declarations, including '
- 'class\n'
- ' variables and instance variables.\n'
- '\n'
- ' **PEP 563** - Postponed Evaluation of Annotations\n'
- ' Support for forward references within annotations by '
- 'preserving\n'
- ' annotations in a string form at runtime instead of eager\n'
- ' evaluation.\n'
- '\n'
- ' **PEP 318** - Decorators for Functions and Methods\n'
- ' Function and method decorators were introduced. Class '
- 'decorators\n'
- ' were introduced in **PEP 3129**.\n'
- '\n'
- '\n'
- 'Class definitions\n'
- '=================\n'
- '\n'
- 'A class definition defines a class object (see section The '
- 'standard\n'
- 'type hierarchy):\n'
- '\n'
- ' classdef ::= [decorators] "class" classname [type_params] '
- '[inheritance] ":" suite\n'
- ' inheritance ::= "(" [argument_list] ")"\n'
- ' classname ::= identifier\n'
- '\n'
- 'A class definition is an executable statement. The inheritance '
- 'list\n'
- 'usually gives a list of base classes (see Metaclasses for more\n'
- 'advanced uses), so each item in the list should evaluate to a '
- 'class\n'
- 'object which allows subclassing. Classes without an inheritance '
- 'list\n'
- 'inherit, by default, from the base class "object"; hence,\n'
- '\n'
- ' class Foo:\n'
- ' pass\n'
- '\n'
- 'is equivalent to\n'
- '\n'
- ' class Foo(object):\n'
- ' pass\n'
- '\n'
- 'The class’s suite is then executed in a new execution frame '
- '(see\n'
- 'Naming and binding), using a newly created local namespace and '
- 'the\n'
- 'original global namespace. (Usually, the suite contains mostly\n'
- 'function definitions.) When the class’s suite finishes '
- 'execution, its\n'
- 'execution frame is discarded but its local namespace is saved. '
- '[5] A\n'
- 'class object is then created using the inheritance list for the '
- 'base\n'
- 'classes and the saved local namespace for the attribute '
- 'dictionary.\n'
- 'The class name is bound to this class object in the original '
- 'local\n'
- 'namespace.\n'
- '\n'
- 'The order in which attributes are defined in the class body is\n'
- 'preserved in the new class’s "__dict__". Note that this is '
- 'reliable\n'
- 'only right after the class is created and only for classes that '
- 'were\n'
- 'defined using the definition syntax.\n'
- '\n'
- 'Class creation can be customized heavily using metaclasses.\n'
- '\n'
- 'Classes can also be decorated: just like when decorating '
- 'functions,\n'
- '\n'
- ' @f1(arg)\n'
- ' @f2\n'
- ' class Foo: pass\n'
- '\n'
- 'is roughly equivalent to\n'
- '\n'
- ' class Foo: pass\n'
- ' Foo = f1(arg)(f2(Foo))\n'
- '\n'
- 'The evaluation rules for the decorator expressions are the same '
- 'as for\n'
- 'function decorators. The result is then bound to the class '
- 'name.\n'
- '\n'
- 'Changed in version 3.9: Classes may be decorated with any valid\n'
- '"assignment_expression". Previously, the grammar was much more\n'
- 'restrictive; see **PEP 614** for details.\n'
- '\n'
- 'A list of type parameters may be given in square brackets '
- 'immediately\n'
- 'after the class’s name. This indicates to static type checkers '
- 'that\n'
- 'the class is generic. At runtime, the type parameters can be '
- 'retrieved\n'
- 'from the class’s "__type_params__" attribute. See Generic '
- 'classes for\n'
- 'more.\n'
- '\n'
- 'Changed in version 3.12: Type parameter lists are new in Python '
- '3.12.\n'
- '\n'
- '**Programmer’s note:** Variables defined in the class definition '
- 'are\n'
- 'class attributes; they are shared by instances. Instance '
- 'attributes\n'
- 'can be set in a method with "self.name = value". Both class '
- 'and\n'
- 'instance attributes are accessible through the notation '
- '“"self.name"”,\n'
- 'and an instance attribute hides a class attribute with the same '
- 'name\n'
- 'when accessed in this way. Class attributes can be used as '
- 'defaults\n'
- 'for instance attributes, but using mutable values there can lead '
- 'to\n'
- 'unexpected results. Descriptors can be used to create instance\n'
- 'variables with different implementation details.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 3115** - Metaclasses in Python 3000\n'
- ' The proposal that changed the declaration of metaclasses to '
- 'the\n'
- ' current syntax, and the semantics for how classes with\n'
- ' metaclasses are constructed.\n'
- '\n'
- ' **PEP 3129** - Class Decorators\n'
- ' The proposal that added class decorators. Function and '
- 'method\n'
- ' decorators were introduced in **PEP 318**.\n'
- '\n'
- '\n'
- 'Coroutines\n'
- '==========\n'
- '\n'
- 'Added in version 3.5.\n'
- '\n'
- '\n'
- 'Coroutine function definition\n'
- '-----------------------------\n'
- '\n'
- ' async_funcdef ::= [decorators] "async" "def" funcname "(" '
- '[parameter_list] ")"\n'
- ' ["->" expression] ":" suite\n'
- '\n'
- 'Execution of Python coroutines can be suspended and resumed at '
- 'many\n'
- 'points (see *coroutine*). "await" expressions, "async for" and '
- '"async\n'
- 'with" can only be used in the body of a coroutine function.\n'
- '\n'
- 'Functions defined with "async def" syntax are always coroutine\n'
- 'functions, even if they do not contain "await" or "async" '
- 'keywords.\n'
- '\n'
- 'It is a "SyntaxError" to use a "yield from" expression inside '
- 'the body\n'
- 'of a coroutine function.\n'
- '\n'
- 'An example of a coroutine function:\n'
- '\n'
- ' async def func(param1, param2):\n'
- ' do_stuff()\n'
- ' await some_coroutine()\n'
- '\n'
- 'Changed in version 3.7: "await" and "async" are now keywords;\n'
- 'previously they were only treated as such inside the body of a\n'
- 'coroutine function.\n'
- '\n'
- '\n'
- 'The "async for" statement\n'
- '-------------------------\n'
- '\n'
- ' async_for_stmt ::= "async" for_stmt\n'
- '\n'
- 'An *asynchronous iterable* provides an "__aiter__" method that\n'
- 'directly returns an *asynchronous iterator*, which can call\n'
- 'asynchronous code in its "__anext__" method.\n'
- '\n'
- 'The "async for" statement allows convenient iteration over\n'
- 'asynchronous iterables.\n'
- '\n'
- 'The following code:\n'
- '\n'
- ' async for TARGET in ITER:\n'
- ' SUITE\n'
- ' else:\n'
- ' SUITE2\n'
- '\n'
- 'Is semantically equivalent to:\n'
- '\n'
- ' iter = (ITER)\n'
- ' iter = type(iter).__aiter__(iter)\n'
- ' running = True\n'
- '\n'
- ' while running:\n'
- ' try:\n'
- ' TARGET = await type(iter).__anext__(iter)\n'
- ' except StopAsyncIteration:\n'
- ' running = False\n'
- ' else:\n'
- ' SUITE\n'
- ' else:\n'
- ' SUITE2\n'
- '\n'
- 'See also "__aiter__()" and "__anext__()" for details.\n'
- '\n'
- 'It is a "SyntaxError" to use an "async for" statement outside '
- 'the body\n'
- 'of a coroutine function.\n'
- '\n'
- '\n'
- 'The "async with" statement\n'
- '--------------------------\n'
- '\n'
- ' async_with_stmt ::= "async" with_stmt\n'
- '\n'
- 'An *asynchronous context manager* is a *context manager* that is '
- 'able\n'
- 'to suspend execution in its *enter* and *exit* methods.\n'
- '\n'
- 'The following code:\n'
- '\n'
- ' async with EXPRESSION as TARGET:\n'
- ' SUITE\n'
- '\n'
- 'is semantically equivalent to:\n'
- '\n'
- ' manager = (EXPRESSION)\n'
- ' aenter = type(manager).__aenter__\n'
- ' aexit = type(manager).__aexit__\n'
- ' value = await aenter(manager)\n'
- ' hit_except = False\n'
- '\n'
- ' try:\n'
- ' TARGET = value\n'
- ' SUITE\n'
- ' except:\n'
- ' hit_except = True\n'
- ' if not await aexit(manager, *sys.exc_info()):\n'
- ' raise\n'
- ' finally:\n'
- ' if not hit_except:\n'
- ' await aexit(manager, None, None, None)\n'
- '\n'
- 'See also "__aenter__()" and "__aexit__()" for details.\n'
- '\n'
- 'It is a "SyntaxError" to use an "async with" statement outside '
- 'the\n'
- 'body of a coroutine function.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 492** - Coroutines with async and await syntax\n'
- ' The proposal that made coroutines a proper standalone '
- 'concept in\n'
- ' Python, and added supporting syntax.\n'
- '\n'
- '\n'
- 'Type parameter lists\n'
- '====================\n'
- '\n'
- 'Added in version 3.12.\n'
- '\n'
- ' type_params ::= "[" type_param ("," type_param)* "]"\n'
- ' type_param ::= typevar | typevartuple | paramspec\n'
- ' typevar ::= identifier (":" expression)?\n'
- ' typevartuple ::= "*" identifier\n'
- ' paramspec ::= "**" identifier\n'
- '\n'
- 'Functions (including coroutines), classes and type aliases may '
- 'contain\n'
- 'a type parameter list:\n'
- '\n'
- ' def max[T](args: list[T]) -> T:\n'
- ' ...\n'
- '\n'
- ' async def amax[T](args: list[T]) -> T:\n'
- ' ...\n'
- '\n'
- ' class Bag[T]:\n'
- ' def __iter__(self) -> Iterator[T]:\n'
- ' ...\n'
- '\n'
- ' def add(self, arg: T) -> None:\n'
- ' ...\n'
- '\n'
- ' type ListOrSet[T] = list[T] | set[T]\n'
- '\n'
- 'Semantically, this indicates that the function, class, or type '
- 'alias\n'
- 'is generic over a type variable. This information is primarily '
- 'used by\n'
- 'static type checkers, and at runtime, generic objects behave '
- 'much like\n'
- 'their non-generic counterparts.\n'
- '\n'
- 'Type parameters are declared in square brackets ("[]") '
- 'immediately\n'
- 'after the name of the function, class, or type alias. The type\n'
- 'parameters are accessible within the scope of the generic '
- 'object, but\n'
- 'not elsewhere. Thus, after a declaration "def func[T](): pass", '
- 'the\n'
- 'name "T" is not available in the module scope. Below, the '
- 'semantics of\n'
- 'generic objects are described with more precision. The scope of '
- 'type\n'
- 'parameters is modeled with a special function (technically, an\n'
- 'annotation scope) that wraps the creation of the generic '
- 'object.\n'
- '\n'
- 'Generic functions, classes, and type aliases have a '
- '"__type_params__"\n'
- 'attribute listing their type parameters.\n'
- '\n'
- 'Type parameters come in three kinds:\n'
- '\n'
- '* "typing.TypeVar", introduced by a plain name (e.g., "T").\n'
- ' Semantically, this represents a single type to a type '
- 'checker.\n'
- '\n'
- '* "typing.TypeVarTuple", introduced by a name prefixed with a '
- 'single\n'
- ' asterisk (e.g., "*Ts"). Semantically, this stands for a tuple '
- 'of any\n'
- ' number of types.\n'
- '\n'
- '* "typing.ParamSpec", introduced by a name prefixed with two '
- 'asterisks\n'
- ' (e.g., "**P"). Semantically, this stands for the parameters of '
- 'a\n'
- ' callable.\n'
- '\n'
- '"typing.TypeVar" declarations can define *bounds* and '
- '*constraints*\n'
- 'with a colon (":") followed by an expression. A single '
- 'expression\n'
- 'after the colon indicates a bound (e.g. "T: int"). Semantically, '
- 'this\n'
- 'means that the "typing.TypeVar" can only represent types that '
- 'are a\n'
- 'subtype of this bound. A parenthesized tuple of expressions '
- 'after the\n'
- 'colon indicates a set of constraints (e.g. "T: (str, bytes)"). '
- 'Each\n'
- 'member of the tuple should be a type (again, this is not '
- 'enforced at\n'
- 'runtime). Constrained type variables can only take on one of the '
- 'types\n'
- 'in the list of constraints.\n'
- '\n'
- 'For "typing.TypeVar"s declared using the type parameter list '
- 'syntax,\n'
- 'the bound and constraints are not evaluated when the generic '
- 'object is\n'
- 'created, but only when the value is explicitly accessed through '
- 'the\n'
- 'attributes "__bound__" and "__constraints__". To accomplish '
- 'this, the\n'
- 'bounds or constraints are evaluated in a separate annotation '
- 'scope.\n'
- '\n'
- '"typing.TypeVarTuple"s and "typing.ParamSpec"s cannot have '
- 'bounds or\n'
- 'constraints.\n'
- '\n'
- 'The following example indicates the full set of allowed type '
- 'parameter\n'
- 'declarations:\n'
- '\n'
- ' def overly_generic[\n'
- ' SimpleTypeVar,\n'
- ' TypeVarWithBound: int,\n'
- ' TypeVarWithConstraints: (str, bytes),\n'
- ' *SimpleTypeVarTuple,\n'
- ' **SimpleParamSpec,\n'
- ' ](\n'
- ' a: SimpleTypeVar,\n'
- ' b: TypeVarWithBound,\n'
- ' c: Callable[SimpleParamSpec, TypeVarWithConstraints],\n'
- ' *d: SimpleTypeVarTuple,\n'
- ' ): ...\n'
- '\n'
- '\n'
- 'Generic functions\n'
- '-----------------\n'
- '\n'
- 'Generic functions are declared as follows:\n'
- '\n'
- ' def func[T](arg: T): ...\n'
- '\n'
- 'This syntax is equivalent to:\n'
- '\n'
- ' annotation-def TYPE_PARAMS_OF_func():\n'
- ' T = typing.TypeVar("T")\n'
- ' def func(arg: T): ...\n'
- ' func.__type_params__ = (T,)\n'
- ' return func\n'
- ' func = TYPE_PARAMS_OF_func()\n'
- '\n'
- 'Here "annotation-def" indicates an annotation scope, which is '
- 'not\n'
- 'actually bound to any name at runtime. (One other liberty is '
- 'taken in\n'
- 'the translation: the syntax does not go through attribute access '
- 'on\n'
- 'the "typing" module, but creates an instance of '
- '"typing.TypeVar"\n'
- 'directly.)\n'
- '\n'
- 'The annotations of generic functions are evaluated within the\n'
- 'annotation scope used for declaring the type parameters, but '
- 'the\n'
- 'function’s defaults and decorators are not.\n'
- '\n'
- 'The following example illustrates the scoping rules for these '
- 'cases,\n'
- 'as well as for additional flavors of type parameters:\n'
- '\n'
- ' @decorator\n'
- ' def func[T: int, *Ts, **P](*args: *Ts, arg: Callable[P, T] = '
- 'some_default):\n'
- ' ...\n'
- '\n'
- 'Except for the lazy evaluation of the "TypeVar" bound, this is\n'
- 'equivalent to:\n'
- '\n'
- ' DEFAULT_OF_arg = some_default\n'
- '\n'
- ' annotation-def TYPE_PARAMS_OF_func():\n'
- '\n'
- ' annotation-def BOUND_OF_T():\n'
- ' return int\n'
- ' # In reality, BOUND_OF_T() is evaluated only on demand.\n'
- ' T = typing.TypeVar("T", bound=BOUND_OF_T())\n'
- '\n'
- ' Ts = typing.TypeVarTuple("Ts")\n'
- ' P = typing.ParamSpec("P")\n'
- '\n'
- ' def func(*args: *Ts, arg: Callable[P, T] = '
- 'DEFAULT_OF_arg):\n'
- ' ...\n'
- '\n'
- ' func.__type_params__ = (T, Ts, P)\n'
- ' return func\n'
- ' func = decorator(TYPE_PARAMS_OF_func())\n'
- '\n'
- 'The capitalized names like "DEFAULT_OF_arg" are not actually '
- 'bound at\n'
- 'runtime.\n'
- '\n'
- '\n'
- 'Generic classes\n'
- '---------------\n'
- '\n'
- 'Generic classes are declared as follows:\n'
- '\n'
- ' class Bag[T]: ...\n'
- '\n'
- 'This syntax is equivalent to:\n'
- '\n'
- ' annotation-def TYPE_PARAMS_OF_Bag():\n'
- ' T = typing.TypeVar("T")\n'
- ' class Bag(typing.Generic[T]):\n'
- ' __type_params__ = (T,)\n'
- ' ...\n'
- ' return Bag\n'
- ' Bag = TYPE_PARAMS_OF_Bag()\n'
- '\n'
- 'Here again "annotation-def" (not a real keyword) indicates an\n'
- 'annotation scope, and the name "TYPE_PARAMS_OF_Bag" is not '
- 'actually\n'
- 'bound at runtime.\n'
- '\n'
- 'Generic classes implicitly inherit from "typing.Generic". The '
- 'base\n'
- 'classes and keyword arguments of generic classes are evaluated '
- 'within\n'
- 'the type scope for the type parameters, and decorators are '
- 'evaluated\n'
- 'outside that scope. This is illustrated by this example:\n'
- '\n'
- ' @decorator\n'
- ' class Bag(Base[T], arg=T): ...\n'
- '\n'
- 'This is equivalent to:\n'
- '\n'
- ' annotation-def TYPE_PARAMS_OF_Bag():\n'
- ' T = typing.TypeVar("T")\n'
- ' class Bag(Base[T], typing.Generic[T], arg=T):\n'
- ' __type_params__ = (T,)\n'
- ' ...\n'
- ' return Bag\n'
- ' Bag = decorator(TYPE_PARAMS_OF_Bag())\n'
- '\n'
- '\n'
- 'Generic type aliases\n'
- '--------------------\n'
- '\n'
- 'The "type" statement can also be used to create a generic type '
- 'alias:\n'
- '\n'
- ' type ListOrSet[T] = list[T] | set[T]\n'
- '\n'
- 'Except for the lazy evaluation of the value, this is equivalent '
- 'to:\n'
- '\n'
- ' annotation-def TYPE_PARAMS_OF_ListOrSet():\n'
- ' T = typing.TypeVar("T")\n'
- '\n'
- ' annotation-def VALUE_OF_ListOrSet():\n'
- ' return list[T] | set[T]\n'
- ' # In reality, the value is lazily evaluated\n'
- ' return typing.TypeAliasType("ListOrSet", '
- 'VALUE_OF_ListOrSet(), type_params=(T,))\n'
- ' ListOrSet = TYPE_PARAMS_OF_ListOrSet()\n'
- '\n'
- 'Here, "annotation-def" (not a real keyword) indicates an '
- 'annotation\n'
- 'scope. The capitalized names like "TYPE_PARAMS_OF_ListOrSet" are '
- 'not\n'
- 'actually bound at runtime.\n'
- '\n'
- '-[ Footnotes ]-\n'
- '\n'
- '[1] The exception is propagated to the invocation stack unless '
- 'there\n'
- ' is a "finally" clause which happens to raise another '
- 'exception.\n'
- ' That new exception causes the old one to be lost.\n'
- '\n'
- '[2] In pattern matching, a sequence is defined as one of the\n'
- ' following:\n'
- '\n'
- ' * a class that inherits from "collections.abc.Sequence"\n'
- '\n'
- ' * a Python class that has been registered as\n'
- ' "collections.abc.Sequence"\n'
- '\n'
- ' * a builtin class that has its (CPython) '
- '"Py_TPFLAGS_SEQUENCE" bit\n'
- ' set\n'
- '\n'
- ' * a class that inherits from any of the above\n'
- '\n'
- ' The following standard library classes are sequences:\n'
- '\n'
- ' * "array.array"\n'
- '\n'
- ' * "collections.deque"\n'
- '\n'
- ' * "list"\n'
- '\n'
- ' * "memoryview"\n'
- '\n'
- ' * "range"\n'
- '\n'
- ' * "tuple"\n'
- '\n'
- ' Note:\n'
- '\n'
- ' Subject values of type "str", "bytes", and "bytearray" do '
- 'not\n'
- ' match sequence patterns.\n'
- '\n'
- '[3] In pattern matching, a mapping is defined as one of the '
- 'following:\n'
- '\n'
- ' * a class that inherits from "collections.abc.Mapping"\n'
- '\n'
- ' * a Python class that has been registered as\n'
- ' "collections.abc.Mapping"\n'
- '\n'
- ' * a builtin class that has its (CPython) '
- '"Py_TPFLAGS_MAPPING" bit\n'
- ' set\n'
- '\n'
- ' * a class that inherits from any of the above\n'
- '\n'
- ' The standard library classes "dict" and '
- '"types.MappingProxyType"\n'
- ' are mappings.\n'
- '\n'
- '[4] A string literal appearing as the first statement in the '
- 'function\n'
- ' body is transformed into the function’s "__doc__" attribute '
- 'and\n'
- ' therefore the function’s *docstring*.\n'
- '\n'
- '[5] A string literal appearing as the first statement in the '
- 'class\n'
- ' body is transformed into the namespace’s "__doc__" item and\n'
- ' therefore the class’s *docstring*.\n',
- 'context-managers': 'With Statement Context Managers\n'
- '*******************************\n'
- '\n'
- 'A *context manager* is an object that defines the '
- 'runtime context to\n'
- 'be established when executing a "with" statement. The '
- 'context manager\n'
- 'handles the entry into, and the exit from, the desired '
- 'runtime context\n'
- 'for the execution of the block of code. Context '
- 'managers are normally\n'
- 'invoked using the "with" statement (described in section '
- 'The with\n'
- 'statement), but can also be used by directly invoking '
- 'their methods.\n'
- '\n'
- 'Typical uses of context managers include saving and '
- 'restoring various\n'
- 'kinds of global state, locking and unlocking resources, '
- 'closing opened\n'
- 'files, etc.\n'
- '\n'
- 'For more information on context managers, see Context '
- 'Manager Types.\n'
- 'The "object" class itself does not provide the context '
- 'manager\n'
- 'methods.\n'
- '\n'
- 'object.__enter__(self)\n'
- '\n'
- ' Enter the runtime context related to this object. The '
- '"with"\n'
- ' statement will bind this method’s return value to the '
- 'target(s)\n'
- ' specified in the "as" clause of the statement, if '
- 'any.\n'
- '\n'
- 'object.__exit__(self, exc_type, exc_value, traceback)\n'
- '\n'
- ' Exit the runtime context related to this object. The '
- 'parameters\n'
- ' describe the exception that caused the context to be '
- 'exited. If the\n'
- ' context was exited without an exception, all three '
- 'arguments will\n'
- ' be "None".\n'
- '\n'
- ' If an exception is supplied, and the method wishes to '
- 'suppress the\n'
- ' exception (i.e., prevent it from being propagated), '
- 'it should\n'
- ' return a true value. Otherwise, the exception will be '
- 'processed\n'
- ' normally upon exit from this method.\n'
- '\n'
- ' Note that "__exit__()" methods should not reraise the '
- 'passed-in\n'
- ' exception; this is the caller’s responsibility.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 343** - The “with” statement\n'
- ' The specification, background, and examples for the '
- 'Python "with"\n'
- ' statement.\n',
- 'continue': 'The "continue" statement\n'
- '************************\n'
- '\n'
- ' continue_stmt ::= "continue"\n'
- '\n'
- '"continue" may only occur syntactically nested in a "for" or '
- '"while"\n'
- 'loop, but not nested in a function or class definition within '
- 'that\n'
- 'loop. It continues with the next cycle of the nearest enclosing '
- 'loop.\n'
- '\n'
- 'When "continue" passes control out of a "try" statement with a\n'
- '"finally" clause, that "finally" clause is executed before '
- 'really\n'
- 'starting the next loop cycle.\n',
- 'conversions': 'Arithmetic conversions\n'
- '**********************\n'
- '\n'
- 'When a description of an arithmetic operator below uses the '
- 'phrase\n'
- '“the numeric arguments are converted to a common type”, this '
- 'means\n'
- 'that the operator implementation for built-in types works as '
- 'follows:\n'
- '\n'
- '* If either argument is a complex number, the other is '
- 'converted to\n'
- ' complex;\n'
- '\n'
- '* otherwise, if either argument is a floating-point number, '
- 'the other\n'
- ' is converted to floating point;\n'
- '\n'
- '* otherwise, both must be integers and no conversion is '
- 'necessary.\n'
- '\n'
- 'Some additional rules apply for certain operators (e.g., a '
- 'string as a\n'
- 'left argument to the ‘%’ operator). Extensions must define '
- 'their own\n'
- 'conversion behavior.\n',
- 'customization': 'Basic customization\n'
- '*******************\n'
- '\n'
- 'object.__new__(cls[, ...])\n'
- '\n'
- ' Called to create a new instance of class *cls*. '
- '"__new__()" is a\n'
- ' static method (special-cased so you need not declare it '
- 'as such)\n'
- ' that takes the class of which an instance was requested '
- 'as its\n'
- ' first argument. The remaining arguments are those '
- 'passed to the\n'
- ' object constructor expression (the call to the class). '
- 'The return\n'
- ' value of "__new__()" should be the new object instance '
- '(usually an\n'
- ' instance of *cls*).\n'
- '\n'
- ' Typical implementations create a new instance of the '
- 'class by\n'
- ' invoking the superclass’s "__new__()" method using\n'
- ' "super().__new__(cls[, ...])" with appropriate arguments '
- 'and then\n'
- ' modifying the newly created instance as necessary before '
- 'returning\n'
- ' it.\n'
- '\n'
- ' If "__new__()" is invoked during object construction and '
- 'it returns\n'
- ' an instance of *cls*, then the new instance’s '
- '"__init__()" method\n'
- ' will be invoked like "__init__(self[, ...])", where '
- '*self* is the\n'
- ' new instance and the remaining arguments are the same as '
- 'were\n'
- ' passed to the object constructor.\n'
- '\n'
- ' If "__new__()" does not return an instance of *cls*, '
- 'then the new\n'
- ' instance’s "__init__()" method will not be invoked.\n'
- '\n'
- ' "__new__()" is intended mainly to allow subclasses of '
- 'immutable\n'
- ' types (like int, str, or tuple) to customize instance '
- 'creation. It\n'
- ' is also commonly overridden in custom metaclasses in '
- 'order to\n'
- ' customize class creation.\n'
- '\n'
- 'object.__init__(self[, ...])\n'
- '\n'
- ' Called after the instance has been created (by '
- '"__new__()"), but\n'
- ' before it is returned to the caller. The arguments are '
- 'those\n'
- ' passed to the class constructor expression. If a base '
- 'class has an\n'
- ' "__init__()" method, the derived class’s "__init__()" '
- 'method, if\n'
- ' any, must explicitly call it to ensure proper '
- 'initialization of the\n'
- ' base class part of the instance; for example:\n'
- ' "super().__init__([args...])".\n'
- '\n'
- ' Because "__new__()" and "__init__()" work together in '
- 'constructing\n'
- ' objects ("__new__()" to create it, and "__init__()" to '
- 'customize\n'
- ' it), no non-"None" value may be returned by '
- '"__init__()"; doing so\n'
- ' will cause a "TypeError" to be raised at runtime.\n'
- '\n'
- 'object.__del__(self)\n'
- '\n'
- ' Called when the instance is about to be destroyed. This '
- 'is also\n'
- ' called a finalizer or (improperly) a destructor. If a '
- 'base class\n'
- ' has a "__del__()" method, the derived class’s '
- '"__del__()" method,\n'
- ' if any, must explicitly call it to ensure proper '
- 'deletion of the\n'
- ' base class part of the instance.\n'
- '\n'
- ' It is possible (though not recommended!) for the '
- '"__del__()" method\n'
- ' to postpone destruction of the instance by creating a '
- 'new reference\n'
- ' to it. This is called object *resurrection*. It is\n'
- ' implementation-dependent whether "__del__()" is called a '
- 'second\n'
- ' time when a resurrected object is about to be destroyed; '
- 'the\n'
- ' current *CPython* implementation only calls it once.\n'
- '\n'
- ' It is not guaranteed that "__del__()" methods are called '
- 'for\n'
- ' objects that still exist when the interpreter exits.\n'
- ' "weakref.finalize" provides a straightforward way to '
- 'register a\n'
- ' cleanup function to be called when an object is garbage '
- 'collected.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' "del x" doesn’t directly call "x.__del__()" — the '
- 'former\n'
- ' decrements the reference count for "x" by one, and the '
- 'latter is\n'
- ' only called when "x"’s reference count reaches zero.\n'
- '\n'
- ' **CPython implementation detail:** It is possible for a '
- 'reference\n'
- ' cycle to prevent the reference count of an object from '
- 'going to\n'
- ' zero. In this case, the cycle will be later detected '
- 'and deleted\n'
- ' by the *cyclic garbage collector*. A common cause of '
- 'reference\n'
- ' cycles is when an exception has been caught in a local '
- 'variable.\n'
- ' The frame’s locals then reference the exception, which '
- 'references\n'
- ' its own traceback, which references the locals of all '
- 'frames caught\n'
- ' in the traceback.\n'
- '\n'
- ' See also: Documentation for the "gc" module.\n'
- '\n'
- ' Warning:\n'
- '\n'
- ' Due to the precarious circumstances under which '
- '"__del__()"\n'
- ' methods are invoked, exceptions that occur during '
- 'their execution\n'
- ' are ignored, and a warning is printed to "sys.stderr" '
- 'instead.\n'
- ' In particular:\n'
- '\n'
- ' * "__del__()" can be invoked when arbitrary code is '
- 'being\n'
- ' executed, including from any arbitrary thread. If '
- '"__del__()"\n'
- ' needs to take a lock or invoke any other blocking '
- 'resource, it\n'
- ' may deadlock as the resource may already be taken by '
- 'the code\n'
- ' that gets interrupted to execute "__del__()".\n'
- '\n'
- ' * "__del__()" can be executed during interpreter '
- 'shutdown. As a\n'
- ' consequence, the global variables it needs to access '
- '(including\n'
- ' other modules) may already have been deleted or set '
- 'to "None".\n'
- ' Python guarantees that globals whose name begins '
- 'with a single\n'
- ' underscore are deleted from their module before '
- 'other globals\n'
- ' are deleted; if no other references to such globals '
- 'exist, this\n'
- ' may help in assuring that imported modules are still '
- 'available\n'
- ' at the time when the "__del__()" method is called.\n'
- '\n'
- 'object.__repr__(self)\n'
- '\n'
- ' Called by the "repr()" built-in function to compute the '
- '“official”\n'
- ' string representation of an object. If at all possible, '
- 'this\n'
- ' should look like a valid Python expression that could be '
- 'used to\n'
- ' recreate an object with the same value (given an '
- 'appropriate\n'
- ' environment). If this is not possible, a string of the '
- 'form\n'
- ' "<...some useful description...>" should be returned. '
- 'The return\n'
- ' value must be a string object. If a class defines '
- '"__repr__()" but\n'
- ' not "__str__()", then "__repr__()" is also used when an '
- '“informal”\n'
- ' string representation of instances of that class is '
- 'required.\n'
- '\n'
- ' This is typically used for debugging, so it is important '
- 'that the\n'
- ' representation is information-rich and unambiguous. A '
- 'default\n'
- ' implementation is provided by the "object" class '
- 'itself.\n'
- '\n'
- 'object.__str__(self)\n'
- '\n'
- ' Called by "str(object)", the default "__format__()" '
- 'implementation,\n'
- ' and the built-in function "print()", to compute the '
- '“informal” or\n'
- ' nicely printable string representation of an object. '
- 'The return\n'
- ' value must be a str object.\n'
- '\n'
- ' This method differs from "object.__repr__()" in that '
- 'there is no\n'
- ' expectation that "__str__()" return a valid Python '
- 'expression: a\n'
- ' more convenient or concise representation can be used.\n'
- '\n'
- ' The default implementation defined by the built-in type '
- '"object"\n'
- ' calls "object.__repr__()".\n'
- '\n'
- 'object.__bytes__(self)\n'
- '\n'
- ' Called by bytes to compute a byte-string representation '
- 'of an\n'
- ' object. This should return a "bytes" object. The '
- '"object" class\n'
- ' itself does not provide this method.\n'
- '\n'
- 'object.__format__(self, format_spec)\n'
- '\n'
- ' Called by the "format()" built-in function, and by '
- 'extension,\n'
- ' evaluation of formatted string literals and the '
- '"str.format()"\n'
- ' method, to produce a “formatted” string representation '
- 'of an\n'
- ' object. The *format_spec* argument is a string that '
- 'contains a\n'
- ' description of the formatting options desired. The '
- 'interpretation\n'
- ' of the *format_spec* argument is up to the type '
- 'implementing\n'
- ' "__format__()", however most classes will either '
- 'delegate\n'
- ' formatting to one of the built-in types, or use a '
- 'similar\n'
- ' formatting option syntax.\n'
- '\n'
- ' See Format Specification Mini-Language for a description '
- 'of the\n'
- ' standard formatting syntax.\n'
- '\n'
- ' The return value must be a string object.\n'
- '\n'
- ' The default implementation by the "object" class should '
- 'be given an\n'
- ' empty *format_spec* string. It delegates to '
- '"__str__()".\n'
- '\n'
- ' Changed in version 3.4: The __format__ method of '
- '"object" itself\n'
- ' raises a "TypeError" if passed any non-empty string.\n'
- '\n'
- ' Changed in version 3.7: "object.__format__(x, \'\')" is '
- 'now\n'
- ' equivalent to "str(x)" rather than "format(str(x), '
- '\'\')".\n'
- '\n'
- 'object.__lt__(self, other)\n'
- 'object.__le__(self, other)\n'
- 'object.__eq__(self, other)\n'
- 'object.__ne__(self, other)\n'
- 'object.__gt__(self, other)\n'
- 'object.__ge__(self, other)\n'
- '\n'
- ' These are the so-called “rich comparison” methods. The\n'
- ' correspondence between operator symbols and method names '
- 'is as\n'
- ' follows: "x<y" calls "x.__lt__(y)", "x<=y" calls '
- '"x.__le__(y)",\n'
- ' "x==y" calls "x.__eq__(y)", "x!=y" calls "x.__ne__(y)", '
- '"x>y" calls\n'
- ' "x.__gt__(y)", and "x>=y" calls "x.__ge__(y)".\n'
- '\n'
- ' A rich comparison method may return the singleton '
- '"NotImplemented"\n'
- ' if it does not implement the operation for a given pair '
- 'of\n'
- ' arguments. By convention, "False" and "True" are '
- 'returned for a\n'
- ' successful comparison. However, these methods can return '
- 'any value,\n'
- ' so if the comparison operator is used in a Boolean '
- 'context (e.g.,\n'
- ' in the condition of an "if" statement), Python will call '
- '"bool()"\n'
- ' on the value to determine if the result is true or '
- 'false.\n'
- '\n'
- ' By default, "object" implements "__eq__()" by using '
- '"is", returning\n'
- ' "NotImplemented" in the case of a false comparison: '
- '"True if x is y\n'
- ' else NotImplemented". For "__ne__()", by default it '
- 'delegates to\n'
- ' "__eq__()" and inverts the result unless it is '
- '"NotImplemented".\n'
- ' There are no other implied relationships among the '
- 'comparison\n'
- ' operators or default implementations; for example, the '
- 'truth of\n'
- ' "(x<y or x==y)" does not imply "x<=y". To automatically '
- 'generate\n'
- ' ordering operations from a single root operation, see\n'
- ' "functools.total_ordering()".\n'
- '\n'
- ' By default, the "object" class provides implementations '
- 'consistent\n'
- ' with Value comparisons: equality compares according to '
- 'object\n'
- ' identity, and order comparisons raise "TypeError". Each '
- 'default\n'
- ' method may generate these results directly, but may also '
- 'return\n'
- ' "NotImplemented".\n'
- '\n'
- ' See the paragraph on "__hash__()" for some important '
- 'notes on\n'
- ' creating *hashable* objects which support custom '
- 'comparison\n'
- ' operations and are usable as dictionary keys.\n'
- '\n'
- ' There are no swapped-argument versions of these methods '
- '(to be used\n'
- ' when the left argument does not support the operation '
- 'but the right\n'
- ' argument does); rather, "__lt__()" and "__gt__()" are '
- 'each other’s\n'
- ' reflection, "__le__()" and "__ge__()" are each other’s '
- 'reflection,\n'
- ' and "__eq__()" and "__ne__()" are their own reflection. '
- 'If the\n'
- ' operands are of different types, and the right operand’s '
- 'type is a\n'
- ' direct or indirect subclass of the left operand’s type, '
- 'the\n'
- ' reflected method of the right operand has priority, '
- 'otherwise the\n'
- ' left operand’s method has priority. Virtual subclassing '
- 'is not\n'
- ' considered.\n'
- '\n'
- ' When no appropriate method returns any value other than\n'
- ' "NotImplemented", the "==" and "!=" operators will fall '
- 'back to\n'
- ' "is" and "is not", respectively.\n'
- '\n'
- 'object.__hash__(self)\n'
- '\n'
- ' Called by built-in function "hash()" and for operations '
- 'on members\n'
- ' of hashed collections including "set", "frozenset", and '
- '"dict".\n'
- ' The "__hash__()" method should return an integer. The '
- 'only required\n'
- ' property is that objects which compare equal have the '
- 'same hash\n'
- ' value; it is advised to mix together the hash values of '
- 'the\n'
- ' components of the object that also play a part in '
- 'comparison of\n'
- ' objects by packing them into a tuple and hashing the '
- 'tuple.\n'
- ' Example:\n'
- '\n'
- ' def __hash__(self):\n'
- ' return hash((self.name, self.nick, self.color))\n'
- '\n'
- ' Note:\n'
- '\n'
- ' "hash()" truncates the value returned from an object’s '
- 'custom\n'
- ' "__hash__()" method to the size of a "Py_ssize_t". '
- 'This is\n'
- ' typically 8 bytes on 64-bit builds and 4 bytes on '
- '32-bit builds.\n'
- ' If an object’s "__hash__()" must interoperate on '
- 'builds of\n'
- ' different bit sizes, be sure to check the width on all '
- 'supported\n'
- ' builds. An easy way to do this is with "python -c '
- '"import sys;\n'
- ' print(sys.hash_info.width)"".\n'
- '\n'
- ' If a class does not define an "__eq__()" method it '
- 'should not\n'
- ' define a "__hash__()" operation either; if it defines '
- '"__eq__()"\n'
- ' but not "__hash__()", its instances will not be usable '
- 'as items in\n'
- ' hashable collections. If a class defines mutable '
- 'objects and\n'
- ' implements an "__eq__()" method, it should not '
- 'implement\n'
- ' "__hash__()", since the implementation of *hashable* '
- 'collections\n'
- ' requires that a key’s hash value is immutable (if the '
- 'object’s hash\n'
- ' value changes, it will be in the wrong hash bucket).\n'
- '\n'
- ' User-defined classes have "__eq__()" and "__hash__()" '
- 'methods by\n'
- ' default (inherited from the "object" class); with them, '
- 'all objects\n'
- ' compare unequal (except with themselves) and '
- '"x.__hash__()" returns\n'
- ' an appropriate value such that "x == y" implies both '
- 'that "x is y"\n'
- ' and "hash(x) == hash(y)".\n'
- '\n'
- ' A class that overrides "__eq__()" and does not define '
- '"__hash__()"\n'
- ' will have its "__hash__()" implicitly set to "None". '
- 'When the\n'
- ' "__hash__()" method of a class is "None", instances of '
- 'the class\n'
- ' will raise an appropriate "TypeError" when a program '
- 'attempts to\n'
- ' retrieve their hash value, and will also be correctly '
- 'identified as\n'
- ' unhashable when checking "isinstance(obj,\n'
- ' collections.abc.Hashable)".\n'
- '\n'
- ' If a class that overrides "__eq__()" needs to retain '
- 'the\n'
- ' implementation of "__hash__()" from a parent class, the '
- 'interpreter\n'
- ' must be told this explicitly by setting "__hash__ =\n'
- ' <ParentClass>.__hash__".\n'
- '\n'
- ' If a class that does not override "__eq__()" wishes to '
- 'suppress\n'
- ' hash support, it should include "__hash__ = None" in the '
- 'class\n'
- ' definition. A class which defines its own "__hash__()" '
- 'that\n'
- ' explicitly raises a "TypeError" would be incorrectly '
- 'identified as\n'
- ' hashable by an "isinstance(obj, '
- 'collections.abc.Hashable)" call.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' By default, the "__hash__()" values of str and bytes '
- 'objects are\n'
- ' “salted” with an unpredictable random value. Although '
- 'they\n'
- ' remain constant within an individual Python process, '
- 'they are not\n'
- ' predictable between repeated invocations of '
- 'Python.This is\n'
- ' intended to provide protection against a '
- 'denial-of-service caused\n'
- ' by carefully chosen inputs that exploit the worst '
- 'case\n'
- ' performance of a dict insertion, *O*(*n*^2) '
- 'complexity. See\n'
- ' http://ocert.org/advisories/ocert-2011-003.html for\n'
- ' details.Changing hash values affects the iteration '
- 'order of sets.\n'
- ' Python has never made guarantees about this ordering '
- '(and it\n'
- ' typically varies between 32-bit and 64-bit builds).See '
- 'also\n'
- ' "PYTHONHASHSEED".\n'
- '\n'
- ' Changed in version 3.3: Hash randomization is enabled by '
- 'default.\n'
- '\n'
- 'object.__bool__(self)\n'
- '\n'
- ' Called to implement truth value testing and the built-in '
- 'operation\n'
- ' "bool()"; should return "False" or "True". When this '
- 'method is not\n'
- ' defined, "__len__()" is called, if it is defined, and '
- 'the object is\n'
- ' considered true if its result is nonzero. If a class '
- 'defines\n'
- ' neither "__len__()" nor "__bool__()" (which is true of '
- 'the "object"\n'
- ' class itself), all its instances are considered true.\n',
- 'debugger': '"pdb" — The Python Debugger\n'
- '***************************\n'
- '\n'
- '**Source code:** Lib/pdb.py\n'
- '\n'
- '======================================================================\n'
- '\n'
- 'The module "pdb" defines an interactive source code debugger '
- 'for\n'
- 'Python programs. It supports setting (conditional) breakpoints '
- 'and\n'
- 'single stepping at the source line level, inspection of stack '
- 'frames,\n'
- 'source code listing, and evaluation of arbitrary Python code in '
- 'the\n'
- 'context of any stack frame. It also supports post-mortem '
- 'debugging\n'
- 'and can be called under program control.\n'
- '\n'
- 'The debugger is extensible – it is actually defined as the '
- 'class\n'
- '"Pdb". This is currently undocumented but easily understood by '
- 'reading\n'
- 'the source. The extension interface uses the modules "bdb" and '
- '"cmd".\n'
- '\n'
- 'See also:\n'
- '\n'
- ' Module "faulthandler"\n'
- ' Used to dump Python tracebacks explicitly, on a fault, '
- 'after a\n'
- ' timeout, or on a user signal.\n'
- '\n'
- ' Module "traceback"\n'
- ' Standard interface to extract, format and print stack '
- 'traces of\n'
- ' Python programs.\n'
- '\n'
- 'The typical usage to break into the debugger is to insert:\n'
- '\n'
- ' import pdb; pdb.set_trace()\n'
- '\n'
- 'Or:\n'
- '\n'
- ' breakpoint()\n'
- '\n'
- 'at the location you want to break into the debugger, and then '
- 'run the\n'
- 'program. You can then step through the code following this '
- 'statement,\n'
- 'and continue running without the debugger using the "continue"\n'
- 'command.\n'
- '\n'
- 'Changed in version 3.7: The built-in "breakpoint()", when called '
- 'with\n'
- 'defaults, can be used instead of "import pdb; pdb.set_trace()".\n'
- '\n'
- ' def double(x):\n'
- ' breakpoint()\n'
- ' return x * 2\n'
- ' val = 3\n'
- ' print(f"{val} * 2 is {double(val)}")\n'
- '\n'
- 'The debugger’s prompt is "(Pdb)", which is the indicator that '
- 'you are\n'
- 'in debug mode:\n'
- '\n'
- ' > ...(3)double()\n'
- ' -> return x * 2\n'
- ' (Pdb) p x\n'
- ' 3\n'
- ' (Pdb) continue\n'
- ' 3 * 2 is 6\n'
- '\n'
- 'Changed in version 3.3: Tab-completion via the "readline" module '
- 'is\n'
- 'available for commands and command arguments, e.g. the current '
- 'global\n'
- 'and local names are offered as arguments of the "p" command.\n'
- '\n'
- 'You can also invoke "pdb" from the command line to debug other\n'
- 'scripts. For example:\n'
- '\n'
- ' python -m pdb myscript.py\n'
- '\n'
- 'When invoked as a module, pdb will automatically enter '
- 'post-mortem\n'
- 'debugging if the program being debugged exits abnormally. After '
- 'post-\n'
- 'mortem debugging (or after normal exit of the program), pdb '
- 'will\n'
- 'restart the program. Automatic restarting preserves pdb’s state '
- '(such\n'
- 'as breakpoints) and in most cases is more useful than quitting '
- 'the\n'
- 'debugger upon program’s exit.\n'
- '\n'
- 'Changed in version 3.2: Added the "-c" option to execute '
- 'commands as\n'
- 'if given in a ".pdbrc" file; see Debugger Commands.\n'
- '\n'
- 'Changed in version 3.7: Added the "-m" option to execute '
- 'modules\n'
- 'similar to the way "python -m" does. As with a script, the '
- 'debugger\n'
- 'will pause execution just before the first line of the module.\n'
- '\n'
- 'Typical usage to execute a statement under control of the '
- 'debugger is:\n'
- '\n'
- ' >>> import pdb\n'
- ' >>> def f(x):\n'
- ' ... print(1 / x)\n'
- ' >>> pdb.run("f(2)")\n'
- ' > <string>(1)<module>()\n'
- ' (Pdb) continue\n'
- ' 0.5\n'
- ' >>>\n'
- '\n'
- 'The typical usage to inspect a crashed program is:\n'
- '\n'
- ' >>> import pdb\n'
- ' >>> def f(x):\n'
- ' ... print(1 / x)\n'
- ' ...\n'
- ' >>> f(0)\n'
- ' Traceback (most recent call last):\n'
- ' File "<stdin>", line 1, in <module>\n'
- ' File "<stdin>", line 2, in f\n'
- ' ZeroDivisionError: division by zero\n'
- ' >>> pdb.pm()\n'
- ' > <stdin>(2)f()\n'
- ' (Pdb) p x\n'
- ' 0\n'
- ' (Pdb)\n'
- '\n'
- 'The module defines the following functions; each enters the '
- 'debugger\n'
- 'in a slightly different way:\n'
- '\n'
- 'pdb.run(statement, globals=None, locals=None)\n'
- '\n'
- ' Execute the *statement* (given as a string or a code object) '
- 'under\n'
- ' debugger control. The debugger prompt appears before any '
- 'code is\n'
- ' executed; you can set breakpoints and type "continue", or you '
- 'can\n'
- ' step through the statement using "step" or "next" (all these\n'
- ' commands are explained below). The optional *globals* and '
- '*locals*\n'
- ' arguments specify the environment in which the code is '
- 'executed; by\n'
- ' default the dictionary of the module "__main__" is used. '
- '(See the\n'
- ' explanation of the built-in "exec()" or "eval()" functions.)\n'
- '\n'
- 'pdb.runeval(expression, globals=None, locals=None)\n'
- '\n'
- ' Evaluate the *expression* (given as a string or a code '
- 'object)\n'
- ' under debugger control. When "runeval()" returns, it returns '
- 'the\n'
- ' value of the *expression*. Otherwise this function is '
- 'similar to\n'
- ' "run()".\n'
- '\n'
- 'pdb.runcall(function, *args, **kwds)\n'
- '\n'
- ' Call the *function* (a function or method object, not a '
- 'string)\n'
- ' with the given arguments. When "runcall()" returns, it '
- 'returns\n'
- ' whatever the function call returned. The debugger prompt '
- 'appears\n'
- ' as soon as the function is entered.\n'
- '\n'
- 'pdb.set_trace(*, header=None)\n'
- '\n'
- ' Enter the debugger at the calling stack frame. This is '
- 'useful to\n'
- ' hard-code a breakpoint at a given point in a program, even if '
- 'the\n'
- ' code is not otherwise being debugged (e.g. when an assertion\n'
- ' fails). If given, *header* is printed to the console just '
- 'before\n'
- ' debugging begins.\n'
- '\n'
- ' Changed in version 3.7: The keyword-only argument *header*.\n'
- '\n'
- 'pdb.post_mortem(traceback=None)\n'
- '\n'
- ' Enter post-mortem debugging of the given *traceback* object. '
- 'If no\n'
- ' *traceback* is given, it uses the one of the exception that '
- 'is\n'
- ' currently being handled (an exception must be being handled '
- 'if the\n'
- ' default is to be used).\n'
- '\n'
- 'pdb.pm()\n'
- '\n'
- ' Enter post-mortem debugging of the traceback found in\n'
- ' "sys.last_traceback".\n'
- '\n'
- 'The "run*" functions and "set_trace()" are aliases for '
- 'instantiating\n'
- 'the "Pdb" class and calling the method of the same name. If you '
- 'want\n'
- 'to access further features, you have to do this yourself:\n'
- '\n'
- "class pdb.Pdb(completekey='tab', stdin=None, stdout=None, "
- 'skip=None, nosigint=False, readrc=True)\n'
- '\n'
- ' "Pdb" is the debugger class.\n'
- '\n'
- ' The *completekey*, *stdin* and *stdout* arguments are passed '
- 'to the\n'
- ' underlying "cmd.Cmd" class; see the description there.\n'
- '\n'
- ' The *skip* argument, if given, must be an iterable of '
- 'glob-style\n'
- ' module name patterns. The debugger will not step into frames '
- 'that\n'
- ' originate in a module that matches one of these patterns. '
- '[1]\n'
- '\n'
- ' By default, Pdb sets a handler for the SIGINT signal (which '
- 'is sent\n'
- ' when the user presses "Ctrl-C" on the console) when you give '
- 'a\n'
- ' "continue" command. This allows you to break into the '
- 'debugger\n'
- ' again by pressing "Ctrl-C". If you want Pdb not to touch '
- 'the\n'
- ' SIGINT handler, set *nosigint* to true.\n'
- '\n'
- ' The *readrc* argument defaults to true and controls whether '
- 'Pdb\n'
- ' will load .pdbrc files from the filesystem.\n'
- '\n'
- ' Example call to enable tracing with *skip*:\n'
- '\n'
- " import pdb; pdb.Pdb(skip=['django.*']).set_trace()\n"
- '\n'
- ' Raises an auditing event "pdb.Pdb" with no arguments.\n'
- '\n'
- ' Changed in version 3.1: Added the *skip* parameter.\n'
- '\n'
- ' Changed in version 3.2: Added the *nosigint* parameter. '
- 'Previously,\n'
- ' a SIGINT handler was never set by Pdb.\n'
- '\n'
- ' Changed in version 3.6: The *readrc* argument.\n'
- '\n'
- ' run(statement, globals=None, locals=None)\n'
- ' runeval(expression, globals=None, locals=None)\n'
- ' runcall(function, *args, **kwds)\n'
- ' set_trace()\n'
- '\n'
- ' See the documentation for the functions explained above.\n'
- '\n'
- '\n'
- 'Debugger Commands\n'
- '=================\n'
- '\n'
- 'The commands recognized by the debugger are listed below. Most\n'
- 'commands can be abbreviated to one or two letters as indicated; '
- 'e.g.\n'
- '"h(elp)" means that either "h" or "help" can be used to enter '
- 'the help\n'
- 'command (but not "he" or "hel", nor "H" or "Help" or "HELP").\n'
- 'Arguments to commands must be separated by whitespace (spaces '
- 'or\n'
- 'tabs). Optional arguments are enclosed in square brackets '
- '("[]") in\n'
- 'the command syntax; the square brackets must not be typed.\n'
- 'Alternatives in the command syntax are separated by a vertical '
- 'bar\n'
- '("|").\n'
- '\n'
- 'Entering a blank line repeats the last command entered. '
- 'Exception: if\n'
- 'the last command was a "list" command, the next 11 lines are '
- 'listed.\n'
- '\n'
- 'Commands that the debugger doesn’t recognize are assumed to be '
- 'Python\n'
- 'statements and are executed in the context of the program being\n'
- 'debugged. Python statements can also be prefixed with an '
- 'exclamation\n'
- 'point ("!"). This is a powerful way to inspect the program '
- 'being\n'
- 'debugged; it is even possible to change a variable or call a '
- 'function.\n'
- 'When an exception occurs in such a statement, the exception name '
- 'is\n'
- 'printed but the debugger’s state is not changed.\n'
- '\n'
- 'The debugger supports aliases. Aliases can have parameters '
- 'which\n'
- 'allows one a certain level of adaptability to the context under\n'
- 'examination.\n'
- '\n'
- 'Multiple commands may be entered on a single line, separated by '
- '";;".\n'
- '(A single ";" is not used as it is the separator for multiple '
- 'commands\n'
- 'in a line that is passed to the Python parser.) No intelligence '
- 'is\n'
- 'applied to separating the commands; the input is split at the '
- 'first\n'
- '";;" pair, even if it is in the middle of a quoted string. A\n'
- 'workaround for strings with double semicolons is to use '
- 'implicit\n'
- 'string concatenation "\';\'\';\'" or "";"";"".\n'
- '\n'
- 'To set a temporary global variable, use a *convenience '
- 'variable*. A\n'
- '*convenience variable* is a variable whose name starts with '
- '"$". For\n'
- 'example, "$foo = 1" sets a global variable "$foo" which you can '
- 'use in\n'
- 'the debugger session. The *convenience variables* are cleared '
- 'when\n'
- 'the program resumes execution so it’s less likely to interfere '
- 'with\n'
- 'your program compared to using normal variables like "foo = 1".\n'
- '\n'
- 'There are three preset *convenience variables*:\n'
- '\n'
- '* "$_frame": the current frame you are debugging\n'
- '\n'
- '* "$_retval": the return value if the frame is returning\n'
- '\n'
- '* "$_exception": the exception if the frame is raising an '
- 'exception\n'
- '\n'
- 'Added in version 3.12: Added the *convenience variable* '
- 'feature.\n'
- '\n'
- 'If a file ".pdbrc" exists in the user’s home directory or in '
- 'the\n'
- 'current directory, it is read with "\'utf-8\'" encoding and '
- 'executed as\n'
- 'if it had been typed at the debugger prompt, with the exception '
- 'that\n'
- 'empty lines and lines starting with "#" are ignored. This is\n'
- 'particularly useful for aliases. If both files exist, the one '
- 'in the\n'
- 'home directory is read first and aliases defined there can be\n'
- 'overridden by the local file.\n'
- '\n'
- 'Changed in version 3.2: ".pdbrc" can now contain commands that\n'
- 'continue debugging, such as "continue" or "next". Previously, '
- 'these\n'
- 'commands had no effect.\n'
- '\n'
- 'Changed in version 3.11: ".pdbrc" is now read with "\'utf-8\'" '
- 'encoding.\n'
- 'Previously, it was read with the system locale encoding.\n'
- '\n'
- 'h(elp) [command]\n'
- '\n'
- ' Without argument, print the list of available commands. With '
- 'a\n'
- ' *command* as argument, print help about that command. "help '
- 'pdb"\n'
- ' displays the full documentation (the docstring of the "pdb"\n'
- ' module). Since the *command* argument must be an identifier, '
- '"help\n'
- ' exec" must be entered to get help on the "!" command.\n'
- '\n'
- 'w(here)\n'
- '\n'
- ' Print a stack trace, with the most recent frame at the '
- 'bottom. An\n'
- ' arrow (">") indicates the current frame, which determines '
- 'the\n'
- ' context of most commands.\n'
- '\n'
- 'd(own) [count]\n'
- '\n'
- ' Move the current frame *count* (default one) levels down in '
- 'the\n'
- ' stack trace (to a newer frame).\n'
- '\n'
- 'u(p) [count]\n'
- '\n'
- ' Move the current frame *count* (default one) levels up in the '
- 'stack\n'
- ' trace (to an older frame).\n'
- '\n'
- 'b(reak) [([filename:]lineno | function) [, condition]]\n'
- '\n'
- ' With a *lineno* argument, set a break there in the current '
- 'file.\n'
- ' With a *function* argument, set a break at the first '
- 'executable\n'
- ' statement within that function. The line number may be '
- 'prefixed\n'
- ' with a filename and a colon, to specify a breakpoint in '
- 'another\n'
- ' file (probably one that hasn’t been loaded yet). The file '
- 'is\n'
- ' searched on "sys.path". Note that each breakpoint is '
- 'assigned a\n'
- ' number to which all the other breakpoint commands refer.\n'
- '\n'
- ' If a second argument is present, it is an expression which '
- 'must\n'
- ' evaluate to true before the breakpoint is honored.\n'
- '\n'
- ' Without argument, list all breaks, including for each '
- 'breakpoint,\n'
- ' the number of times that breakpoint has been hit, the '
- 'current\n'
- ' ignore count, and the associated condition if any.\n'
- '\n'
- 'tbreak [([filename:]lineno | function) [, condition]]\n'
- '\n'
- ' Temporary breakpoint, which is removed automatically when it '
- 'is\n'
- ' first hit. The arguments are the same as for "break".\n'
- '\n'
- 'cl(ear) [filename:lineno | bpnumber ...]\n'
- '\n'
- ' With a *filename:lineno* argument, clear all the breakpoints '
- 'at\n'
- ' this line. With a space separated list of breakpoint numbers, '
- 'clear\n'
- ' those breakpoints. Without argument, clear all breaks (but '
- 'first\n'
- ' ask confirmation).\n'
- '\n'
- 'disable bpnumber [bpnumber ...]\n'
- '\n'
- ' Disable the breakpoints given as a space separated list of\n'
- ' breakpoint numbers. Disabling a breakpoint means it cannot '
- 'cause\n'
- ' the program to stop execution, but unlike clearing a '
- 'breakpoint, it\n'
- ' remains in the list of breakpoints and can be (re-)enabled.\n'
- '\n'
- 'enable bpnumber [bpnumber ...]\n'
- '\n'
- ' Enable the breakpoints specified.\n'
- '\n'
- 'ignore bpnumber [count]\n'
- '\n'
- ' Set the ignore count for the given breakpoint number. If '
- '*count*\n'
- ' is omitted, the ignore count is set to 0. A breakpoint '
- 'becomes\n'
- ' active when the ignore count is zero. When non-zero, the '
- '*count*\n'
- ' is decremented each time the breakpoint is reached and the\n'
- ' breakpoint is not disabled and any associated condition '
- 'evaluates\n'
- ' to true.\n'
- '\n'
- 'condition bpnumber [condition]\n'
- '\n'
- ' Set a new *condition* for the breakpoint, an expression which '
- 'must\n'
- ' evaluate to true before the breakpoint is honored. If '
- '*condition*\n'
- ' is absent, any existing condition is removed; i.e., the '
- 'breakpoint\n'
- ' is made unconditional.\n'
- '\n'
- 'commands [bpnumber]\n'
- '\n'
- ' Specify a list of commands for breakpoint number *bpnumber*. '
- 'The\n'
- ' commands themselves appear on the following lines. Type a '
- 'line\n'
- ' containing just "end" to terminate the commands. An example:\n'
- '\n'
- ' (Pdb) commands 1\n'
- ' (com) p some_variable\n'
- ' (com) end\n'
- ' (Pdb)\n'
- '\n'
- ' To remove all commands from a breakpoint, type "commands" '
- 'and\n'
- ' follow it immediately with "end"; that is, give no commands.\n'
- '\n'
- ' With no *bpnumber* argument, "commands" refers to the last\n'
- ' breakpoint set.\n'
- '\n'
- ' You can use breakpoint commands to start your program up '
- 'again.\n'
- ' Simply use the "continue" command, or "step", or any other '
- 'command\n'
- ' that resumes execution.\n'
- '\n'
- ' Specifying any command resuming execution (currently '
- '"continue",\n'
- ' "step", "next", "return", "jump", "quit" and their '
- 'abbreviations)\n'
- ' terminates the command list (as if that command was '
- 'immediately\n'
- ' followed by end). This is because any time you resume '
- 'execution\n'
- ' (even with a simple next or step), you may encounter another\n'
- ' breakpoint—which could have its own command list, leading to\n'
- ' ambiguities about which list to execute.\n'
- '\n'
- ' If you use the "silent" command in the command list, the '
- 'usual\n'
- ' message about stopping at a breakpoint is not printed. This '
- 'may be\n'
- ' desirable for breakpoints that are to print a specific '
- 'message and\n'
- ' then continue. If none of the other commands print anything, '
- 'you\n'
- ' see no sign that the breakpoint was reached.\n'
- '\n'
- 's(tep)\n'
- '\n'
- ' Execute the current line, stop at the first possible '
- 'occasion\n'
- ' (either in a function that is called or on the next line in '
- 'the\n'
- ' current function).\n'
- '\n'
- 'n(ext)\n'
- '\n'
- ' Continue execution until the next line in the current '
- 'function is\n'
- ' reached or it returns. (The difference between "next" and '
- '"step"\n'
- ' is that "step" stops inside a called function, while "next"\n'
- ' executes called functions at (nearly) full speed, only '
- 'stopping at\n'
- ' the next line in the current function.)\n'
- '\n'
- 'unt(il) [lineno]\n'
- '\n'
- ' Without argument, continue execution until the line with a '
- 'number\n'
- ' greater than the current one is reached.\n'
- '\n'
- ' With *lineno*, continue execution until a line with a number\n'
- ' greater or equal to *lineno* is reached. In both cases, also '
- 'stop\n'
- ' when the current frame returns.\n'
- '\n'
- ' Changed in version 3.2: Allow giving an explicit line '
- 'number.\n'
- '\n'
- 'r(eturn)\n'
- '\n'
- ' Continue execution until the current function returns.\n'
- '\n'
- 'c(ont(inue))\n'
- '\n'
- ' Continue execution, only stop when a breakpoint is '
- 'encountered.\n'
- '\n'
- 'j(ump) lineno\n'
- '\n'
- ' Set the next line that will be executed. Only available in '
- 'the\n'
- ' bottom-most frame. This lets you jump back and execute code '
- 'again,\n'
- ' or jump forward to skip code that you don’t want to run.\n'
- '\n'
- ' It should be noted that not all jumps are allowed – for '
- 'instance it\n'
- ' is not possible to jump into the middle of a "for" loop or '
- 'out of a\n'
- ' "finally" clause.\n'
- '\n'
- 'l(ist) [first[, last]]\n'
- '\n'
- ' List source code for the current file. Without arguments, '
- 'list 11\n'
- ' lines around the current line or continue the previous '
- 'listing.\n'
- ' With "." as argument, list 11 lines around the current line. '
- 'With\n'
- ' one argument, list 11 lines around at that line. With two\n'
- ' arguments, list the given range; if the second argument is '
- 'less\n'
- ' than the first, it is interpreted as a count.\n'
- '\n'
- ' The current line in the current frame is indicated by "->". '
- 'If an\n'
- ' exception is being debugged, the line where the exception '
- 'was\n'
- ' originally raised or propagated is indicated by ">>", if it '
- 'differs\n'
- ' from the current line.\n'
- '\n'
- ' Changed in version 3.2: Added the ">>" marker.\n'
- '\n'
- 'll | longlist\n'
- '\n'
- ' List all source code for the current function or frame.\n'
- ' Interesting lines are marked as for "list".\n'
- '\n'
- ' Added in version 3.2.\n'
- '\n'
- 'a(rgs)\n'
- '\n'
- ' Print the arguments of the current function and their '
- 'current\n'
- ' values.\n'
- '\n'
- 'p expression\n'
- '\n'
- ' Evaluate *expression* in the current context and print its '
- 'value.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' "print()" can also be used, but is not a debugger command — '
- 'this\n'
- ' executes the Python "print()" function.\n'
- '\n'
- 'pp expression\n'
- '\n'
- ' Like the "p" command, except the value of *expression* is '
- 'pretty-\n'
- ' printed using the "pprint" module.\n'
- '\n'
- 'whatis expression\n'
- '\n'
- ' Print the type of *expression*.\n'
- '\n'
- 'source expression\n'
- '\n'
- ' Try to get source code of *expression* and display it.\n'
- '\n'
- ' Added in version 3.2.\n'
- '\n'
- 'display [expression]\n'
- '\n'
- ' Display the value of *expression* if it changed, each time\n'
- ' execution stops in the current frame.\n'
- '\n'
- ' Without *expression*, list all display expressions for the '
- 'current\n'
- ' frame.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' Display evaluates *expression* and compares to the result '
- 'of the\n'
- ' previous evaluation of *expression*, so when the result is\n'
- ' mutable, display may not be able to pick up the changes.\n'
- '\n'
- ' Example:\n'
- '\n'
- ' lst = []\n'
- ' breakpoint()\n'
- ' pass\n'
- ' lst.append(1)\n'
- ' print(lst)\n'
- '\n'
- ' Display won’t realize "lst" has been changed because the '
- 'result of\n'
- ' evaluation is modified in place by "lst.append(1)" before '
- 'being\n'
- ' compared:\n'
- '\n'
- ' > example.py(3)<module>()\n'
- ' -> pass\n'
- ' (Pdb) display lst\n'
- ' display lst: []\n'
- ' (Pdb) n\n'
- ' > example.py(4)<module>()\n'
- ' -> lst.append(1)\n'
- ' (Pdb) n\n'
- ' > example.py(5)<module>()\n'
- ' -> print(lst)\n'
- ' (Pdb)\n'
- '\n'
- ' You can do some tricks with copy mechanism to make it work:\n'
- '\n'
- ' > example.py(3)<module>()\n'
- ' -> pass\n'
- ' (Pdb) display lst[:]\n'
- ' display lst[:]: []\n'
- ' (Pdb) n\n'
- ' > example.py(4)<module>()\n'
- ' -> lst.append(1)\n'
- ' (Pdb) n\n'
- ' > example.py(5)<module>()\n'
- ' -> print(lst)\n'
- ' display lst[:]: [1] [old: []]\n'
- ' (Pdb)\n'
- '\n'
- ' Added in version 3.2.\n'
- '\n'
- 'undisplay [expression]\n'
- '\n'
- ' Do not display *expression* anymore in the current frame. '
- 'Without\n'
- ' *expression*, clear all display expressions for the current '
- 'frame.\n'
- '\n'
- ' Added in version 3.2.\n'
- '\n'
- 'interact\n'
- '\n'
- ' Start an interactive interpreter (using the "code" module) '
- 'whose\n'
- ' global namespace contains all the (global and local) names '
- 'found in\n'
- ' the current scope.\n'
- '\n'
- ' Added in version 3.2.\n'
- '\n'
- 'alias [name [command]]\n'
- '\n'
- ' Create an alias called *name* that executes *command*. The\n'
- ' *command* must *not* be enclosed in quotes. Replaceable '
- 'parameters\n'
- ' can be indicated by "%1", "%2", and so on, while "%*" is '
- 'replaced\n'
- ' by all the parameters. If *command* is omitted, the current '
- 'alias\n'
- ' for *name* is shown. If no arguments are given, all aliases '
- 'are\n'
- ' listed.\n'
- '\n'
- ' Aliases may be nested and can contain anything that can be '
- 'legally\n'
- ' typed at the pdb prompt. Note that internal pdb commands '
- '*can* be\n'
- ' overridden by aliases. Such a command is then hidden until '
- 'the\n'
- ' alias is removed. Aliasing is recursively applied to the '
- 'first\n'
- ' word of the command line; all other words in the line are '
- 'left\n'
- ' alone.\n'
- '\n'
- ' As an example, here are two useful aliases (especially when '
- 'placed\n'
- ' in the ".pdbrc" file):\n'
- '\n'
- ' # Print instance variables (usage "pi classInst")\n'
- ' alias pi for k in %1.__dict__.keys(): print(f"%1.{k} = '
- '{%1.__dict__[k]}")\n'
- ' # Print instance variables in self\n'
- ' alias ps pi self\n'
- '\n'
- 'unalias name\n'
- '\n'
- ' Delete the specified alias *name*.\n'
- '\n'
- '! statement\n'
- '\n'
- ' Execute the (one-line) *statement* in the context of the '
- 'current\n'
- ' stack frame. The exclamation point can be omitted unless the '
- 'first\n'
- ' word of the statement resembles a debugger command, e.g.:\n'
- '\n'
- ' (Pdb) ! n=42\n'
- ' (Pdb)\n'
- '\n'
- ' To set a global variable, you can prefix the assignment '
- 'command\n'
- ' with a "global" statement on the same line, e.g.:\n'
- '\n'
- " (Pdb) global list_options; list_options = ['-l']\n"
- ' (Pdb)\n'
- '\n'
- 'run [args ...]\n'
- 'restart [args ...]\n'
- '\n'
- ' Restart the debugged Python program. If *args* is supplied, '
- 'it is\n'
- ' split with "shlex" and the result is used as the new '
- '"sys.argv".\n'
- ' History, breakpoints, actions and debugger options are '
- 'preserved.\n'
- ' "restart" is an alias for "run".\n'
- '\n'
- 'q(uit)\n'
- '\n'
- ' Quit from the debugger. The program being executed is '
- 'aborted.\n'
- '\n'
- 'debug code\n'
- '\n'
- ' Enter a recursive debugger that steps through *code* (which '
- 'is an\n'
- ' arbitrary expression or statement to be executed in the '
- 'current\n'
- ' environment).\n'
- '\n'
- 'retval\n'
- '\n'
- ' Print the return value for the last return of the current '
- 'function.\n'
- '\n'
- '-[ Footnotes ]-\n'
- '\n'
- '[1] Whether a frame is considered to originate in a certain '
- 'module is\n'
- ' determined by the "__name__" in the frame globals.\n',
- 'del': 'The "del" statement\n'
- '*******************\n'
- '\n'
- ' del_stmt ::= "del" target_list\n'
- '\n'
- 'Deletion is recursively defined very similar to the way assignment '
- 'is\n'
- 'defined. Rather than spelling it out in full details, here are some\n'
- 'hints.\n'
- '\n'
- 'Deletion of a target list recursively deletes each target, from left\n'
- 'to right.\n'
- '\n'
- 'Deletion of a name removes the binding of that name from the local '
- 'or\n'
- 'global namespace, depending on whether the name occurs in a "global"\n'
- 'statement in the same code block. If the name is unbound, a\n'
- '"NameError" exception will be raised.\n'
- '\n'
- 'Deletion of attribute references, subscriptions and slicings is '
- 'passed\n'
- 'to the primary object involved; deletion of a slicing is in general\n'
- 'equivalent to assignment of an empty slice of the right type (but '
- 'even\n'
- 'this is determined by the sliced object).\n'
- '\n'
- 'Changed in version 3.2: Previously it was illegal to delete a name\n'
- 'from the local namespace if it occurs as a free variable in a nested\n'
- 'block.\n',
- 'dict': 'Dictionary displays\n'
- '*******************\n'
- '\n'
- 'A dictionary display is a possibly empty series of dict items\n'
- '(key/value pairs) enclosed in curly braces:\n'
- '\n'
- ' dict_display ::= "{" [dict_item_list | dict_comprehension] '
- '"}"\n'
- ' dict_item_list ::= dict_item ("," dict_item)* [","]\n'
- ' dict_item ::= expression ":" expression | "**" or_expr\n'
- ' dict_comprehension ::= expression ":" expression comp_for\n'
- '\n'
- 'A dictionary display yields a new dictionary object.\n'
- '\n'
- 'If a comma-separated sequence of dict items is given, they are\n'
- 'evaluated from left to right to define the entries of the '
- 'dictionary:\n'
- 'each key object is used as a key into the dictionary to store the\n'
- 'corresponding value. This means that you can specify the same key\n'
- 'multiple times in the dict item list, and the final dictionary’s '
- 'value\n'
- 'for that key will be the last one given.\n'
- '\n'
- 'A double asterisk "**" denotes *dictionary unpacking*. Its operand\n'
- 'must be a *mapping*. Each mapping item is added to the new\n'
- 'dictionary. Later values replace values already set by earlier '
- 'dict\n'
- 'items and earlier dictionary unpackings.\n'
- '\n'
- 'Added in version 3.5: Unpacking into dictionary displays, '
- 'originally\n'
- 'proposed by **PEP 448**.\n'
- '\n'
- 'A dict comprehension, in contrast to list and set comprehensions,\n'
- 'needs two expressions separated with a colon followed by the usual\n'
- '“for” and “if” clauses. When the comprehension is run, the '
- 'resulting\n'
- 'key and value elements are inserted in the new dictionary in the '
- 'order\n'
- 'they are produced.\n'
- '\n'
- 'Restrictions on the types of the key values are listed earlier in\n'
- 'section The standard type hierarchy. (To summarize, the key type\n'
- 'should be *hashable*, which excludes all mutable objects.) Clashes\n'
- 'between duplicate keys are not detected; the last value (textually\n'
- 'rightmost in the display) stored for a given key value prevails.\n'
- '\n'
- 'Changed in version 3.8: Prior to Python 3.8, in dict '
- 'comprehensions,\n'
- 'the evaluation order of key and value was not well-defined. In\n'
- 'CPython, the value was evaluated before the key. Starting with '
- '3.8,\n'
- 'the key is evaluated before the value, as proposed by **PEP 572**.\n',
- 'dynamic-features': 'Interaction with dynamic features\n'
- '*********************************\n'
- '\n'
- 'Name resolution of free variables occurs at runtime, not '
- 'at compile\n'
- 'time. This means that the following code will print 42:\n'
- '\n'
- ' i = 10\n'
- ' def f():\n'
- ' print(i)\n'
- ' i = 42\n'
- ' f()\n'
- '\n'
- 'The "eval()" and "exec()" functions do not have access '
- 'to the full\n'
- 'environment for resolving names. Names may be resolved '
- 'in the local\n'
- 'and global namespaces of the caller. Free variables are '
- 'not resolved\n'
- 'in the nearest enclosing namespace, but in the global '
- 'namespace. [1]\n'
- 'The "exec()" and "eval()" functions have optional '
- 'arguments to\n'
- 'override the global and local namespace. If only one '
- 'namespace is\n'
- 'specified, it is used for both.\n',
- 'else': 'The "if" statement\n'
- '******************\n'
- '\n'
- 'The "if" statement is used for conditional execution:\n'
- '\n'
- ' if_stmt ::= "if" assignment_expression ":" suite\n'
- ' ("elif" assignment_expression ":" suite)*\n'
- ' ["else" ":" suite]\n'
- '\n'
- 'It selects exactly one of the suites by evaluating the expressions '
- 'one\n'
- 'by one until one is found to be true (see section Boolean '
- 'operations\n'
- 'for the definition of true and false); then that suite is executed\n'
- '(and no other part of the "if" statement is executed or evaluated).\n'
- 'If all expressions are false, the suite of the "else" clause, if\n'
- 'present, is executed.\n',
- 'exceptions': 'Exceptions\n'
- '**********\n'
- '\n'
- 'Exceptions are a means of breaking out of the normal flow of '
- 'control\n'
- 'of a code block in order to handle errors or other '
- 'exceptional\n'
- 'conditions. An exception is *raised* at the point where the '
- 'error is\n'
- 'detected; it may be *handled* by the surrounding code block or '
- 'by any\n'
- 'code block that directly or indirectly invoked the code block '
- 'where\n'
- 'the error occurred.\n'
- '\n'
- 'The Python interpreter raises an exception when it detects a '
- 'run-time\n'
- 'error (such as division by zero). A Python program can also\n'
- 'explicitly raise an exception with the "raise" statement. '
- 'Exception\n'
- 'handlers are specified with the "try" … "except" statement. '
- 'The\n'
- '"finally" clause of such a statement can be used to specify '
- 'cleanup\n'
- 'code which does not handle the exception, but is executed '
- 'whether an\n'
- 'exception occurred or not in the preceding code.\n'
- '\n'
- 'Python uses the “termination” model of error handling: an '
- 'exception\n'
- 'handler can find out what happened and continue execution at '
- 'an outer\n'
- 'level, but it cannot repair the cause of the error and retry '
- 'the\n'
- 'failing operation (except by re-entering the offending piece '
- 'of code\n'
- 'from the top).\n'
- '\n'
- 'When an exception is not handled at all, the interpreter '
- 'terminates\n'
- 'execution of the program, or returns to its interactive main '
- 'loop. In\n'
- 'either case, it prints a stack traceback, except when the '
- 'exception is\n'
- '"SystemExit".\n'
- '\n'
- 'Exceptions are identified by class instances. The "except" '
- 'clause is\n'
- 'selected depending on the class of the instance: it must '
- 'reference the\n'
- 'class of the instance or a *non-virtual base class* thereof. '
- 'The\n'
- 'instance can be received by the handler and can carry '
- 'additional\n'
- 'information about the exceptional condition.\n'
- '\n'
- 'Note:\n'
- '\n'
- ' Exception messages are not part of the Python API. Their '
- 'contents\n'
- ' may change from one version of Python to the next without '
- 'warning\n'
- ' and should not be relied on by code which will run under '
- 'multiple\n'
- ' versions of the interpreter.\n'
- '\n'
- 'See also the description of the "try" statement in section The '
- 'try\n'
- 'statement and "raise" statement in section The raise '
- 'statement.\n'
- '\n'
- '-[ Footnotes ]-\n'
- '\n'
- '[1] This limitation occurs because the code that is executed '
- 'by these\n'
- ' operations is not available at the time the module is '
- 'compiled.\n',
- 'execmodel': 'Execution model\n'
- '***************\n'
- '\n'
- '\n'
- 'Structure of a program\n'
- '======================\n'
- '\n'
- 'A Python program is constructed from code blocks. A *block* is '
- 'a piece\n'
- 'of Python program text that is executed as a unit. The '
- 'following are\n'
- 'blocks: a module, a function body, and a class definition. '
- 'Each\n'
- 'command typed interactively is a block. A script file (a file '
- 'given\n'
- 'as standard input to the interpreter or specified as a command '
- 'line\n'
- 'argument to the interpreter) is a code block. A script command '
- '(a\n'
- 'command specified on the interpreter command line with the '
- '"-c"\n'
- 'option) is a code block. A module run as a top level script (as '
- 'module\n'
- '"__main__") from the command line using a "-m" argument is also '
- 'a code\n'
- 'block. The string argument passed to the built-in functions '
- '"eval()"\n'
- 'and "exec()" is a code block.\n'
- '\n'
- 'A code block is executed in an *execution frame*. A frame '
- 'contains\n'
- 'some administrative information (used for debugging) and '
- 'determines\n'
- 'where and how execution continues after the code block’s '
- 'execution has\n'
- 'completed.\n'
- '\n'
- '\n'
- 'Naming and binding\n'
- '==================\n'
- '\n'
- '\n'
- 'Binding of names\n'
- '----------------\n'
- '\n'
- '*Names* refer to objects. Names are introduced by name '
- 'binding\n'
- 'operations.\n'
- '\n'
- 'The following constructs bind names:\n'
- '\n'
- '* formal parameters to functions,\n'
- '\n'
- '* class definitions,\n'
- '\n'
- '* function definitions,\n'
- '\n'
- '* assignment expressions,\n'
- '\n'
- '* targets that are identifiers if occurring in an assignment:\n'
- '\n'
- ' * "for" loop header,\n'
- '\n'
- ' * after "as" in a "with" statement, "except" clause, '
- '"except*"\n'
- ' clause, or in the as-pattern in structural pattern '
- 'matching,\n'
- '\n'
- ' * in a capture pattern in structural pattern matching\n'
- '\n'
- '* "import" statements.\n'
- '\n'
- '* "type" statements.\n'
- '\n'
- '* type parameter lists.\n'
- '\n'
- 'The "import" statement of the form "from ... import *" binds '
- 'all names\n'
- 'defined in the imported module, except those beginning with an\n'
- 'underscore. This form may only be used at the module level.\n'
- '\n'
- 'A target occurring in a "del" statement is also considered '
- 'bound for\n'
- 'this purpose (though the actual semantics are to unbind the '
- 'name).\n'
- '\n'
- 'Each assignment or import statement occurs within a block '
- 'defined by a\n'
- 'class or function definition or at the module level (the '
- 'top-level\n'
- 'code block).\n'
- '\n'
- 'If a name is bound in a block, it is a local variable of that '
- 'block,\n'
- 'unless declared as "nonlocal" or "global". If a name is bound '
- 'at the\n'
- 'module level, it is a global variable. (The variables of the '
- 'module\n'
- 'code block are local and global.) If a variable is used in a '
- 'code\n'
- 'block but not defined there, it is a *free variable*.\n'
- '\n'
- 'Each occurrence of a name in the program text refers to the '
- '*binding*\n'
- 'of that name established by the following name resolution '
- 'rules.\n'
- '\n'
- '\n'
- 'Resolution of names\n'
- '-------------------\n'
- '\n'
- 'A *scope* defines the visibility of a name within a block. If '
- 'a local\n'
- 'variable is defined in a block, its scope includes that block. '
- 'If the\n'
- 'definition occurs in a function block, the scope extends to any '
- 'blocks\n'
- 'contained within the defining one, unless a contained block '
- 'introduces\n'
- 'a different binding for the name.\n'
- '\n'
- 'When a name is used in a code block, it is resolved using the '
- 'nearest\n'
- 'enclosing scope. The set of all such scopes visible to a code '
- 'block\n'
- 'is called the block’s *environment*.\n'
- '\n'
- 'When a name is not found at all, a "NameError" exception is '
- 'raised. If\n'
- 'the current scope is a function scope, and the name refers to a '
- 'local\n'
- 'variable that has not yet been bound to a value at the point '
- 'where the\n'
- 'name is used, an "UnboundLocalError" exception is raised.\n'
- '"UnboundLocalError" is a subclass of "NameError".\n'
- '\n'
- 'If a name binding operation occurs anywhere within a code '
- 'block, all\n'
- 'uses of the name within the block are treated as references to '
- 'the\n'
- 'current block. This can lead to errors when a name is used '
- 'within a\n'
- 'block before it is bound. This rule is subtle. Python lacks\n'
- 'declarations and allows name binding operations to occur '
- 'anywhere\n'
- 'within a code block. The local variables of a code block can '
- 'be\n'
- 'determined by scanning the entire text of the block for name '
- 'binding\n'
- 'operations. See the FAQ entry on UnboundLocalError for '
- 'examples.\n'
- '\n'
- 'If the "global" statement occurs within a block, all uses of '
- 'the names\n'
- 'specified in the statement refer to the bindings of those names '
- 'in the\n'
- 'top-level namespace. Names are resolved in the top-level '
- 'namespace by\n'
- 'searching the global namespace, i.e. the namespace of the '
- 'module\n'
- 'containing the code block, and the builtins namespace, the '
- 'namespace\n'
- 'of the module "builtins". The global namespace is searched '
- 'first. If\n'
- 'the names are not found there, the builtins namespace is '
- 'searched\n'
- 'next. If the names are also not found in the builtins '
- 'namespace, new\n'
- 'variables are created in the global namespace. The global '
- 'statement\n'
- 'must precede all uses of the listed names.\n'
- '\n'
- 'The "global" statement has the same scope as a name binding '
- 'operation\n'
- 'in the same block. If the nearest enclosing scope for a free '
- 'variable\n'
- 'contains a global statement, the free variable is treated as a '
- 'global.\n'
- '\n'
- 'The "nonlocal" statement causes corresponding names to refer '
- 'to\n'
- 'previously bound variables in the nearest enclosing function '
- 'scope.\n'
- '"SyntaxError" is raised at compile time if the given name does '
- 'not\n'
- 'exist in any enclosing function scope. Type parameters cannot '
- 'be\n'
- 'rebound with the "nonlocal" statement.\n'
- '\n'
- 'The namespace for a module is automatically created the first '
- 'time a\n'
- 'module is imported. The main module for a script is always '
- 'called\n'
- '"__main__".\n'
- '\n'
- 'Class definition blocks and arguments to "exec()" and "eval()" '
- 'are\n'
- 'special in the context of name resolution. A class definition '
- 'is an\n'
- 'executable statement that may use and define names. These '
- 'references\n'
- 'follow the normal rules for name resolution with an exception '
- 'that\n'
- 'unbound local variables are looked up in the global namespace. '
- 'The\n'
- 'namespace of the class definition becomes the attribute '
- 'dictionary of\n'
- 'the class. The scope of names defined in a class block is '
- 'limited to\n'
- 'the class block; it does not extend to the code blocks of '
- 'methods.\n'
- 'This includes comprehensions and generator expressions, but it '
- 'does\n'
- 'not include annotation scopes, which have access to their '
- 'enclosing\n'
- 'class scopes. This means that the following will fail:\n'
- '\n'
- ' class A:\n'
- ' a = 42\n'
- ' b = list(a + i for i in range(10))\n'
- '\n'
- 'However, the following will succeed:\n'
- '\n'
- ' class A:\n'
- ' type Alias = Nested\n'
- ' class Nested: pass\n'
- '\n'
- " print(A.Alias.__value__) # <type 'A.Nested'>\n"
- '\n'
- '\n'
- 'Annotation scopes\n'
- '-----------------\n'
- '\n'
- 'Type parameter lists and "type" statements introduce '
- '*annotation\n'
- 'scopes*, which behave mostly like function scopes, but with '
- 'some\n'
- 'exceptions discussed below. *Annotations* currently do not use\n'
- 'annotation scopes, but they are expected to use annotation '
- 'scopes in\n'
- 'Python 3.13 when **PEP 649** is implemented.\n'
- '\n'
- 'Annotation scopes are used in the following contexts:\n'
- '\n'
- '* Type parameter lists for generic type aliases.\n'
- '\n'
- '* Type parameter lists for generic functions. A generic '
- 'function’s\n'
- ' annotations are executed within the annotation scope, but '
- 'its\n'
- ' defaults and decorators are not.\n'
- '\n'
- '* Type parameter lists for generic classes. A generic class’s '
- 'base\n'
- ' classes and keyword arguments are executed within the '
- 'annotation\n'
- ' scope, but its decorators are not.\n'
- '\n'
- '* The bounds and constraints for type variables (lazily '
- 'evaluated).\n'
- '\n'
- '* The value of type aliases (lazily evaluated).\n'
- '\n'
- 'Annotation scopes differ from function scopes in the following '
- 'ways:\n'
- '\n'
- '* Annotation scopes have access to their enclosing class '
- 'namespace. If\n'
- ' an annotation scope is immediately within a class scope, or '
- 'within\n'
- ' another annotation scope that is immediately within a class '
- 'scope,\n'
- ' the code in the annotation scope can use names defined in the '
- 'class\n'
- ' scope as if it were executed directly within the class body. '
- 'This\n'
- ' contrasts with regular functions defined within classes, '
- 'which\n'
- ' cannot access names defined in the class scope.\n'
- '\n'
- '* Expressions in annotation scopes cannot contain "yield", '
- '"yield\n'
- ' from", "await", or ":=" expressions. (These expressions are '
- 'allowed\n'
- ' in other scopes contained within the annotation scope.)\n'
- '\n'
- '* Names defined in annotation scopes cannot be rebound with '
- '"nonlocal"\n'
- ' statements in inner scopes. This includes only type '
- 'parameters, as\n'
- ' no other syntactic elements that can appear within annotation '
- 'scopes\n'
- ' can introduce new names.\n'
- '\n'
- '* While annotation scopes have an internal name, that name is '
- 'not\n'
- ' reflected in the *qualified name* of objects defined within '
- 'the\n'
- ' scope. Instead, the "__qualname__" of such objects is as if '
- 'the\n'
- ' object were defined in the enclosing scope.\n'
- '\n'
- 'Added in version 3.12: Annotation scopes were introduced in '
- 'Python\n'
- '3.12 as part of **PEP 695**.\n'
- '\n'
- '\n'
- 'Lazy evaluation\n'
- '---------------\n'
- '\n'
- 'The values of type aliases created through the "type" statement '
- 'are\n'
- '*lazily evaluated*. The same applies to the bounds and '
- 'constraints of\n'
- 'type variables created through the type parameter syntax. This '
- 'means\n'
- 'that they are not evaluated when the type alias or type '
- 'variable is\n'
- 'created. Instead, they are only evaluated when doing so is '
- 'necessary\n'
- 'to resolve an attribute access.\n'
- '\n'
- 'Example:\n'
- '\n'
- ' >>> type Alias = 1/0\n'
- ' >>> Alias.__value__\n'
- ' Traceback (most recent call last):\n'
- ' ...\n'
- ' ZeroDivisionError: division by zero\n'
- ' >>> def func[T: 1/0](): pass\n'
- ' >>> T = func.__type_params__[0]\n'
- ' >>> T.__bound__\n'
- ' Traceback (most recent call last):\n'
- ' ...\n'
- ' ZeroDivisionError: division by zero\n'
- '\n'
- 'Here the exception is raised only when the "__value__" '
- 'attribute of\n'
- 'the type alias or the "__bound__" attribute of the type '
- 'variable is\n'
- 'accessed.\n'
- '\n'
- 'This behavior is primarily useful for references to types that '
- 'have\n'
- 'not yet been defined when the type alias or type variable is '
- 'created.\n'
- 'For example, lazy evaluation enables creation of mutually '
- 'recursive\n'
- 'type aliases:\n'
- '\n'
- ' from typing import Literal\n'
- '\n'
- ' type SimpleExpr = int | Parenthesized\n'
- ' type Parenthesized = tuple[Literal["("], Expr, '
- 'Literal[")"]]\n'
- ' type Expr = SimpleExpr | tuple[SimpleExpr, Literal["+", '
- '"-"], Expr]\n'
- '\n'
- 'Lazily evaluated values are evaluated in annotation scope, '
- 'which means\n'
- 'that names that appear inside the lazily evaluated value are '
- 'looked up\n'
- 'as if they were used in the immediately enclosing scope.\n'
- '\n'
- 'Added in version 3.12.\n'
- '\n'
- '\n'
- 'Builtins and restricted execution\n'
- '---------------------------------\n'
- '\n'
- '**CPython implementation detail:** Users should not touch\n'
- '"__builtins__"; it is strictly an implementation detail. '
- 'Users\n'
- 'wanting to override values in the builtins namespace should '
- '"import"\n'
- 'the "builtins" module and modify its attributes appropriately.\n'
- '\n'
- 'The builtins namespace associated with the execution of a code '
- 'block\n'
- 'is actually found by looking up the name "__builtins__" in its '
- 'global\n'
- 'namespace; this should be a dictionary or a module (in the '
- 'latter case\n'
- 'the module’s dictionary is used). By default, when in the '
- '"__main__"\n'
- 'module, "__builtins__" is the built-in module "builtins"; when '
- 'in any\n'
- 'other module, "__builtins__" is an alias for the dictionary of '
- 'the\n'
- '"builtins" module itself.\n'
- '\n'
- '\n'
- 'Interaction with dynamic features\n'
- '---------------------------------\n'
- '\n'
- 'Name resolution of free variables occurs at runtime, not at '
- 'compile\n'
- 'time. This means that the following code will print 42:\n'
- '\n'
- ' i = 10\n'
- ' def f():\n'
- ' print(i)\n'
- ' i = 42\n'
- ' f()\n'
- '\n'
- 'The "eval()" and "exec()" functions do not have access to the '
- 'full\n'
- 'environment for resolving names. Names may be resolved in the '
- 'local\n'
- 'and global namespaces of the caller. Free variables are not '
- 'resolved\n'
- 'in the nearest enclosing namespace, but in the global '
- 'namespace. [1]\n'
- 'The "exec()" and "eval()" functions have optional arguments to\n'
- 'override the global and local namespace. If only one namespace '
- 'is\n'
- 'specified, it is used for both.\n'
- '\n'
- '\n'
- 'Exceptions\n'
- '==========\n'
- '\n'
- 'Exceptions are a means of breaking out of the normal flow of '
- 'control\n'
- 'of a code block in order to handle errors or other exceptional\n'
- 'conditions. An exception is *raised* at the point where the '
- 'error is\n'
- 'detected; it may be *handled* by the surrounding code block or '
- 'by any\n'
- 'code block that directly or indirectly invoked the code block '
- 'where\n'
- 'the error occurred.\n'
- '\n'
- 'The Python interpreter raises an exception when it detects a '
- 'run-time\n'
- 'error (such as division by zero). A Python program can also\n'
- 'explicitly raise an exception with the "raise" statement. '
- 'Exception\n'
- 'handlers are specified with the "try" … "except" statement. '
- 'The\n'
- '"finally" clause of such a statement can be used to specify '
- 'cleanup\n'
- 'code which does not handle the exception, but is executed '
- 'whether an\n'
- 'exception occurred or not in the preceding code.\n'
- '\n'
- 'Python uses the “termination” model of error handling: an '
- 'exception\n'
- 'handler can find out what happened and continue execution at an '
- 'outer\n'
- 'level, but it cannot repair the cause of the error and retry '
- 'the\n'
- 'failing operation (except by re-entering the offending piece of '
- 'code\n'
- 'from the top).\n'
- '\n'
- 'When an exception is not handled at all, the interpreter '
- 'terminates\n'
- 'execution of the program, or returns to its interactive main '
- 'loop. In\n'
- 'either case, it prints a stack traceback, except when the '
- 'exception is\n'
- '"SystemExit".\n'
- '\n'
- 'Exceptions are identified by class instances. The "except" '
- 'clause is\n'
- 'selected depending on the class of the instance: it must '
- 'reference the\n'
- 'class of the instance or a *non-virtual base class* thereof. '
- 'The\n'
- 'instance can be received by the handler and can carry '
- 'additional\n'
- 'information about the exceptional condition.\n'
- '\n'
- 'Note:\n'
- '\n'
- ' Exception messages are not part of the Python API. Their '
- 'contents\n'
- ' may change from one version of Python to the next without '
- 'warning\n'
- ' and should not be relied on by code which will run under '
- 'multiple\n'
- ' versions of the interpreter.\n'
- '\n'
- 'See also the description of the "try" statement in section The '
- 'try\n'
- 'statement and "raise" statement in section The raise '
- 'statement.\n'
- '\n'
- '-[ Footnotes ]-\n'
- '\n'
- '[1] This limitation occurs because the code that is executed by '
- 'these\n'
- ' operations is not available at the time the module is '
- 'compiled.\n',
- 'exprlists': 'Expression lists\n'
- '****************\n'
- '\n'
- ' starred_expression ::= ["*"] or_expr\n'
- ' flexible_expression ::= assignment_expression | '
- 'starred_expression\n'
- ' flexible_expression_list ::= flexible_expression ("," '
- 'flexible_expression)* [","]\n'
- ' starred_expression_list ::= starred_expression ("," '
- 'starred_expression)* [","]\n'
- ' expression_list ::= expression ("," expression)* '
- '[","]\n'
- ' yield_list ::= expression_list | '
- 'starred_expression "," [starred_expression_list]\n'
- '\n'
- 'Except when part of a list or set display, an expression list\n'
- 'containing at least one comma yields a tuple. The length of '
- 'the tuple\n'
- 'is the number of expressions in the list. The expressions are\n'
- 'evaluated from left to right.\n'
- '\n'
- 'An asterisk "*" denotes *iterable unpacking*. Its operand must '
- 'be an\n'
- '*iterable*. The iterable is expanded into a sequence of items, '
- 'which\n'
- 'are included in the new tuple, list, or set, at the site of '
- 'the\n'
- 'unpacking.\n'
- '\n'
- 'Added in version 3.5: Iterable unpacking in expression lists,\n'
- 'originally proposed by **PEP 448**.\n'
- '\n'
- 'Added in version 3.11: Any item in an expression list may be '
- 'starred.\n'
- 'See **PEP 646**.\n'
- '\n'
- 'A trailing comma is required only to create a one-item tuple, '
- 'such as\n'
- '"1,"; it is optional in all other cases. A single expression '
- 'without a\n'
- 'trailing comma doesn’t create a tuple, but rather yields the '
- 'value of\n'
- 'that expression. (To create an empty tuple, use an empty pair '
- 'of\n'
- 'parentheses: "()".)\n',
- 'floating': 'Floating-point literals\n'
- '***********************\n'
- '\n'
- 'Floating-point literals are described by the following lexical\n'
- 'definitions:\n'
- '\n'
- ' floatnumber ::= pointfloat | exponentfloat\n'
- ' pointfloat ::= [digitpart] fraction | digitpart "."\n'
- ' exponentfloat ::= (digitpart | pointfloat) exponent\n'
- ' digitpart ::= digit (["_"] digit)*\n'
- ' fraction ::= "." digitpart\n'
- ' exponent ::= ("e" | "E") ["+" | "-"] digitpart\n'
- '\n'
- 'Note that the integer and exponent parts are always interpreted '
- 'using\n'
- 'radix 10. For example, "077e010" is legal, and denotes the same '
- 'number\n'
- 'as "77e10". The allowed range of floating-point literals is\n'
- 'implementation-dependent. As in integer literals, underscores '
- 'are\n'
- 'supported for digit grouping.\n'
- '\n'
- 'Some examples of floating-point literals:\n'
- '\n'
- ' 3.14 10. .001 1e100 3.14e-10 0e0 '
- '3.14_15_93\n'
- '\n'
- 'Changed in version 3.6: Underscores are now allowed for '
- 'grouping\n'
- 'purposes in literals.\n',
- 'for': 'The "for" statement\n'
- '*******************\n'
- '\n'
- 'The "for" statement is used to iterate over the elements of a '
- 'sequence\n'
- '(such as a string, tuple or list) or other iterable object:\n'
- '\n'
- ' for_stmt ::= "for" target_list "in" starred_list ":" suite\n'
- ' ["else" ":" suite]\n'
- '\n'
- 'The "starred_list" expression is evaluated once; it should yield an\n'
- '*iterable* object. An *iterator* is created for that iterable. The\n'
- 'first item provided by the iterator is then assigned to the target\n'
- 'list using the standard rules for assignments (see Assignment\n'
- 'statements), and the suite is executed. This repeats for each item\n'
- 'provided by the iterator. When the iterator is exhausted, the suite\n'
- 'in the "else" clause, if present, is executed, and the loop\n'
- 'terminates.\n'
- '\n'
- 'A "break" statement executed in the first suite terminates the loop\n'
- 'without executing the "else" clause’s suite. A "continue" statement\n'
- 'executed in the first suite skips the rest of the suite and '
- 'continues\n'
- 'with the next item, or with the "else" clause if there is no next\n'
- 'item.\n'
- '\n'
- 'The for-loop makes assignments to the variables in the target list.\n'
- 'This overwrites all previous assignments to those variables '
- 'including\n'
- 'those made in the suite of the for-loop:\n'
- '\n'
- ' for i in range(10):\n'
- ' print(i)\n'
- ' i = 5 # this will not affect the for-loop\n'
- ' # because i will be overwritten with the '
- 'next\n'
- ' # index in the range\n'
- '\n'
- 'Names in the target list are not deleted when the loop is finished,\n'
- 'but if the sequence is empty, they will not have been assigned to at\n'
- 'all by the loop. Hint: the built-in type "range()" represents\n'
- 'immutable arithmetic sequences of integers. For instance, iterating\n'
- '"range(3)" successively yields 0, 1, and then 2.\n'
- '\n'
- 'Changed in version 3.11: Starred elements are now allowed in the\n'
- 'expression list.\n',
- 'formatstrings': 'Format String Syntax\n'
- '********************\n'
- '\n'
- 'The "str.format()" method and the "Formatter" class share '
- 'the same\n'
- 'syntax for format strings (although in the case of '
- '"Formatter",\n'
- 'subclasses can define their own format string syntax). The '
- 'syntax is\n'
- 'related to that of formatted string literals, but it is '
- 'less\n'
- 'sophisticated and, in particular, does not support '
- 'arbitrary\n'
- 'expressions.\n'
- '\n'
- 'Format strings contain “replacement fields” surrounded by '
- 'curly braces\n'
- '"{}". Anything that is not contained in braces is '
- 'considered literal\n'
- 'text, which is copied unchanged to the output. If you need '
- 'to include\n'
- 'a brace character in the literal text, it can be escaped by '
- 'doubling:\n'
- '"{{" and "}}".\n'
- '\n'
- 'The grammar for a replacement field is as follows:\n'
- '\n'
- ' replacement_field ::= "{" [field_name] ["!" conversion] '
- '[":" format_spec] "}"\n'
- ' field_name ::= arg_name ("." attribute_name | "[" '
- 'element_index "]")*\n'
- ' arg_name ::= [identifier | digit+]\n'
- ' attribute_name ::= identifier\n'
- ' element_index ::= digit+ | index_string\n'
- ' index_string ::= <any source character except "]"> '
- '+\n'
- ' conversion ::= "r" | "s" | "a"\n'
- ' format_spec ::= format-spec:format_spec\n'
- '\n'
- 'In less formal terms, the replacement field can start with '
- 'a\n'
- '*field_name* that specifies the object whose value is to be '
- 'formatted\n'
- 'and inserted into the output instead of the replacement '
- 'field. The\n'
- '*field_name* is optionally followed by a *conversion* '
- 'field, which is\n'
- 'preceded by an exclamation point "\'!\'", and a '
- '*format_spec*, which is\n'
- 'preceded by a colon "\':\'". These specify a non-default '
- 'format for the\n'
- 'replacement value.\n'
- '\n'
- 'See also the Format Specification Mini-Language section.\n'
- '\n'
- 'The *field_name* itself begins with an *arg_name* that is '
- 'either a\n'
- 'number or a keyword. If it’s a number, it refers to a '
- 'positional\n'
- 'argument, and if it’s a keyword, it refers to a named '
- 'keyword\n'
- 'argument. An *arg_name* is treated as a number if a call '
- 'to\n'
- '"str.isdecimal()" on the string would return true. If the '
- 'numerical\n'
- 'arg_names in a format string are 0, 1, 2, … in sequence, '
- 'they can all\n'
- 'be omitted (not just some) and the numbers 0, 1, 2, … will '
- 'be\n'
- 'automatically inserted in that order. Because *arg_name* is '
- 'not quote-\n'
- 'delimited, it is not possible to specify arbitrary '
- 'dictionary keys\n'
- '(e.g., the strings "\'10\'" or "\':-]\'") within a format '
- 'string. The\n'
- '*arg_name* can be followed by any number of index or '
- 'attribute\n'
- 'expressions. An expression of the form "\'.name\'" selects '
- 'the named\n'
- 'attribute using "getattr()", while an expression of the '
- 'form\n'
- '"\'[index]\'" does an index lookup using "__getitem__()".\n'
- '\n'
- 'Changed in version 3.1: The positional argument specifiers '
- 'can be\n'
- 'omitted for "str.format()", so "\'{} {}\'.format(a, b)" is '
- 'equivalent to\n'
- '"\'{0} {1}\'.format(a, b)".\n'
- '\n'
- 'Changed in version 3.4: The positional argument specifiers '
- 'can be\n'
- 'omitted for "Formatter".\n'
- '\n'
- 'Some simple format string examples:\n'
- '\n'
- ' "First, thou shalt count to {0}" # References first '
- 'positional argument\n'
- ' "Bring me a {}" # Implicitly '
- 'references the first positional argument\n'
- ' "From {} to {}" # Same as "From {0} to '
- '{1}"\n'
- ' "My quest is {name}" # References keyword '
- "argument 'name'\n"
- ' "Weight in tons {0.weight}" # \'weight\' attribute '
- 'of first positional arg\n'
- ' "Units destroyed: {players[0]}" # First element of '
- "keyword argument 'players'.\n"
- '\n'
- 'The *conversion* field causes a type coercion before '
- 'formatting.\n'
- 'Normally, the job of formatting a value is done by the '
- '"__format__()"\n'
- 'method of the value itself. However, in some cases it is '
- 'desirable to\n'
- 'force a type to be formatted as a string, overriding its '
- 'own\n'
- 'definition of formatting. By converting the value to a '
- 'string before\n'
- 'calling "__format__()", the normal formatting logic is '
- 'bypassed.\n'
- '\n'
- 'Three conversion flags are currently supported: "\'!s\'" '
- 'which calls\n'
- '"str()" on the value, "\'!r\'" which calls "repr()" and '
- '"\'!a\'" which\n'
- 'calls "ascii()".\n'
- '\n'
- 'Some examples:\n'
- '\n'
- ' "Harold\'s a clever {0!s}" # Calls str() on the '
- 'argument first\n'
- ' "Bring out the holy {name!r}" # Calls repr() on the '
- 'argument first\n'
- ' "More {!a}" # Calls ascii() on the '
- 'argument first\n'
- '\n'
- 'The *format_spec* field contains a specification of how the '
- 'value\n'
- 'should be presented, including such details as field width, '
- 'alignment,\n'
- 'padding, decimal precision and so on. Each value type can '
- 'define its\n'
- 'own “formatting mini-language” or interpretation of the '
- '*format_spec*.\n'
- '\n'
- 'Most built-in types support a common formatting '
- 'mini-language, which\n'
- 'is described in the next section.\n'
- '\n'
- 'A *format_spec* field can also include nested replacement '
- 'fields\n'
- 'within it. These nested replacement fields may contain a '
- 'field name,\n'
- 'conversion flag and format specification, but deeper '
- 'nesting is not\n'
- 'allowed. The replacement fields within the format_spec '
- 'are\n'
- 'substituted before the *format_spec* string is interpreted. '
- 'This\n'
- 'allows the formatting of a value to be dynamically '
- 'specified.\n'
- '\n'
- 'See the Format examples section for some examples.\n'
- '\n'
- '\n'
- 'Format Specification Mini-Language\n'
- '==================================\n'
- '\n'
- '“Format specifications” are used within replacement fields '
- 'contained\n'
- 'within a format string to define how individual values are '
- 'presented\n'
- '(see Format String Syntax and f-strings). They can also be '
- 'passed\n'
- 'directly to the built-in "format()" function. Each '
- 'formattable type\n'
- 'may define how the format specification is to be '
- 'interpreted.\n'
- '\n'
- 'Most built-in types implement the following options for '
- 'format\n'
- 'specifications, although some of the formatting options are '
- 'only\n'
- 'supported by the numeric types.\n'
- '\n'
- 'A general convention is that an empty format specification '
- 'produces\n'
- 'the same result as if you had called "str()" on the value. '
- 'A non-empty\n'
- 'format specification typically modifies the result.\n'
- '\n'
- 'The general form of a *standard format specifier* is:\n'
- '\n'
- ' format_spec ::= '
- '[[fill]align][sign]["z"]["#"]["0"][width][grouping_option]["." '
- 'precision][type]\n'
- ' fill ::= <any character>\n'
- ' align ::= "<" | ">" | "=" | "^"\n'
- ' sign ::= "+" | "-" | " "\n'
- ' width ::= digit+\n'
- ' grouping_option ::= "_" | ","\n'
- ' precision ::= digit+\n'
- ' type ::= "b" | "c" | "d" | "e" | "E" | "f" | '
- '"F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"\n'
- '\n'
- 'If a valid *align* value is specified, it can be preceded '
- 'by a *fill*\n'
- 'character that can be any character and defaults to a space '
- 'if\n'
- 'omitted. It is not possible to use a literal curly brace '
- '(”"{"” or\n'
- '“"}"”) as the *fill* character in a formatted string '
- 'literal or when\n'
- 'using the "str.format()" method. However, it is possible '
- 'to insert a\n'
- 'curly brace with a nested replacement field. This '
- 'limitation doesn’t\n'
- 'affect the "format()" function.\n'
- '\n'
- 'The meaning of the various alignment options is as '
- 'follows:\n'
- '\n'
- '+-----------+------------------------------------------------------------+\n'
- '| Option | '
- 'Meaning '
- '|\n'
- '|===========|============================================================|\n'
- '| "\'<\'" | Forces the field to be left-aligned within '
- 'the available |\n'
- '| | space (this is the default for most '
- 'objects). |\n'
- '+-----------+------------------------------------------------------------+\n'
- '| "\'>\'" | Forces the field to be right-aligned within '
- 'the available |\n'
- '| | space (this is the default for '
- 'numbers). |\n'
- '+-----------+------------------------------------------------------------+\n'
- '| "\'=\'" | Forces the padding to be placed after the '
- 'sign (if any) |\n'
- '| | but before the digits. This is used for '
- 'printing fields |\n'
- '| | in the form ‘+000000120’. This alignment '
- 'option is only |\n'
- '| | valid for numeric types, excluding "complex". '
- 'It becomes |\n'
- '| | the default for numbers when ‘0’ immediately '
- 'precedes the |\n'
- '| | field '
- 'width. |\n'
- '+-----------+------------------------------------------------------------+\n'
- '| "\'^\'" | Forces the field to be centered within the '
- 'available |\n'
- '| | '
- 'space. '
- '|\n'
- '+-----------+------------------------------------------------------------+\n'
- '\n'
- 'Note that unless a minimum field width is defined, the '
- 'field width\n'
- 'will always be the same size as the data to fill it, so '
- 'that the\n'
- 'alignment option has no meaning in this case.\n'
- '\n'
- 'The *sign* option is only valid for number types, and can '
- 'be one of\n'
- 'the following:\n'
- '\n'
- '+-----------+------------------------------------------------------------+\n'
- '| Option | '
- 'Meaning '
- '|\n'
- '|===========|============================================================|\n'
- '| "\'+\'" | indicates that a sign should be used for '
- 'both positive as |\n'
- '| | well as negative '
- 'numbers. |\n'
- '+-----------+------------------------------------------------------------+\n'
- '| "\'-\'" | indicates that a sign should be used only '
- 'for negative |\n'
- '| | numbers (this is the default '
- 'behavior). |\n'
- '+-----------+------------------------------------------------------------+\n'
- '| space | indicates that a leading space should be used '
- 'on positive |\n'
- '| | numbers, and a minus sign on negative '
- 'numbers. |\n'
- '+-----------+------------------------------------------------------------+\n'
- '\n'
- 'The "\'z\'" option coerces negative zero floating-point '
- 'values to\n'
- 'positive zero after rounding to the format precision. This '
- 'option is\n'
- 'only valid for floating-point presentation types.\n'
- '\n'
- 'Changed in version 3.11: Added the "\'z\'" option (see also '
- '**PEP\n'
- '682**).\n'
- '\n'
- 'The "\'#\'" option causes the “alternate form” to be used '
- 'for the\n'
- 'conversion. The alternate form is defined differently for '
- 'different\n'
- 'types. This option is only valid for integer, float and '
- 'complex\n'
- 'types. For integers, when binary, octal, or hexadecimal '
- 'output is\n'
- 'used, this option adds the respective prefix "\'0b\'", '
- '"\'0o\'", "\'0x\'",\n'
- 'or "\'0X\'" to the output value. For float and complex the '
- 'alternate\n'
- 'form causes the result of the conversion to always contain '
- 'a decimal-\n'
- 'point character, even if no digits follow it. Normally, a '
- 'decimal-\n'
- 'point character appears in the result of these conversions '
- 'only if a\n'
- 'digit follows it. In addition, for "\'g\'" and "\'G\'" '
- 'conversions,\n'
- 'trailing zeros are not removed from the result.\n'
- '\n'
- 'The "\',\'" option signals the use of a comma for a '
- 'thousands separator\n'
- 'for floating-point presentation types and for integer '
- 'presentation\n'
- 'type "\'d\'". For other presentation types, this option is '
- 'an error. For\n'
- 'a locale aware separator, use the "\'n\'" integer '
- 'presentation type\n'
- 'instead.\n'
- '\n'
- 'Changed in version 3.1: Added the "\',\'" option (see also '
- '**PEP 378**).\n'
- '\n'
- 'The "\'_\'" option signals the use of an underscore for a '
- 'thousands\n'
- 'separator for floating-point presentation types and for '
- 'integer\n'
- 'presentation type "\'d\'". For integer presentation types '
- '"\'b\'", "\'o\'",\n'
- '"\'x\'", and "\'X\'", underscores will be inserted every 4 '
- 'digits. For\n'
- 'other presentation types, specifying this option is an '
- 'error.\n'
- '\n'
- 'Changed in version 3.6: Added the "\'_\'" option (see also '
- '**PEP 515**).\n'
- '\n'
- '*width* is a decimal integer defining the minimum total '
- 'field width,\n'
- 'including any prefixes, separators, and other formatting '
- 'characters.\n'
- 'If not specified, then the field width will be determined '
- 'by the\n'
- 'content.\n'
- '\n'
- 'When no explicit alignment is given, preceding the *width* '
- 'field by a\n'
- 'zero ("\'0\'") character enables sign-aware zero-padding '
- 'for numeric\n'
- 'types, excluding "complex". This is equivalent to a *fill* '
- 'character\n'
- 'of "\'0\'" with an *alignment* type of "\'=\'".\n'
- '\n'
- 'Changed in version 3.10: Preceding the *width* field by '
- '"\'0\'" no\n'
- 'longer affects the default alignment for strings.\n'
- '\n'
- 'The *precision* is a decimal integer indicating how many '
- 'digits should\n'
- 'be displayed after the decimal point for presentation types '
- '"\'f\'" and\n'
- '"\'F\'", or before and after the decimal point for '
- 'presentation types\n'
- '"\'g\'" or "\'G\'". For string presentation types the '
- 'field indicates the\n'
- 'maximum field size - in other words, how many characters '
- 'will be used\n'
- 'from the field content. The *precision* is not allowed for '
- 'integer\n'
- 'presentation types.\n'
- '\n'
- 'Finally, the *type* determines how the data should be '
- 'presented.\n'
- '\n'
- 'The available string presentation types are:\n'
- '\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | Type | '
- 'Meaning '
- '|\n'
- ' '
- '|===========|============================================================|\n'
- ' | "\'s\'" | String format. This is the default type '
- 'for strings and |\n'
- ' | | may be '
- 'omitted. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | None | The same as '
- '"\'s\'". |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- '\n'
- 'The available integer presentation types are:\n'
- '\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | Type | '
- 'Meaning '
- '|\n'
- ' '
- '|===========|============================================================|\n'
- ' | "\'b\'" | Binary format. Outputs the number in '
- 'base 2. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'c\'" | Character. Converts the integer to the '
- 'corresponding |\n'
- ' | | unicode character before '
- 'printing. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'d\'" | Decimal Integer. Outputs the number in '
- 'base 10. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'o\'" | Octal format. Outputs the number in base '
- '8. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'x\'" | Hex format. Outputs the number in base '
- '16, using lower- |\n'
- ' | | case letters for the digits above '
- '9. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'X\'" | Hex format. Outputs the number in base '
- '16, using upper- |\n'
- ' | | case letters for the digits above 9. In '
- 'case "\'#\'" is |\n'
- ' | | specified, the prefix "\'0x\'" will be '
- 'upper-cased to "\'0X\'" |\n'
- ' | | as '
- 'well. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'n\'" | Number. This is the same as "\'d\'", '
- 'except that it uses the |\n'
- ' | | current locale setting to insert the '
- 'appropriate number |\n'
- ' | | separator '
- 'characters. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | None | The same as '
- '"\'d\'". |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- '\n'
- 'In addition to the above presentation types, integers can '
- 'be formatted\n'
- 'with the floating-point presentation types listed below '
- '(except "\'n\'"\n'
- 'and "None"). When doing so, "float()" is used to convert '
- 'the integer\n'
- 'to a floating-point number before formatting.\n'
- '\n'
- 'The available presentation types for "float" and "Decimal" '
- 'values are:\n'
- '\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | Type | '
- 'Meaning '
- '|\n'
- ' '
- '|===========|============================================================|\n'
- ' | "\'e\'" | Scientific notation. For a given '
- 'precision "p", formats |\n'
- ' | | the number in scientific notation with the '
- 'letter ‘e’ |\n'
- ' | | separating the coefficient from the '
- 'exponent. The |\n'
- ' | | coefficient has one digit before and "p" '
- 'digits after the |\n'
- ' | | decimal point, for a total of "p + 1" '
- 'significant digits. |\n'
- ' | | With no precision given, uses a precision '
- 'of "6" digits |\n'
- ' | | after the decimal point for "float", and '
- 'shows all |\n'
- ' | | coefficient digits for "Decimal". If '
- '"p=0", the decimal |\n'
- ' | | point is omitted unless the "#" option is '
- 'used. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'E\'" | Scientific notation. Same as "\'e\'" '
- 'except it uses an upper |\n'
- ' | | case ‘E’ as the separator '
- 'character. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'f\'" | Fixed-point notation. For a given '
- 'precision "p", formats |\n'
- ' | | the number as a decimal number with '
- 'exactly "p" digits |\n'
- ' | | following the decimal point. With no '
- 'precision given, uses |\n'
- ' | | a precision of "6" digits after the '
- 'decimal point for |\n'
- ' | | "float", and uses a precision large enough '
- 'to show all |\n'
- ' | | coefficient digits for "Decimal". If '
- '"p=0", the decimal |\n'
- ' | | point is omitted unless the "#" option is '
- 'used. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'F\'" | Fixed-point notation. Same as "\'f\'", '
- 'but converts "nan" to |\n'
- ' | | "NAN" and "inf" to '
- '"INF". |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'g\'" | General format. For a given precision '
- '"p >= 1", this |\n'
- ' | | rounds the number to "p" significant '
- 'digits and then |\n'
- ' | | formats the result in either fixed-point '
- 'format or in |\n'
- ' | | scientific notation, depending on its '
- 'magnitude. A |\n'
- ' | | precision of "0" is treated as equivalent '
- 'to a precision |\n'
- ' | | of "1". The precise rules are as follows: '
- 'suppose that |\n'
- ' | | the result formatted with presentation '
- 'type "\'e\'" and |\n'
- ' | | precision "p-1" would have exponent '
- '"exp". Then, if "m <= |\n'
- ' | | exp < p", where "m" is -4 for floats and '
- '-6 for |\n'
- ' | | "Decimals", the number is formatted with '
- 'presentation type |\n'
- ' | | "\'f\'" and precision "p-1-exp". '
- 'Otherwise, the number is |\n'
- ' | | formatted with presentation type "\'e\'" '
- 'and precision |\n'
- ' | | "p-1". In both cases insignificant '
- 'trailing zeros are |\n'
- ' | | removed from the significand, and the '
- 'decimal point is |\n'
- ' | | also removed if there are no remaining '
- 'digits following |\n'
- ' | | it, unless the "\'#\'" option is used. '
- 'With no precision |\n'
- ' | | given, uses a precision of "6" significant '
- 'digits for |\n'
- ' | | "float". For "Decimal", the coefficient of '
- 'the result is |\n'
- ' | | formed from the coefficient digits of the '
- 'value; |\n'
- ' | | scientific notation is used for values '
- 'smaller than "1e-6" |\n'
- ' | | in absolute value and values where the '
- 'place value of the |\n'
- ' | | least significant digit is larger than 1, '
- 'and fixed-point |\n'
- ' | | notation is used otherwise. Positive and '
- 'negative |\n'
- ' | | infinity, positive and negative zero, and '
- 'nans, are |\n'
- ' | | formatted as "inf", "-inf", "0", "-0" and '
- '"nan" |\n'
- ' | | respectively, regardless of the '
- 'precision. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'G\'" | General format. Same as "\'g\'" except '
- 'switches to "\'E\'" if |\n'
- ' | | the number gets too large. The '
- 'representations of infinity |\n'
- ' | | and NaN are uppercased, '
- 'too. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'n\'" | Number. This is the same as "\'g\'", '
- 'except that it uses the |\n'
- ' | | current locale setting to insert the '
- 'appropriate number |\n'
- ' | | separator '
- 'characters. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | "\'%\'" | Percentage. Multiplies the number by 100 '
- 'and displays in |\n'
- ' | | fixed ("\'f\'") format, followed by a '
- 'percent sign. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- ' | None | For "float" this is like the "\'g\'" type, '
- 'except that when |\n'
- ' | | fixed- point notation is used to format '
- 'the result, it |\n'
- ' | | always includes at least one digit past '
- 'the decimal point, |\n'
- ' | | and switches to the scientific notation '
- 'when "exp >= p - |\n'
- ' | | 1". When the precision is not specified, '
- 'the latter will |\n'
- ' | | be as large as needed to represent the '
- 'given value |\n'
- ' | | faithfully. For "Decimal", this is the '
- 'same as either |\n'
- ' | | "\'g\'" or "\'G\'" depending on the value '
- 'of |\n'
- ' | | "context.capitals" for the current decimal '
- 'context. The |\n'
- ' | | overall effect is to match the output of '
- '"str()" as |\n'
- ' | | altered by the other format '
- 'modifiers. |\n'
- ' '
- '+-----------+------------------------------------------------------------+\n'
- '\n'
- 'The result should be correctly rounded to a given precision '
- '"p" of\n'
- 'digits after the decimal point. The rounding mode for '
- '"float" matches\n'
- 'that of the "round()" builtin. For "Decimal", the rounding '
- 'mode of\n'
- 'the current context will be used.\n'
- '\n'
- 'The available presentation types for "complex" are the same '
- 'as those\n'
- 'for "float" ("\'%\'" is not allowed). Both the real and '
- 'imaginary\n'
- 'components of a complex number are formatted as '
- 'floating-point\n'
- 'numbers, according to the specified presentation type. '
- 'They are\n'
- 'separated by the mandatory sign of the imaginary part, the '
- 'latter\n'
- 'being terminated by a "j" suffix. If the presentation type '
- 'is\n'
- 'missing, the result will match the output of "str()" '
- '(complex numbers\n'
- 'with a non-zero real part are also surrounded by '
- 'parentheses),\n'
- 'possibly altered by other format modifiers.\n'
- '\n'
- '\n'
- 'Format examples\n'
- '===============\n'
- '\n'
- 'This section contains examples of the "str.format()" syntax '
- 'and\n'
- 'comparison with the old "%"-formatting.\n'
- '\n'
- 'In most of the cases the syntax is similar to the old '
- '"%"-formatting,\n'
- 'with the addition of the "{}" and with ":" used instead of '
- '"%". For\n'
- 'example, "\'%03.2f\'" can be translated to "\'{:03.2f}\'".\n'
- '\n'
- 'The new format syntax also supports new and different '
- 'options, shown\n'
- 'in the following examples.\n'
- '\n'
- 'Accessing arguments by position:\n'
- '\n'
- " >>> '{0}, {1}, {2}'.format('a', 'b', 'c')\n"
- " 'a, b, c'\n"
- " >>> '{}, {}, {}'.format('a', 'b', 'c') # 3.1+ only\n"
- " 'a, b, c'\n"
- " >>> '{2}, {1}, {0}'.format('a', 'b', 'c')\n"
- " 'c, b, a'\n"
- " >>> '{2}, {1}, {0}'.format(*'abc') # unpacking "
- 'argument sequence\n'
- " 'c, b, a'\n"
- " >>> '{0}{1}{0}'.format('abra', 'cad') # arguments' "
- 'indices can be repeated\n'
- " 'abracadabra'\n"
- '\n'
- 'Accessing arguments by name:\n'
- '\n'
- " >>> 'Coordinates: {latitude}, "
- "{longitude}'.format(latitude='37.24N', "
- "longitude='-115.81W')\n"
- " 'Coordinates: 37.24N, -115.81W'\n"
- " >>> coord = {'latitude': '37.24N', 'longitude': "
- "'-115.81W'}\n"
- " >>> 'Coordinates: {latitude}, "
- "{longitude}'.format(**coord)\n"
- " 'Coordinates: 37.24N, -115.81W'\n"
- '\n'
- 'Accessing arguments’ attributes:\n'
- '\n'
- ' >>> c = 3-5j\n'
- " >>> ('The complex number {0} is formed from the real "
- "part {0.real} '\n"
- " ... 'and the imaginary part {0.imag}.').format(c)\n"
- " 'The complex number (3-5j) is formed from the real part "
- "3.0 and the imaginary part -5.0.'\n"
- ' >>> class Point:\n'
- ' ... def __init__(self, x, y):\n'
- ' ... self.x, self.y = x, y\n'
- ' ... def __str__(self):\n'
- " ... return 'Point({self.x}, "
- "{self.y})'.format(self=self)\n"
- ' ...\n'
- ' >>> str(Point(4, 2))\n'
- " 'Point(4, 2)'\n"
- '\n'
- 'Accessing arguments’ items:\n'
- '\n'
- ' >>> coord = (3, 5)\n'
- " >>> 'X: {0[0]}; Y: {0[1]}'.format(coord)\n"
- " 'X: 3; Y: 5'\n"
- '\n'
- 'Replacing "%s" and "%r":\n'
- '\n'
- ' >>> "repr() shows quotes: {!r}; str() doesn\'t: '
- '{!s}".format(\'test1\', \'test2\')\n'
- ' "repr() shows quotes: \'test1\'; str() doesn\'t: test2"\n'
- '\n'
- 'Aligning the text and specifying a width:\n'
- '\n'
- " >>> '{:<30}'.format('left aligned')\n"
- " 'left aligned '\n"
- " >>> '{:>30}'.format('right aligned')\n"
- " ' right aligned'\n"
- " >>> '{:^30}'.format('centered')\n"
- " ' centered '\n"
- " >>> '{:*^30}'.format('centered') # use '*' as a fill "
- 'char\n'
- " '***********centered***********'\n"
- '\n'
- 'Replacing "%+f", "%-f", and "% f" and specifying a sign:\n'
- '\n'
- " >>> '{:+f}; {:+f}'.format(3.14, -3.14) # show it "
- 'always\n'
- " '+3.140000; -3.140000'\n"
- " >>> '{: f}; {: f}'.format(3.14, -3.14) # show a space "
- 'for positive numbers\n'
- " ' 3.140000; -3.140000'\n"
- " >>> '{:-f}; {:-f}'.format(3.14, -3.14) # show only the "
- "minus -- same as '{:f}; {:f}'\n"
- " '3.140000; -3.140000'\n"
- '\n'
- 'Replacing "%x" and "%o" and converting the value to '
- 'different bases:\n'
- '\n'
- ' >>> # format also supports binary numbers\n'
- ' >>> "int: {0:d}; hex: {0:x}; oct: {0:o}; bin: '
- '{0:b}".format(42)\n'
- " 'int: 42; hex: 2a; oct: 52; bin: 101010'\n"
- ' >>> # with 0x, 0o, or 0b as prefix:\n'
- ' >>> "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: '
- '{0:#b}".format(42)\n'
- " 'int: 42; hex: 0x2a; oct: 0o52; bin: 0b101010'\n"
- '\n'
- 'Using the comma as a thousands separator:\n'
- '\n'
- " >>> '{:,}'.format(1234567890)\n"
- " '1,234,567,890'\n"
- '\n'
- 'Expressing a percentage:\n'
- '\n'
- ' >>> points = 19\n'
- ' >>> total = 22\n'
- " >>> 'Correct answers: {:.2%}'.format(points/total)\n"
- " 'Correct answers: 86.36%'\n"
- '\n'
- 'Using type-specific formatting:\n'
- '\n'
- ' >>> import datetime\n'
- ' >>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)\n'
- " >>> '{:%Y-%m-%d %H:%M:%S}'.format(d)\n"
- " '2010-07-04 12:15:58'\n"
- '\n'
- 'Nesting arguments and more complex examples:\n'
- '\n'
- " >>> for align, text in zip('<^>', ['left', 'center', "
- "'right']):\n"
- " ... '{0:{fill}{align}16}'.format(text, fill=align, "
- 'align=align)\n'
- ' ...\n'
- " 'left<<<<<<<<<<<<'\n"
- " '^^^^^center^^^^^'\n"
- " '>>>>>>>>>>>right'\n"
- ' >>>\n'
- ' >>> octets = [192, 168, 0, 1]\n'
- " >>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets)\n"
- " 'C0A80001'\n"
- ' >>> int(_, 16)\n'
- ' 3232235521\n'
- ' >>>\n'
- ' >>> width = 5\n'
- ' >>> for num in range(5,12): \n'
- " ... for base in 'dXob':\n"
- " ... print('{0:{width}{base}}'.format(num, "
- "base=base, width=width), end=' ')\n"
- ' ... print()\n'
- ' ...\n'
- ' 5 5 5 101\n'
- ' 6 6 6 110\n'
- ' 7 7 7 111\n'
- ' 8 8 10 1000\n'
- ' 9 9 11 1001\n'
- ' 10 A 12 1010\n'
- ' 11 B 13 1011\n',
- 'function': 'Function definitions\n'
- '********************\n'
- '\n'
- 'A function definition defines a user-defined function object '
- '(see\n'
- 'section The standard type hierarchy):\n'
- '\n'
- ' funcdef ::= [decorators] "def" funcname '
- '[type_params] "(" [parameter_list] ")"\n'
- ' ["->" expression] ":" suite\n'
- ' decorators ::= decorator+\n'
- ' decorator ::= "@" assignment_expression '
- 'NEWLINE\n'
- ' parameter_list ::= defparameter ("," '
- 'defparameter)* "," "/" ["," [parameter_list_no_posonly]]\n'
- ' | parameter_list_no_posonly\n'
- ' parameter_list_no_posonly ::= defparameter ("," '
- 'defparameter)* ["," [parameter_list_starargs]]\n'
- ' | parameter_list_starargs\n'
- ' parameter_list_starargs ::= "*" [star_parameter] ("," '
- 'defparameter)* ["," [parameter_star_kwargs]]\n'
- ' "*" ("," defparameter)+ ["," '
- '[parameter_star_kwargs]]\n'
- ' | parameter_star_kwargs\n'
- ' parameter_star_kwargs ::= "**" parameter [","]\n'
- ' parameter ::= identifier [":" expression]\n'
- ' star_parameter ::= identifier [":" ["*"] '
- 'expression]\n'
- ' defparameter ::= parameter ["=" expression]\n'
- ' funcname ::= identifier\n'
- '\n'
- 'A function definition is an executable statement. Its execution '
- 'binds\n'
- 'the function name in the current local namespace to a function '
- 'object\n'
- '(a wrapper around the executable code for the function). This\n'
- 'function object contains a reference to the current global '
- 'namespace\n'
- 'as the global namespace to be used when the function is called.\n'
- '\n'
- 'The function definition does not execute the function body; this '
- 'gets\n'
- 'executed only when the function is called. [4]\n'
- '\n'
- 'A function definition may be wrapped by one or more *decorator*\n'
- 'expressions. Decorator expressions are evaluated when the '
- 'function is\n'
- 'defined, in the scope that contains the function definition. '
- 'The\n'
- 'result must be a callable, which is invoked with the function '
- 'object\n'
- 'as the only argument. The returned value is bound to the '
- 'function name\n'
- 'instead of the function object. Multiple decorators are applied '
- 'in\n'
- 'nested fashion. For example, the following code\n'
- '\n'
- ' @f1(arg)\n'
- ' @f2\n'
- ' def func(): pass\n'
- '\n'
- 'is roughly equivalent to\n'
- '\n'
- ' def func(): pass\n'
- ' func = f1(arg)(f2(func))\n'
- '\n'
- 'except that the original function is not temporarily bound to '
- 'the name\n'
- '"func".\n'
- '\n'
- 'Changed in version 3.9: Functions may be decorated with any '
- 'valid\n'
- '"assignment_expression". Previously, the grammar was much more\n'
- 'restrictive; see **PEP 614** for details.\n'
- '\n'
- 'A list of type parameters may be given in square brackets '
- 'between the\n'
- 'function’s name and the opening parenthesis for its parameter '
- 'list.\n'
- 'This indicates to static type checkers that the function is '
- 'generic.\n'
- 'At runtime, the type parameters can be retrieved from the '
- 'function’s\n'
- '"__type_params__" attribute. See Generic functions for more.\n'
- '\n'
- 'Changed in version 3.12: Type parameter lists are new in Python '
- '3.12.\n'
- '\n'
- 'When one or more *parameters* have the form *parameter* "="\n'
- '*expression*, the function is said to have “default parameter '
- 'values.”\n'
- 'For a parameter with a default value, the corresponding '
- '*argument* may\n'
- 'be omitted from a call, in which case the parameter’s default '
- 'value is\n'
- 'substituted. If a parameter has a default value, all following\n'
- 'parameters up until the “"*"” must also have a default value — '
- 'this is\n'
- 'a syntactic restriction that is not expressed by the grammar.\n'
- '\n'
- '**Default parameter values are evaluated from left to right when '
- 'the\n'
- 'function definition is executed.** This means that the '
- 'expression is\n'
- 'evaluated once, when the function is defined, and that the same '
- '“pre-\n'
- 'computed” value is used for each call. This is especially '
- 'important\n'
- 'to understand when a default parameter value is a mutable '
- 'object, such\n'
- 'as a list or a dictionary: if the function modifies the object '
- '(e.g.\n'
- 'by appending an item to a list), the default parameter value is '
- 'in\n'
- 'effect modified. This is generally not what was intended. A '
- 'way\n'
- 'around this is to use "None" as the default, and explicitly test '
- 'for\n'
- 'it in the body of the function, e.g.:\n'
- '\n'
- ' def whats_on_the_telly(penguin=None):\n'
- ' if penguin is None:\n'
- ' penguin = []\n'
- ' penguin.append("property of the zoo")\n'
- ' return penguin\n'
- '\n'
- 'Function call semantics are described in more detail in section '
- 'Calls.\n'
- 'A function call always assigns values to all parameters '
- 'mentioned in\n'
- 'the parameter list, either from positional arguments, from '
- 'keyword\n'
- 'arguments, or from default values. If the form “"*identifier"” '
- 'is\n'
- 'present, it is initialized to a tuple receiving any excess '
- 'positional\n'
- 'parameters, defaulting to the empty tuple. If the form\n'
- '“"**identifier"” is present, it is initialized to a new ordered\n'
- 'mapping receiving any excess keyword arguments, defaulting to a '
- 'new\n'
- 'empty mapping of the same type. Parameters after “"*"” or\n'
- '“"*identifier"” are keyword-only parameters and may only be '
- 'passed by\n'
- 'keyword arguments. Parameters before “"/"” are positional-only\n'
- 'parameters and may only be passed by positional arguments.\n'
- '\n'
- 'Changed in version 3.8: The "/" function parameter syntax may be '
- 'used\n'
- 'to indicate positional-only parameters. See **PEP 570** for '
- 'details.\n'
- '\n'
- 'Parameters may have an *annotation* of the form “": '
- 'expression"”\n'
- 'following the parameter name. Any parameter may have an '
- 'annotation,\n'
- 'even those of the form "*identifier" or "**identifier". (As a '
- 'special\n'
- 'case, parameters of the form "*identifier" may have an '
- 'annotation “":\n'
- '*expression"”.) Functions may have “return” annotation of the '
- 'form\n'
- '“"-> expression"” after the parameter list. These annotations '
- 'can be\n'
- 'any valid Python expression. The presence of annotations does '
- 'not\n'
- 'change the semantics of a function. The annotation values are\n'
- 'available as values of a dictionary keyed by the parameters’ '
- 'names in\n'
- 'the "__annotations__" attribute of the function object. If the\n'
- '"annotations" import from "__future__" is used, annotations are\n'
- 'preserved as strings at runtime which enables postponed '
- 'evaluation.\n'
- 'Otherwise, they are evaluated when the function definition is\n'
- 'executed. In this case annotations may be evaluated in a '
- 'different\n'
- 'order than they appear in the source code.\n'
- '\n'
- 'Changed in version 3.11: Parameters of the form “"*identifier"” '
- 'may\n'
- 'have an annotation “": *expression"”. See **PEP 646**.\n'
- '\n'
- 'It is also possible to create anonymous functions (functions not '
- 'bound\n'
- 'to a name), for immediate use in expressions. This uses lambda\n'
- 'expressions, described in section Lambdas. Note that the '
- 'lambda\n'
- 'expression is merely a shorthand for a simplified function '
- 'definition;\n'
- 'a function defined in a “"def"” statement can be passed around '
- 'or\n'
- 'assigned to another name just like a function defined by a '
- 'lambda\n'
- 'expression. The “"def"” form is actually more powerful since '
- 'it\n'
- 'allows the execution of multiple statements and annotations.\n'
- '\n'
- '**Programmer’s note:** Functions are first-class objects. A '
- '“"def"”\n'
- 'statement executed inside a function definition defines a local\n'
- 'function that can be returned or passed around. Free variables '
- 'used\n'
- 'in the nested function can access the local variables of the '
- 'function\n'
- 'containing the def. See section Naming and binding for '
- 'details.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 3107** - Function Annotations\n'
- ' The original specification for function annotations.\n'
- '\n'
- ' **PEP 484** - Type Hints\n'
- ' Definition of a standard meaning for annotations: type '
- 'hints.\n'
- '\n'
- ' **PEP 526** - Syntax for Variable Annotations\n'
- ' Ability to type hint variable declarations, including '
- 'class\n'
- ' variables and instance variables.\n'
- '\n'
- ' **PEP 563** - Postponed Evaluation of Annotations\n'
- ' Support for forward references within annotations by '
- 'preserving\n'
- ' annotations in a string form at runtime instead of eager\n'
- ' evaluation.\n'
- '\n'
- ' **PEP 318** - Decorators for Functions and Methods\n'
- ' Function and method decorators were introduced. Class '
- 'decorators\n'
- ' were introduced in **PEP 3129**.\n',
- 'global': 'The "global" statement\n'
- '**********************\n'
- '\n'
- ' global_stmt ::= "global" identifier ("," identifier)*\n'
- '\n'
- 'The "global" statement causes the listed identifiers to be '
- 'interpreted\n'
- 'as globals. It would be impossible to assign to a global variable\n'
- 'without "global", although free variables may refer to globals '
- 'without\n'
- 'being declared global.\n'
- '\n'
- 'The "global" statement applies to the entire scope of a function '
- 'or\n'
- 'class body. A "SyntaxError" is raised if a variable is used or\n'
- 'assigned to prior to its global declaration in the scope.\n'
- '\n'
- '**Programmer’s note:** "global" is a directive to the parser. It\n'
- 'applies only to code parsed at the same time as the "global"\n'
- 'statement. In particular, a "global" statement contained in a '
- 'string\n'
- 'or code object supplied to the built-in "exec()" function does '
- 'not\n'
- 'affect the code block *containing* the function call, and code\n'
- 'contained in such a string is unaffected by "global" statements in '
- 'the\n'
- 'code containing the function call. The same applies to the '
- '"eval()"\n'
- 'and "compile()" functions.\n',
- 'id-classes': 'Reserved classes of identifiers\n'
- '*******************************\n'
- '\n'
- 'Certain classes of identifiers (besides keywords) have '
- 'special\n'
- 'meanings. These classes are identified by the patterns of '
- 'leading and\n'
- 'trailing underscore characters:\n'
- '\n'
- '"_*"\n'
- ' Not imported by "from module import *".\n'
- '\n'
- '"_"\n'
- ' In a "case" pattern within a "match" statement, "_" is a '
- 'soft\n'
- ' keyword that denotes a wildcard.\n'
- '\n'
- ' Separately, the interactive interpreter makes the result of '
- 'the\n'
- ' last evaluation available in the variable "_". (It is '
- 'stored in the\n'
- ' "builtins" module, alongside built-in functions like '
- '"print".)\n'
- '\n'
- ' Elsewhere, "_" is a regular identifier. It is often used to '
- 'name\n'
- ' “special” items, but it is not special to Python itself.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' The name "_" is often used in conjunction with\n'
- ' internationalization; refer to the documentation for the\n'
- ' "gettext" module for more information on this '
- 'convention.It is\n'
- ' also commonly used for unused variables.\n'
- '\n'
- '"__*__"\n'
- ' System-defined names, informally known as “dunder” names. '
- 'These\n'
- ' names are defined by the interpreter and its '
- 'implementation\n'
- ' (including the standard library). Current system names are\n'
- ' discussed in the Special method names section and '
- 'elsewhere. More\n'
- ' will likely be defined in future versions of Python. *Any* '
- 'use of\n'
- ' "__*__" names, in any context, that does not follow '
- 'explicitly\n'
- ' documented use, is subject to breakage without warning.\n'
- '\n'
- '"__*"\n'
- ' Class-private names. Names in this category, when used '
- 'within the\n'
- ' context of a class definition, are re-written to use a '
- 'mangled form\n'
- ' to help avoid name clashes between “private” attributes of '
- 'base and\n'
- ' derived classes. See section Identifiers (Names).\n',
- 'identifiers': 'Identifiers and keywords\n'
- '************************\n'
- '\n'
- 'Identifiers (also referred to as *names*) are described by '
- 'the\n'
- 'following lexical definitions.\n'
- '\n'
- 'The syntax of identifiers in Python is based on the Unicode '
- 'standard\n'
- 'annex UAX-31, with elaboration and changes as defined below; '
- 'see also\n'
- '**PEP 3131** for further details.\n'
- '\n'
- 'Within the ASCII range (U+0001..U+007F), the valid characters '
- 'for\n'
- 'identifiers include the uppercase and lowercase letters "A" '
- 'through\n'
- '"Z", the underscore "_" and, except for the first character, '
- 'the\n'
- 'digits "0" through "9". Python 3.0 introduced additional '
- 'characters\n'
- 'from outside the ASCII range (see **PEP 3131**). For these\n'
- 'characters, the classification uses the version of the '
- 'Unicode\n'
- 'Character Database as included in the "unicodedata" module.\n'
- '\n'
- 'Identifiers are unlimited in length. Case is significant.\n'
- '\n'
- ' identifier ::= xid_start xid_continue*\n'
- ' id_start ::= <all characters in general categories Lu, '
- 'Ll, Lt, Lm, Lo, Nl, the underscore, and characters with the '
- 'Other_ID_Start property>\n'
- ' id_continue ::= <all characters in id_start, plus '
- 'characters in the categories Mn, Mc, Nd, Pc and others with '
- 'the Other_ID_Continue property>\n'
- ' xid_start ::= <all characters in id_start whose NFKC '
- 'normalization is in "id_start xid_continue*">\n'
- ' xid_continue ::= <all characters in id_continue whose NFKC '
- 'normalization is in "id_continue*">\n'
- '\n'
- 'The Unicode category codes mentioned above stand for:\n'
- '\n'
- '* *Lu* - uppercase letters\n'
- '\n'
- '* *Ll* - lowercase letters\n'
- '\n'
- '* *Lt* - titlecase letters\n'
- '\n'
- '* *Lm* - modifier letters\n'
- '\n'
- '* *Lo* - other letters\n'
- '\n'
- '* *Nl* - letter numbers\n'
- '\n'
- '* *Mn* - nonspacing marks\n'
- '\n'
- '* *Mc* - spacing combining marks\n'
- '\n'
- '* *Nd* - decimal numbers\n'
- '\n'
- '* *Pc* - connector punctuations\n'
- '\n'
- '* *Other_ID_Start* - explicit list of characters in '
- 'PropList.txt to\n'
- ' support backwards compatibility\n'
- '\n'
- '* *Other_ID_Continue* - likewise\n'
- '\n'
- 'All identifiers are converted into the normal form NFKC while '
- 'parsing;\n'
- 'comparison of identifiers is based on NFKC.\n'
- '\n'
- 'A non-normative HTML file listing all valid identifier '
- 'characters for\n'
- 'Unicode 15.0.0 can be found at\n'
- 'https://www.unicode.org/Public/15.0.0/ucd/DerivedCoreProperties.txt\n'
- '\n'
- '\n'
- 'Keywords\n'
- '========\n'
- '\n'
- 'The following identifiers are used as reserved words, or '
- '*keywords* of\n'
- 'the language, and cannot be used as ordinary identifiers. '
- 'They must\n'
- 'be spelled exactly as written here:\n'
- '\n'
- ' False await else import pass\n'
- ' None break except in raise\n'
- ' True class finally is return\n'
- ' and continue for lambda try\n'
- ' as def from nonlocal while\n'
- ' assert del global not with\n'
- ' async elif if or yield\n'
- '\n'
- '\n'
- 'Soft Keywords\n'
- '=============\n'
- '\n'
- 'Added in version 3.10.\n'
- '\n'
- 'Some identifiers are only reserved under specific contexts. '
- 'These are\n'
- 'known as *soft keywords*. The identifiers "match", "case", '
- '"type" and\n'
- '"_" can syntactically act as keywords in certain contexts, '
- 'but this\n'
- 'distinction is done at the parser level, not when '
- 'tokenizing.\n'
- '\n'
- 'As soft keywords, their use in the grammar is possible while '
- 'still\n'
- 'preserving compatibility with existing code that uses these '
- 'names as\n'
- 'identifier names.\n'
- '\n'
- '"match", "case", and "_" are used in the "match" statement. '
- '"type" is\n'
- 'used in the "type" statement.\n'
- '\n'
- 'Changed in version 3.12: "type" is now a soft keyword.\n'
- '\n'
- '\n'
- 'Reserved classes of identifiers\n'
- '===============================\n'
- '\n'
- 'Certain classes of identifiers (besides keywords) have '
- 'special\n'
- 'meanings. These classes are identified by the patterns of '
- 'leading and\n'
- 'trailing underscore characters:\n'
- '\n'
- '"_*"\n'
- ' Not imported by "from module import *".\n'
- '\n'
- '"_"\n'
- ' In a "case" pattern within a "match" statement, "_" is a '
- 'soft\n'
- ' keyword that denotes a wildcard.\n'
- '\n'
- ' Separately, the interactive interpreter makes the result '
- 'of the\n'
- ' last evaluation available in the variable "_". (It is '
- 'stored in the\n'
- ' "builtins" module, alongside built-in functions like '
- '"print".)\n'
- '\n'
- ' Elsewhere, "_" is a regular identifier. It is often used '
- 'to name\n'
- ' “special” items, but it is not special to Python itself.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' The name "_" is often used in conjunction with\n'
- ' internationalization; refer to the documentation for '
- 'the\n'
- ' "gettext" module for more information on this '
- 'convention.It is\n'
- ' also commonly used for unused variables.\n'
- '\n'
- '"__*__"\n'
- ' System-defined names, informally known as “dunder” names. '
- 'These\n'
- ' names are defined by the interpreter and its '
- 'implementation\n'
- ' (including the standard library). Current system names '
- 'are\n'
- ' discussed in the Special method names section and '
- 'elsewhere. More\n'
- ' will likely be defined in future versions of Python. '
- '*Any* use of\n'
- ' "__*__" names, in any context, that does not follow '
- 'explicitly\n'
- ' documented use, is subject to breakage without warning.\n'
- '\n'
- '"__*"\n'
- ' Class-private names. Names in this category, when used '
- 'within the\n'
- ' context of a class definition, are re-written to use a '
- 'mangled form\n'
- ' to help avoid name clashes between “private” attributes of '
- 'base and\n'
- ' derived classes. See section Identifiers (Names).\n',
- 'if': 'The "if" statement\n'
- '******************\n'
- '\n'
- 'The "if" statement is used for conditional execution:\n'
- '\n'
- ' if_stmt ::= "if" assignment_expression ":" suite\n'
- ' ("elif" assignment_expression ":" suite)*\n'
- ' ["else" ":" suite]\n'
- '\n'
- 'It selects exactly one of the suites by evaluating the expressions '
- 'one\n'
- 'by one until one is found to be true (see section Boolean operations\n'
- 'for the definition of true and false); then that suite is executed\n'
- '(and no other part of the "if" statement is executed or evaluated).\n'
- 'If all expressions are false, the suite of the "else" clause, if\n'
- 'present, is executed.\n',
- 'imaginary': 'Imaginary literals\n'
- '******************\n'
- '\n'
- 'Imaginary literals are described by the following lexical '
- 'definitions:\n'
- '\n'
- ' imagnumber ::= (floatnumber | digitpart) ("j" | "J")\n'
- '\n'
- 'An imaginary literal yields a complex number with a real part '
- 'of 0.0.\n'
- 'Complex numbers are represented as a pair of floating-point '
- 'numbers\n'
- 'and have the same restrictions on their range. To create a '
- 'complex\n'
- 'number with a nonzero real part, add a floating-point number to '
- 'it,\n'
- 'e.g., "(3+4j)". Some examples of imaginary literals:\n'
- '\n'
- ' 3.14j 10.j 10j .001j 1e100j 3.14e-10j '
- '3.14_15_93j\n',
- 'import': 'The "import" statement\n'
- '**********************\n'
- '\n'
- ' import_stmt ::= "import" module ["as" identifier] ("," '
- 'module ["as" identifier])*\n'
- ' | "from" relative_module "import" identifier '
- '["as" identifier]\n'
- ' ("," identifier ["as" identifier])*\n'
- ' | "from" relative_module "import" "(" '
- 'identifier ["as" identifier]\n'
- ' ("," identifier ["as" identifier])* [","] ")"\n'
- ' | "from" relative_module "import" "*"\n'
- ' module ::= (identifier ".")* identifier\n'
- ' relative_module ::= "."* module | "."+\n'
- '\n'
- 'The basic import statement (no "from" clause) is executed in two\n'
- 'steps:\n'
- '\n'
- '1. find a module, loading and initializing it if necessary\n'
- '\n'
- '2. define a name or names in the local namespace for the scope '
- 'where\n'
- ' the "import" statement occurs.\n'
- '\n'
- 'When the statement contains multiple clauses (separated by commas) '
- 'the\n'
- 'two steps are carried out separately for each clause, just as '
- 'though\n'
- 'the clauses had been separated out into individual import '
- 'statements.\n'
- '\n'
- 'The details of the first step, finding and loading modules, are\n'
- 'described in greater detail in the section on the import system, '
- 'which\n'
- 'also describes the various types of packages and modules that can '
- 'be\n'
- 'imported, as well as all the hooks that can be used to customize '
- 'the\n'
- 'import system. Note that failures in this step may indicate '
- 'either\n'
- 'that the module could not be located, *or* that an error occurred\n'
- 'while initializing the module, which includes execution of the\n'
- 'module’s code.\n'
- '\n'
- 'If the requested module is retrieved successfully, it will be '
- 'made\n'
- 'available in the local namespace in one of three ways:\n'
- '\n'
- '* If the module name is followed by "as", then the name following '
- '"as"\n'
- ' is bound directly to the imported module.\n'
- '\n'
- '* If no other name is specified, and the module being imported is '
- 'a\n'
- ' top level module, the module’s name is bound in the local '
- 'namespace\n'
- ' as a reference to the imported module\n'
- '\n'
- '* If the module being imported is *not* a top level module, then '
- 'the\n'
- ' name of the top level package that contains the module is bound '
- 'in\n'
- ' the local namespace as a reference to the top level package. '
- 'The\n'
- ' imported module must be accessed using its full qualified name\n'
- ' rather than directly\n'
- '\n'
- 'The "from" form uses a slightly more complex process:\n'
- '\n'
- '1. find the module specified in the "from" clause, loading and\n'
- ' initializing it if necessary;\n'
- '\n'
- '2. for each of the identifiers specified in the "import" clauses:\n'
- '\n'
- ' 1. check if the imported module has an attribute by that name\n'
- '\n'
- ' 2. if not, attempt to import a submodule with that name and '
- 'then\n'
- ' check the imported module again for that attribute\n'
- '\n'
- ' 3. if the attribute is not found, "ImportError" is raised.\n'
- '\n'
- ' 4. otherwise, a reference to that value is stored in the local\n'
- ' namespace, using the name in the "as" clause if it is '
- 'present,\n'
- ' otherwise using the attribute name\n'
- '\n'
- 'Examples:\n'
- '\n'
- ' import foo # foo imported and bound locally\n'
- ' import foo.bar.baz # foo, foo.bar, and foo.bar.baz '
- 'imported, foo bound locally\n'
- ' import foo.bar.baz as fbb # foo, foo.bar, and foo.bar.baz '
- 'imported, foo.bar.baz bound as fbb\n'
- ' from foo.bar import baz # foo, foo.bar, and foo.bar.baz '
- 'imported, foo.bar.baz bound as baz\n'
- ' from foo import attr # foo imported and foo.attr bound as '
- 'attr\n'
- '\n'
- 'If the list of identifiers is replaced by a star ("\'*\'"), all '
- 'public\n'
- 'names defined in the module are bound in the local namespace for '
- 'the\n'
- 'scope where the "import" statement occurs.\n'
- '\n'
- 'The *public names* defined by a module are determined by checking '
- 'the\n'
- 'module’s namespace for a variable named "__all__"; if defined, it '
- 'must\n'
- 'be a sequence of strings which are names defined or imported by '
- 'that\n'
- 'module. The names given in "__all__" are all considered public '
- 'and\n'
- 'are required to exist. If "__all__" is not defined, the set of '
- 'public\n'
- 'names includes all names found in the module’s namespace which do '
- 'not\n'
- 'begin with an underscore character ("\'_\'"). "__all__" should '
- 'contain\n'
- 'the entire public API. It is intended to avoid accidentally '
- 'exporting\n'
- 'items that are not part of the API (such as library modules which '
- 'were\n'
- 'imported and used within the module).\n'
- '\n'
- 'The wild card form of import — "from module import *" — is only\n'
- 'allowed at the module level. Attempting to use it in class or\n'
- 'function definitions will raise a "SyntaxError".\n'
- '\n'
- 'When specifying what module to import you do not have to specify '
- 'the\n'
- 'absolute name of the module. When a module or package is '
- 'contained\n'
- 'within another package it is possible to make a relative import '
- 'within\n'
- 'the same top package without having to mention the package name. '
- 'By\n'
- 'using leading dots in the specified module or package after "from" '
- 'you\n'
- 'can specify how high to traverse up the current package hierarchy\n'
- 'without specifying exact names. One leading dot means the current\n'
- 'package where the module making the import exists. Two dots means '
- 'up\n'
- 'one package level. Three dots is up two levels, etc. So if you '
- 'execute\n'
- '"from . import mod" from a module in the "pkg" package then you '
- 'will\n'
- 'end up importing "pkg.mod". If you execute "from ..subpkg2 import '
- 'mod"\n'
- 'from within "pkg.subpkg1" you will import "pkg.subpkg2.mod". The\n'
- 'specification for relative imports is contained in the Package\n'
- 'Relative Imports section.\n'
- '\n'
- '"importlib.import_module()" is provided to support applications '
- 'that\n'
- 'determine dynamically the modules to be loaded.\n'
- '\n'
- 'Raises an auditing event "import" with arguments "module", '
- '"filename",\n'
- '"sys.path", "sys.meta_path", "sys.path_hooks".\n'
- '\n'
- '\n'
- 'Future statements\n'
- '=================\n'
- '\n'
- 'A *future statement* is a directive to the compiler that a '
- 'particular\n'
- 'module should be compiled using syntax or semantics that will be\n'
- 'available in a specified future release of Python where the '
- 'feature\n'
- 'becomes standard.\n'
- '\n'
- 'The future statement is intended to ease migration to future '
- 'versions\n'
- 'of Python that introduce incompatible changes to the language. '
- 'It\n'
- 'allows use of the new features on a per-module basis before the\n'
- 'release in which the feature becomes standard.\n'
- '\n'
- ' future_stmt ::= "from" "__future__" "import" feature ["as" '
- 'identifier]\n'
- ' ("," feature ["as" identifier])*\n'
- ' | "from" "__future__" "import" "(" feature '
- '["as" identifier]\n'
- ' ("," feature ["as" identifier])* [","] ")"\n'
- ' feature ::= identifier\n'
- '\n'
- 'A future statement must appear near the top of the module. The '
- 'only\n'
- 'lines that can appear before a future statement are:\n'
- '\n'
- '* the module docstring (if any),\n'
- '\n'
- '* comments,\n'
- '\n'
- '* blank lines, and\n'
- '\n'
- '* other future statements.\n'
- '\n'
- 'The only feature that requires using the future statement is\n'
- '"annotations" (see **PEP 563**).\n'
- '\n'
- 'All historical features enabled by the future statement are still\n'
- 'recognized by Python 3. The list includes "absolute_import",\n'
- '"division", "generators", "generator_stop", "unicode_literals",\n'
- '"print_function", "nested_scopes" and "with_statement". They are '
- 'all\n'
- 'redundant because they are always enabled, and only kept for '
- 'backwards\n'
- 'compatibility.\n'
- '\n'
- 'A future statement is recognized and treated specially at compile\n'
- 'time: Changes to the semantics of core constructs are often\n'
- 'implemented by generating different code. It may even be the '
- 'case\n'
- 'that a new feature introduces new incompatible syntax (such as a '
- 'new\n'
- 'reserved word), in which case the compiler may need to parse the\n'
- 'module differently. Such decisions cannot be pushed off until\n'
- 'runtime.\n'
- '\n'
- 'For any given release, the compiler knows which feature names '
- 'have\n'
- 'been defined, and raises a compile-time error if a future '
- 'statement\n'
- 'contains a feature not known to it.\n'
- '\n'
- 'The direct runtime semantics are the same as for any import '
- 'statement:\n'
- 'there is a standard module "__future__", described later, and it '
- 'will\n'
- 'be imported in the usual way at the time the future statement is\n'
- 'executed.\n'
- '\n'
- 'The interesting runtime semantics depend on the specific feature\n'
- 'enabled by the future statement.\n'
- '\n'
- 'Note that there is nothing special about the statement:\n'
- '\n'
- ' import __future__ [as name]\n'
- '\n'
- 'That is not a future statement; it’s an ordinary import statement '
- 'with\n'
- 'no special semantics or syntax restrictions.\n'
- '\n'
- 'Code compiled by calls to the built-in functions "exec()" and\n'
- '"compile()" that occur in a module "M" containing a future '
- 'statement\n'
- 'will, by default, use the new syntax or semantics associated with '
- 'the\n'
- 'future statement. This can be controlled by optional arguments '
- 'to\n'
- '"compile()" — see the documentation of that function for details.\n'
- '\n'
- 'A future statement typed at an interactive interpreter prompt '
- 'will\n'
- 'take effect for the rest of the interpreter session. If an\n'
- 'interpreter is started with the "-i" option, is passed a script '
- 'name\n'
- 'to execute, and the script includes a future statement, it will be '
- 'in\n'
- 'effect in the interactive session started after the script is\n'
- 'executed.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 236** - Back to the __future__\n'
- ' The original proposal for the __future__ mechanism.\n',
- 'in': 'Membership test operations\n'
- '**************************\n'
- '\n'
- 'The operators "in" and "not in" test for membership. "x in s"\n'
- 'evaluates to "True" if *x* is a member of *s*, and "False" otherwise.\n'
- '"x not in s" returns the negation of "x in s". All built-in '
- 'sequences\n'
- 'and set types support this as well as dictionary, for which "in" '
- 'tests\n'
- 'whether the dictionary has a given key. For container types such as\n'
- 'list, tuple, set, frozenset, dict, or collections.deque, the\n'
- 'expression "x in y" is equivalent to "any(x is e or x == e for e in\n'
- 'y)".\n'
- '\n'
- 'For the string and bytes types, "x in y" is "True" if and only if *x*\n'
- 'is a substring of *y*. An equivalent test is "y.find(x) != -1".\n'
- 'Empty strings are always considered to be a substring of any other\n'
- 'string, so """ in "abc"" will return "True".\n'
- '\n'
- 'For user-defined classes which define the "__contains__()" method, "x\n'
- 'in y" returns "True" if "y.__contains__(x)" returns a true value, and\n'
- '"False" otherwise.\n'
- '\n'
- 'For user-defined classes which do not define "__contains__()" but do\n'
- 'define "__iter__()", "x in y" is "True" if some value "z", for which\n'
- 'the expression "x is z or x == z" is true, is produced while '
- 'iterating\n'
- 'over "y". If an exception is raised during the iteration, it is as if\n'
- '"in" raised that exception.\n'
- '\n'
- 'Lastly, the old-style iteration protocol is tried: if a class defines\n'
- '"__getitem__()", "x in y" is "True" if and only if there is a non-\n'
- 'negative integer index *i* such that "x is y[i] or x == y[i]", and no\n'
- 'lower integer index raises the "IndexError" exception. (If any other\n'
- 'exception is raised, it is as if "in" raised that exception).\n'
- '\n'
- 'The operator "not in" is defined to have the inverse truth value of\n'
- '"in".\n',
- 'integers': 'Integer literals\n'
- '****************\n'
- '\n'
- 'Integer literals are described by the following lexical '
- 'definitions:\n'
- '\n'
- ' integer ::= decinteger | bininteger | octinteger | '
- 'hexinteger\n'
- ' decinteger ::= nonzerodigit (["_"] digit)* | "0"+ (["_"] '
- '"0")*\n'
- ' bininteger ::= "0" ("b" | "B") (["_"] bindigit)+\n'
- ' octinteger ::= "0" ("o" | "O") (["_"] octdigit)+\n'
- ' hexinteger ::= "0" ("x" | "X") (["_"] hexdigit)+\n'
- ' nonzerodigit ::= "1"..."9"\n'
- ' digit ::= "0"..."9"\n'
- ' bindigit ::= "0" | "1"\n'
- ' octdigit ::= "0"..."7"\n'
- ' hexdigit ::= digit | "a"..."f" | "A"..."F"\n'
- '\n'
- 'There is no limit for the length of integer literals apart from '
- 'what\n'
- 'can be stored in available memory.\n'
- '\n'
- 'Underscores are ignored for determining the numeric value of '
- 'the\n'
- 'literal. They can be used to group digits for enhanced '
- 'readability.\n'
- 'One underscore can occur between digits, and after base '
- 'specifiers\n'
- 'like "0x".\n'
- '\n'
- 'Note that leading zeros in a non-zero decimal number are not '
- 'allowed.\n'
- 'This is for disambiguation with C-style octal literals, which '
- 'Python\n'
- 'used before version 3.0.\n'
- '\n'
- 'Some examples of integer literals:\n'
- '\n'
- ' 7 2147483647 0o177 0b100110111\n'
- ' 3 79228162514264337593543950336 0o377 0xdeadbeef\n'
- ' 100_000_000_000 0b_1110_0101\n'
- '\n'
- 'Changed in version 3.6: Underscores are now allowed for '
- 'grouping\n'
- 'purposes in literals.\n',
- 'lambda': 'Lambdas\n'
- '*******\n'
- '\n'
- ' lambda_expr ::= "lambda" [parameter_list] ":" expression\n'
- '\n'
- 'Lambda expressions (sometimes called lambda forms) are used to '
- 'create\n'
- 'anonymous functions. The expression "lambda parameters: '
- 'expression"\n'
- 'yields a function object. The unnamed object behaves like a '
- 'function\n'
- 'object defined with:\n'
- '\n'
- ' def <lambda>(parameters):\n'
- ' return expression\n'
- '\n'
- 'See section Function definitions for the syntax of parameter '
- 'lists.\n'
- 'Note that functions created with lambda expressions cannot '
- 'contain\n'
- 'statements or annotations.\n',
- 'lists': 'List displays\n'
- '*************\n'
- '\n'
- 'A list display is a possibly empty series of expressions enclosed '
- 'in\n'
- 'square brackets:\n'
- '\n'
- ' list_display ::= "[" [flexible_expression_list | comprehension] '
- '"]"\n'
- '\n'
- 'A list display yields a new list object, the contents being '
- 'specified\n'
- 'by either a list of expressions or a comprehension. When a comma-\n'
- 'separated list of expressions is supplied, its elements are '
- 'evaluated\n'
- 'from left to right and placed into the list object in that order.\n'
- 'When a comprehension is supplied, the list is constructed from the\n'
- 'elements resulting from the comprehension.\n',
- 'naming': 'Naming and binding\n'
- '******************\n'
- '\n'
- '\n'
- 'Binding of names\n'
- '================\n'
- '\n'
- '*Names* refer to objects. Names are introduced by name binding\n'
- 'operations.\n'
- '\n'
- 'The following constructs bind names:\n'
- '\n'
- '* formal parameters to functions,\n'
- '\n'
- '* class definitions,\n'
- '\n'
- '* function definitions,\n'
- '\n'
- '* assignment expressions,\n'
- '\n'
- '* targets that are identifiers if occurring in an assignment:\n'
- '\n'
- ' * "for" loop header,\n'
- '\n'
- ' * after "as" in a "with" statement, "except" clause, "except*"\n'
- ' clause, or in the as-pattern in structural pattern matching,\n'
- '\n'
- ' * in a capture pattern in structural pattern matching\n'
- '\n'
- '* "import" statements.\n'
- '\n'
- '* "type" statements.\n'
- '\n'
- '* type parameter lists.\n'
- '\n'
- 'The "import" statement of the form "from ... import *" binds all '
- 'names\n'
- 'defined in the imported module, except those beginning with an\n'
- 'underscore. This form may only be used at the module level.\n'
- '\n'
- 'A target occurring in a "del" statement is also considered bound '
- 'for\n'
- 'this purpose (though the actual semantics are to unbind the '
- 'name).\n'
- '\n'
- 'Each assignment or import statement occurs within a block defined '
- 'by a\n'
- 'class or function definition or at the module level (the '
- 'top-level\n'
- 'code block).\n'
- '\n'
- 'If a name is bound in a block, it is a local variable of that '
- 'block,\n'
- 'unless declared as "nonlocal" or "global". If a name is bound at '
- 'the\n'
- 'module level, it is a global variable. (The variables of the '
- 'module\n'
- 'code block are local and global.) If a variable is used in a '
- 'code\n'
- 'block but not defined there, it is a *free variable*.\n'
- '\n'
- 'Each occurrence of a name in the program text refers to the '
- '*binding*\n'
- 'of that name established by the following name resolution rules.\n'
- '\n'
- '\n'
- 'Resolution of names\n'
- '===================\n'
- '\n'
- 'A *scope* defines the visibility of a name within a block. If a '
- 'local\n'
- 'variable is defined in a block, its scope includes that block. If '
- 'the\n'
- 'definition occurs in a function block, the scope extends to any '
- 'blocks\n'
- 'contained within the defining one, unless a contained block '
- 'introduces\n'
- 'a different binding for the name.\n'
- '\n'
- 'When a name is used in a code block, it is resolved using the '
- 'nearest\n'
- 'enclosing scope. The set of all such scopes visible to a code '
- 'block\n'
- 'is called the block’s *environment*.\n'
- '\n'
- 'When a name is not found at all, a "NameError" exception is '
- 'raised. If\n'
- 'the current scope is a function scope, and the name refers to a '
- 'local\n'
- 'variable that has not yet been bound to a value at the point where '
- 'the\n'
- 'name is used, an "UnboundLocalError" exception is raised.\n'
- '"UnboundLocalError" is a subclass of "NameError".\n'
- '\n'
- 'If a name binding operation occurs anywhere within a code block, '
- 'all\n'
- 'uses of the name within the block are treated as references to '
- 'the\n'
- 'current block. This can lead to errors when a name is used within '
- 'a\n'
- 'block before it is bound. This rule is subtle. Python lacks\n'
- 'declarations and allows name binding operations to occur anywhere\n'
- 'within a code block. The local variables of a code block can be\n'
- 'determined by scanning the entire text of the block for name '
- 'binding\n'
- 'operations. See the FAQ entry on UnboundLocalError for examples.\n'
- '\n'
- 'If the "global" statement occurs within a block, all uses of the '
- 'names\n'
- 'specified in the statement refer to the bindings of those names in '
- 'the\n'
- 'top-level namespace. Names are resolved in the top-level '
- 'namespace by\n'
- 'searching the global namespace, i.e. the namespace of the module\n'
- 'containing the code block, and the builtins namespace, the '
- 'namespace\n'
- 'of the module "builtins". The global namespace is searched '
- 'first. If\n'
- 'the names are not found there, the builtins namespace is searched\n'
- 'next. If the names are also not found in the builtins namespace, '
- 'new\n'
- 'variables are created in the global namespace. The global '
- 'statement\n'
- 'must precede all uses of the listed names.\n'
- '\n'
- 'The "global" statement has the same scope as a name binding '
- 'operation\n'
- 'in the same block. If the nearest enclosing scope for a free '
- 'variable\n'
- 'contains a global statement, the free variable is treated as a '
- 'global.\n'
- '\n'
- 'The "nonlocal" statement causes corresponding names to refer to\n'
- 'previously bound variables in the nearest enclosing function '
- 'scope.\n'
- '"SyntaxError" is raised at compile time if the given name does '
- 'not\n'
- 'exist in any enclosing function scope. Type parameters cannot be\n'
- 'rebound with the "nonlocal" statement.\n'
- '\n'
- 'The namespace for a module is automatically created the first time '
- 'a\n'
- 'module is imported. The main module for a script is always '
- 'called\n'
- '"__main__".\n'
- '\n'
- 'Class definition blocks and arguments to "exec()" and "eval()" '
- 'are\n'
- 'special in the context of name resolution. A class definition is '
- 'an\n'
- 'executable statement that may use and define names. These '
- 'references\n'
- 'follow the normal rules for name resolution with an exception '
- 'that\n'
- 'unbound local variables are looked up in the global namespace. '
- 'The\n'
- 'namespace of the class definition becomes the attribute dictionary '
- 'of\n'
- 'the class. The scope of names defined in a class block is limited '
- 'to\n'
- 'the class block; it does not extend to the code blocks of '
- 'methods.\n'
- 'This includes comprehensions and generator expressions, but it '
- 'does\n'
- 'not include annotation scopes, which have access to their '
- 'enclosing\n'
- 'class scopes. This means that the following will fail:\n'
- '\n'
- ' class A:\n'
- ' a = 42\n'
- ' b = list(a + i for i in range(10))\n'
- '\n'
- 'However, the following will succeed:\n'
- '\n'
- ' class A:\n'
- ' type Alias = Nested\n'
- ' class Nested: pass\n'
- '\n'
- " print(A.Alias.__value__) # <type 'A.Nested'>\n"
- '\n'
- '\n'
- 'Annotation scopes\n'
- '=================\n'
- '\n'
- 'Type parameter lists and "type" statements introduce *annotation\n'
- 'scopes*, which behave mostly like function scopes, but with some\n'
- 'exceptions discussed below. *Annotations* currently do not use\n'
- 'annotation scopes, but they are expected to use annotation scopes '
- 'in\n'
- 'Python 3.13 when **PEP 649** is implemented.\n'
- '\n'
- 'Annotation scopes are used in the following contexts:\n'
- '\n'
- '* Type parameter lists for generic type aliases.\n'
- '\n'
- '* Type parameter lists for generic functions. A generic '
- 'function’s\n'
- ' annotations are executed within the annotation scope, but its\n'
- ' defaults and decorators are not.\n'
- '\n'
- '* Type parameter lists for generic classes. A generic class’s '
- 'base\n'
- ' classes and keyword arguments are executed within the '
- 'annotation\n'
- ' scope, but its decorators are not.\n'
- '\n'
- '* The bounds and constraints for type variables (lazily '
- 'evaluated).\n'
- '\n'
- '* The value of type aliases (lazily evaluated).\n'
- '\n'
- 'Annotation scopes differ from function scopes in the following '
- 'ways:\n'
- '\n'
- '* Annotation scopes have access to their enclosing class '
- 'namespace. If\n'
- ' an annotation scope is immediately within a class scope, or '
- 'within\n'
- ' another annotation scope that is immediately within a class '
- 'scope,\n'
- ' the code in the annotation scope can use names defined in the '
- 'class\n'
- ' scope as if it were executed directly within the class body. '
- 'This\n'
- ' contrasts with regular functions defined within classes, which\n'
- ' cannot access names defined in the class scope.\n'
- '\n'
- '* Expressions in annotation scopes cannot contain "yield", "yield\n'
- ' from", "await", or ":=" expressions. (These expressions are '
- 'allowed\n'
- ' in other scopes contained within the annotation scope.)\n'
- '\n'
- '* Names defined in annotation scopes cannot be rebound with '
- '"nonlocal"\n'
- ' statements in inner scopes. This includes only type parameters, '
- 'as\n'
- ' no other syntactic elements that can appear within annotation '
- 'scopes\n'
- ' can introduce new names.\n'
- '\n'
- '* While annotation scopes have an internal name, that name is not\n'
- ' reflected in the *qualified name* of objects defined within the\n'
- ' scope. Instead, the "__qualname__" of such objects is as if the\n'
- ' object were defined in the enclosing scope.\n'
- '\n'
- 'Added in version 3.12: Annotation scopes were introduced in '
- 'Python\n'
- '3.12 as part of **PEP 695**.\n'
- '\n'
- '\n'
- 'Lazy evaluation\n'
- '===============\n'
- '\n'
- 'The values of type aliases created through the "type" statement '
- 'are\n'
- '*lazily evaluated*. The same applies to the bounds and constraints '
- 'of\n'
- 'type variables created through the type parameter syntax. This '
- 'means\n'
- 'that they are not evaluated when the type alias or type variable '
- 'is\n'
- 'created. Instead, they are only evaluated when doing so is '
- 'necessary\n'
- 'to resolve an attribute access.\n'
- '\n'
- 'Example:\n'
- '\n'
- ' >>> type Alias = 1/0\n'
- ' >>> Alias.__value__\n'
- ' Traceback (most recent call last):\n'
- ' ...\n'
- ' ZeroDivisionError: division by zero\n'
- ' >>> def func[T: 1/0](): pass\n'
- ' >>> T = func.__type_params__[0]\n'
- ' >>> T.__bound__\n'
- ' Traceback (most recent call last):\n'
- ' ...\n'
- ' ZeroDivisionError: division by zero\n'
- '\n'
- 'Here the exception is raised only when the "__value__" attribute '
- 'of\n'
- 'the type alias or the "__bound__" attribute of the type variable '
- 'is\n'
- 'accessed.\n'
- '\n'
- 'This behavior is primarily useful for references to types that '
- 'have\n'
- 'not yet been defined when the type alias or type variable is '
- 'created.\n'
- 'For example, lazy evaluation enables creation of mutually '
- 'recursive\n'
- 'type aliases:\n'
- '\n'
- ' from typing import Literal\n'
- '\n'
- ' type SimpleExpr = int | Parenthesized\n'
- ' type Parenthesized = tuple[Literal["("], Expr, Literal[")"]]\n'
- ' type Expr = SimpleExpr | tuple[SimpleExpr, Literal["+", "-"], '
- 'Expr]\n'
- '\n'
- 'Lazily evaluated values are evaluated in annotation scope, which '
- 'means\n'
- 'that names that appear inside the lazily evaluated value are '
- 'looked up\n'
- 'as if they were used in the immediately enclosing scope.\n'
- '\n'
- 'Added in version 3.12.\n'
- '\n'
- '\n'
- 'Builtins and restricted execution\n'
- '=================================\n'
- '\n'
- '**CPython implementation detail:** Users should not touch\n'
- '"__builtins__"; it is strictly an implementation detail. Users\n'
- 'wanting to override values in the builtins namespace should '
- '"import"\n'
- 'the "builtins" module and modify its attributes appropriately.\n'
- '\n'
- 'The builtins namespace associated with the execution of a code '
- 'block\n'
- 'is actually found by looking up the name "__builtins__" in its '
- 'global\n'
- 'namespace; this should be a dictionary or a module (in the latter '
- 'case\n'
- 'the module’s dictionary is used). By default, when in the '
- '"__main__"\n'
- 'module, "__builtins__" is the built-in module "builtins"; when in '
- 'any\n'
- 'other module, "__builtins__" is an alias for the dictionary of '
- 'the\n'
- '"builtins" module itself.\n'
- '\n'
- '\n'
- 'Interaction with dynamic features\n'
- '=================================\n'
- '\n'
- 'Name resolution of free variables occurs at runtime, not at '
- 'compile\n'
- 'time. This means that the following code will print 42:\n'
- '\n'
- ' i = 10\n'
- ' def f():\n'
- ' print(i)\n'
- ' i = 42\n'
- ' f()\n'
- '\n'
- 'The "eval()" and "exec()" functions do not have access to the '
- 'full\n'
- 'environment for resolving names. Names may be resolved in the '
- 'local\n'
- 'and global namespaces of the caller. Free variables are not '
- 'resolved\n'
- 'in the nearest enclosing namespace, but in the global namespace. '
- '[1]\n'
- 'The "exec()" and "eval()" functions have optional arguments to\n'
- 'override the global and local namespace. If only one namespace '
- 'is\n'
- 'specified, it is used for both.\n',
- 'nonlocal': 'The "nonlocal" statement\n'
- '************************\n'
- '\n'
- ' nonlocal_stmt ::= "nonlocal" identifier ("," identifier)*\n'
- '\n'
- 'When the definition of a function or class is nested (enclosed) '
- 'within\n'
- 'the definitions of other functions, its nonlocal scopes are the '
- 'local\n'
- 'scopes of the enclosing functions. The "nonlocal" statement '
- 'causes the\n'
- 'listed identifiers to refer to names previously bound in '
- 'nonlocal\n'
- 'scopes. It allows encapsulated code to rebind such nonlocal\n'
- 'identifiers. If a name is bound in more than one nonlocal '
- 'scope, the\n'
- 'nearest binding is used. If a name is not bound in any nonlocal '
- 'scope,\n'
- 'or if there is no nonlocal scope, a "SyntaxError" is raised.\n'
- '\n'
- 'The "nonlocal" statement applies to the entire scope of a '
- 'function or\n'
- 'class body. A "SyntaxError" is raised if a variable is used or\n'
- 'assigned to prior to its nonlocal declaration in the scope.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 3104** - Access to Names in Outer Scopes\n'
- ' The specification for the "nonlocal" statement.\n'
- '\n'
- '**Programmer’s note:** "nonlocal" is a directive to the parser '
- 'and\n'
- 'applies only to code parsed along with it. See the note for '
- 'the\n'
- '"global" statement.\n',
- 'numbers': 'Numeric literals\n'
- '****************\n'
- '\n'
- 'There are three types of numeric literals: integers, '
- 'floating-point\n'
- 'numbers, and imaginary numbers. There are no complex literals\n'
- '(complex numbers can be formed by adding a real number and an\n'
- 'imaginary number).\n'
- '\n'
- 'Note that numeric literals do not include a sign; a phrase like '
- '"-1"\n'
- 'is actually an expression composed of the unary operator ‘"-"’ '
- 'and the\n'
- 'literal "1".\n',
- 'numeric-types': 'Emulating numeric types\n'
- '***********************\n'
- '\n'
- 'The following methods can be defined to emulate numeric '
- 'objects.\n'
- 'Methods corresponding to operations that are not supported '
- 'by the\n'
- 'particular kind of number implemented (e.g., bitwise '
- 'operations for\n'
- 'non-integral numbers) should be left undefined.\n'
- '\n'
- 'object.__add__(self, other)\n'
- 'object.__sub__(self, other)\n'
- 'object.__mul__(self, other)\n'
- 'object.__matmul__(self, other)\n'
- 'object.__truediv__(self, other)\n'
- 'object.__floordiv__(self, other)\n'
- 'object.__mod__(self, other)\n'
- 'object.__divmod__(self, other)\n'
- 'object.__pow__(self, other[, modulo])\n'
- 'object.__lshift__(self, other)\n'
- 'object.__rshift__(self, other)\n'
- 'object.__and__(self, other)\n'
- 'object.__xor__(self, other)\n'
- 'object.__or__(self, other)\n'
- '\n'
- ' These methods are called to implement the binary '
- 'arithmetic\n'
- ' operations ("+", "-", "*", "@", "/", "//", "%", '
- '"divmod()",\n'
- ' "pow()", "**", "<<", ">>", "&", "^", "|"). For '
- 'instance, to\n'
- ' evaluate the expression "x + y", where *x* is an '
- 'instance of a\n'
- ' class that has an "__add__()" method, '
- '"type(x).__add__(x, y)" is\n'
- ' called. The "__divmod__()" method should be the '
- 'equivalent to\n'
- ' using "__floordiv__()" and "__mod__()"; it should not be '
- 'related to\n'
- ' "__truediv__()". Note that "__pow__()" should be '
- 'defined to accept\n'
- ' an optional third argument if the ternary version of the '
- 'built-in\n'
- ' "pow()" function is to be supported.\n'
- '\n'
- ' If one of those methods does not support the operation '
- 'with the\n'
- ' supplied arguments, it should return "NotImplemented".\n'
- '\n'
- 'object.__radd__(self, other)\n'
- 'object.__rsub__(self, other)\n'
- 'object.__rmul__(self, other)\n'
- 'object.__rmatmul__(self, other)\n'
- 'object.__rtruediv__(self, other)\n'
- 'object.__rfloordiv__(self, other)\n'
- 'object.__rmod__(self, other)\n'
- 'object.__rdivmod__(self, other)\n'
- 'object.__rpow__(self, other[, modulo])\n'
- 'object.__rlshift__(self, other)\n'
- 'object.__rrshift__(self, other)\n'
- 'object.__rand__(self, other)\n'
- 'object.__rxor__(self, other)\n'
- 'object.__ror__(self, other)\n'
- '\n'
- ' These methods are called to implement the binary '
- 'arithmetic\n'
- ' operations ("+", "-", "*", "@", "/", "//", "%", '
- '"divmod()",\n'
- ' "pow()", "**", "<<", ">>", "&", "^", "|") with reflected '
- '(swapped)\n'
- ' operands. These functions are only called if the left '
- 'operand does\n'
- ' not support the corresponding operation [3] and the '
- 'operands are of\n'
- ' different types. [4] For instance, to evaluate the '
- 'expression "x -\n'
- ' y", where *y* is an instance of a class that has an '
- '"__rsub__()"\n'
- ' method, "type(y).__rsub__(y, x)" is called if '
- '"type(x).__sub__(x,\n'
- ' y)" returns "NotImplemented".\n'
- '\n'
- ' Note that ternary "pow()" will not try calling '
- '"__rpow__()" (the\n'
- ' coercion rules would become too complicated).\n'
- '\n'
- ' Note:\n'
- '\n'
- ' If the right operand’s type is a subclass of the left '
- 'operand’s\n'
- ' type and that subclass provides a different '
- 'implementation of the\n'
- ' reflected method for the operation, this method will '
- 'be called\n'
- ' before the left operand’s non-reflected method. This '
- 'behavior\n'
- ' allows subclasses to override their ancestors’ '
- 'operations.\n'
- '\n'
- 'object.__iadd__(self, other)\n'
- 'object.__isub__(self, other)\n'
- 'object.__imul__(self, other)\n'
- 'object.__imatmul__(self, other)\n'
- 'object.__itruediv__(self, other)\n'
- 'object.__ifloordiv__(self, other)\n'
- 'object.__imod__(self, other)\n'
- 'object.__ipow__(self, other[, modulo])\n'
- 'object.__ilshift__(self, other)\n'
- 'object.__irshift__(self, other)\n'
- 'object.__iand__(self, other)\n'
- 'object.__ixor__(self, other)\n'
- 'object.__ior__(self, other)\n'
- '\n'
- ' These methods are called to implement the augmented '
- 'arithmetic\n'
- ' assignments ("+=", "-=", "*=", "@=", "/=", "//=", "%=", '
- '"**=",\n'
- ' "<<=", ">>=", "&=", "^=", "|="). These methods should '
- 'attempt to\n'
- ' do the operation in-place (modifying *self*) and return '
- 'the result\n'
- ' (which could be, but does not have to be, *self*). If a '
- 'specific\n'
- ' method is not defined, or if that method returns '
- '"NotImplemented",\n'
- ' the augmented assignment falls back to the normal '
- 'methods. For\n'
- ' instance, if *x* is an instance of a class with an '
- '"__iadd__()"\n'
- ' method, "x += y" is equivalent to "x = x.__iadd__(y)" . '
- 'If\n'
- ' "__iadd__()" does not exist, or if "x.__iadd__(y)" '
- 'returns\n'
- ' "NotImplemented", "x.__add__(y)" and "y.__radd__(x)" '
- 'are\n'
- ' considered, as with the evaluation of "x + y". In '
- 'certain\n'
- ' situations, augmented assignment can result in '
- 'unexpected errors\n'
- ' (see Why does a_tuple[i] += [‘item’] raise an exception '
- 'when the\n'
- ' addition works?), but this behavior is in fact part of '
- 'the data\n'
- ' model.\n'
- '\n'
- 'object.__neg__(self)\n'
- 'object.__pos__(self)\n'
- 'object.__abs__(self)\n'
- 'object.__invert__(self)\n'
- '\n'
- ' Called to implement the unary arithmetic operations '
- '("-", "+",\n'
- ' "abs()" and "~").\n'
- '\n'
- 'object.__complex__(self)\n'
- 'object.__int__(self)\n'
- 'object.__float__(self)\n'
- '\n'
- ' Called to implement the built-in functions "complex()", '
- '"int()" and\n'
- ' "float()". Should return a value of the appropriate '
- 'type.\n'
- '\n'
- 'object.__index__(self)\n'
- '\n'
- ' Called to implement "operator.index()", and whenever '
- 'Python needs\n'
- ' to losslessly convert the numeric object to an integer '
- 'object (such\n'
- ' as in slicing, or in the built-in "bin()", "hex()" and '
- '"oct()"\n'
- ' functions). Presence of this method indicates that the '
- 'numeric\n'
- ' object is an integer type. Must return an integer.\n'
- '\n'
- ' If "__int__()", "__float__()" and "__complex__()" are '
- 'not defined\n'
- ' then corresponding built-in functions "int()", "float()" '
- 'and\n'
- ' "complex()" fall back to "__index__()".\n'
- '\n'
- 'object.__round__(self[, ndigits])\n'
- 'object.__trunc__(self)\n'
- 'object.__floor__(self)\n'
- 'object.__ceil__(self)\n'
- '\n'
- ' Called to implement the built-in function "round()" and '
- '"math"\n'
- ' functions "trunc()", "floor()" and "ceil()". Unless '
- '*ndigits* is\n'
- ' passed to "__round__()" all these methods should return '
- 'the value\n'
- ' of the object truncated to an "Integral" (typically an '
- '"int").\n'
- '\n'
- ' The built-in function "int()" falls back to '
- '"__trunc__()" if\n'
- ' neither "__int__()" nor "__index__()" is defined.\n'
- '\n'
- ' Changed in version 3.11: The delegation of "int()" to '
- '"__trunc__()"\n'
- ' is deprecated.\n',
- 'objects': 'Objects, values and types\n'
- '*************************\n'
- '\n'
- '*Objects* are Python’s abstraction for data. All data in a '
- 'Python\n'
- 'program is represented by objects or by relations between '
- 'objects. (In\n'
- 'a sense, and in conformance to Von Neumann’s model of a “stored\n'
- 'program computer”, code is also represented by objects.)\n'
- '\n'
- 'Every object has an identity, a type and a value. An object’s\n'
- '*identity* never changes once it has been created; you may think '
- 'of it\n'
- 'as the object’s address in memory. The "is" operator compares '
- 'the\n'
- 'identity of two objects; the "id()" function returns an integer\n'
- 'representing its identity.\n'
- '\n'
- '**CPython implementation detail:** For CPython, "id(x)" is the '
- 'memory\n'
- 'address where "x" is stored.\n'
- '\n'
- 'An object’s type determines the operations that the object '
- 'supports\n'
- '(e.g., “does it have a length?”) and also defines the possible '
- 'values\n'
- 'for objects of that type. The "type()" function returns an '
- 'object’s\n'
- 'type (which is an object itself). Like its identity, an '
- 'object’s\n'
- '*type* is also unchangeable. [1]\n'
- '\n'
- 'The *value* of some objects can change. Objects whose value can\n'
- 'change are said to be *mutable*; objects whose value is '
- 'unchangeable\n'
- 'once they are created are called *immutable*. (The value of an\n'
- 'immutable container object that contains a reference to a '
- 'mutable\n'
- 'object can change when the latter’s value is changed; however '
- 'the\n'
- 'container is still considered immutable, because the collection '
- 'of\n'
- 'objects it contains cannot be changed. So, immutability is not\n'
- 'strictly the same as having an unchangeable value, it is more '
- 'subtle.)\n'
- 'An object’s mutability is determined by its type; for instance,\n'
- 'numbers, strings and tuples are immutable, while dictionaries '
- 'and\n'
- 'lists are mutable.\n'
- '\n'
- 'Objects are never explicitly destroyed; however, when they '
- 'become\n'
- 'unreachable they may be garbage-collected. An implementation is\n'
- 'allowed to postpone garbage collection or omit it altogether — it '
- 'is a\n'
- 'matter of implementation quality how garbage collection is\n'
- 'implemented, as long as no objects are collected that are still\n'
- 'reachable.\n'
- '\n'
- '**CPython implementation detail:** CPython currently uses a '
- 'reference-\n'
- 'counting scheme with (optional) delayed detection of cyclically '
- 'linked\n'
- 'garbage, which collects most objects as soon as they become\n'
- 'unreachable, but is not guaranteed to collect garbage containing\n'
- 'circular references. See the documentation of the "gc" module '
- 'for\n'
- 'information on controlling the collection of cyclic garbage. '
- 'Other\n'
- 'implementations act differently and CPython may change. Do not '
- 'depend\n'
- 'on immediate finalization of objects when they become unreachable '
- '(so\n'
- 'you should always close files explicitly).\n'
- '\n'
- 'Note that the use of the implementation’s tracing or debugging\n'
- 'facilities may keep objects alive that would normally be '
- 'collectable.\n'
- 'Also note that catching an exception with a "try"…"except" '
- 'statement\n'
- 'may keep objects alive.\n'
- '\n'
- 'Some objects contain references to “external” resources such as '
- 'open\n'
- 'files or windows. It is understood that these resources are '
- 'freed\n'
- 'when the object is garbage-collected, but since garbage '
- 'collection is\n'
- 'not guaranteed to happen, such objects also provide an explicit '
- 'way to\n'
- 'release the external resource, usually a "close()" method. '
- 'Programs\n'
- 'are strongly recommended to explicitly close such objects. The\n'
- '"try"…"finally" statement and the "with" statement provide '
- 'convenient\n'
- 'ways to do this.\n'
- '\n'
- 'Some objects contain references to other objects; these are '
- 'called\n'
- '*containers*. Examples of containers are tuples, lists and\n'
- 'dictionaries. The references are part of a container’s value. '
- 'In\n'
- 'most cases, when we talk about the value of a container, we imply '
- 'the\n'
- 'values, not the identities of the contained objects; however, '
- 'when we\n'
- 'talk about the mutability of a container, only the identities of '
- 'the\n'
- 'immediately contained objects are implied. So, if an immutable\n'
- 'container (like a tuple) contains a reference to a mutable '
- 'object, its\n'
- 'value changes if that mutable object is changed.\n'
- '\n'
- 'Types affect almost all aspects of object behavior. Even the\n'
- 'importance of object identity is affected in some sense: for '
- 'immutable\n'
- 'types, operations that compute new values may actually return a\n'
- 'reference to any existing object with the same type and value, '
- 'while\n'
- 'for mutable objects this is not allowed. For example, after "a = '
- '1; b\n'
- '= 1", *a* and *b* may or may not refer to the same object with '
- 'the\n'
- 'value one, depending on the implementation. This is because "int" '
- 'is\n'
- 'an immutable type, so the reference to "1" can be reused. This\n'
- 'behaviour depends on the implementation used, so should not be '
- 'relied\n'
- 'upon, but is something to be aware of when making use of object\n'
- 'identity tests. However, after "c = []; d = []", *c* and *d* are\n'
- 'guaranteed to refer to two different, unique, newly created '
- 'empty\n'
- 'lists. (Note that "e = f = []" assigns the *same* object to both '
- '*e*\n'
- 'and *f*.)\n',
- 'operator-summary': 'Operator precedence\n'
- '*******************\n'
- '\n'
- 'The following table summarizes the operator precedence '
- 'in Python, from\n'
- 'highest precedence (most binding) to lowest precedence '
- '(least\n'
- 'binding). Operators in the same box have the same '
- 'precedence. Unless\n'
- 'the syntax is explicitly given, operators are binary. '
- 'Operators in\n'
- 'the same box group left to right (except for '
- 'exponentiation and\n'
- 'conditional expressions, which group from right to '
- 'left).\n'
- '\n'
- 'Note that comparisons, membership tests, and identity '
- 'tests, all have\n'
- 'the same precedence and have a left-to-right chaining '
- 'feature as\n'
- 'described in the Comparisons section.\n'
- '\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| Operator | '
- 'Description |\n'
- '|=================================================|=======================================|\n'
- '| "(expressions...)", "[expressions...]", "{key: | '
- 'Binding or parenthesized expression, |\n'
- '| value...}", "{expressions...}" | list '
- 'display, dictionary display, set |\n'
- '| | '
- 'display |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "x[index]", "x[index:index]", | '
- 'Subscription, slicing, call, |\n'
- '| "x(arguments...)", "x.attribute" | '
- 'attribute reference |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "await x" | '
- 'Await expression |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "**" | '
- 'Exponentiation [5] |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "+x", "-x", "~x" | '
- 'Positive, negative, bitwise NOT |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "*", "@", "/", "//", "%" | '
- 'Multiplication, matrix |\n'
- '| | '
- 'multiplication, division, floor |\n'
- '| | '
- 'division, remainder [6] |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "+", "-" | '
- 'Addition and subtraction |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "<<", ">>" | '
- 'Shifts |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "&" | '
- 'Bitwise AND |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "^" | '
- 'Bitwise XOR |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "|" | '
- 'Bitwise OR |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "in", "not in", "is", "is not", "<", "<=", ">", | '
- 'Comparisons, including membership |\n'
- '| ">=", "!=", "==" | '
- 'tests and identity tests |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "not x" | '
- 'Boolean NOT |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "and" | '
- 'Boolean AND |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "or" | '
- 'Boolean OR |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "if" – "else" | '
- 'Conditional expression |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| "lambda" | '
- 'Lambda expression |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '| ":=" | '
- 'Assignment expression |\n'
- '+-------------------------------------------------+---------------------------------------+\n'
- '\n'
- '-[ Footnotes ]-\n'
- '\n'
- '[1] While "abs(x%y) < abs(y)" is true mathematically, '
- 'for floats it\n'
- ' may not be true numerically due to roundoff. For '
- 'example, and\n'
- ' assuming a platform on which a Python float is an '
- 'IEEE 754 double-\n'
- ' precision number, in order that "-1e-100 % 1e100" '
- 'have the same\n'
- ' sign as "1e100", the computed result is "-1e-100 + '
- '1e100", which\n'
- ' is numerically exactly equal to "1e100". The '
- 'function\n'
- ' "math.fmod()" returns a result whose sign matches '
- 'the sign of the\n'
- ' first argument instead, and so returns "-1e-100" in '
- 'this case.\n'
- ' Which approach is more appropriate depends on the '
- 'application.\n'
- '\n'
- '[2] If x is very close to an exact integer multiple of '
- 'y, it’s\n'
- ' possible for "x//y" to be one larger than '
- '"(x-x%y)//y" due to\n'
- ' rounding. In such cases, Python returns the latter '
- 'result, in\n'
- ' order to preserve that "divmod(x,y)[0] * y + x % y" '
- 'be very close\n'
- ' to "x".\n'
- '\n'
- '[3] The Unicode standard distinguishes between *code '
- 'points* (e.g.\n'
- ' U+0041) and *abstract characters* (e.g. “LATIN '
- 'CAPITAL LETTER A”).\n'
- ' While most abstract characters in Unicode are only '
- 'represented\n'
- ' using one code point, there is a number of abstract '
- 'characters\n'
- ' that can in addition be represented using a sequence '
- 'of more than\n'
- ' one code point. For example, the abstract character '
- '“LATIN\n'
- ' CAPITAL LETTER C WITH CEDILLA” can be represented as '
- 'a single\n'
- ' *precomposed character* at code position U+00C7, or '
- 'as a sequence\n'
- ' of a *base character* at code position U+0043 (LATIN '
- 'CAPITAL\n'
- ' LETTER C), followed by a *combining character* at '
- 'code position\n'
- ' U+0327 (COMBINING CEDILLA).\n'
- '\n'
- ' The comparison operators on strings compare at the '
- 'level of\n'
- ' Unicode code points. This may be counter-intuitive '
- 'to humans. For\n'
- ' example, ""\\u00C7" == "\\u0043\\u0327"" is "False", '
- 'even though both\n'
- ' strings represent the same abstract character “LATIN '
- 'CAPITAL\n'
- ' LETTER C WITH CEDILLA”.\n'
- '\n'
- ' To compare strings at the level of abstract '
- 'characters (that is,\n'
- ' in a way intuitive to humans), use '
- '"unicodedata.normalize()".\n'
- '\n'
- '[4] Due to automatic garbage-collection, free lists, and '
- 'the dynamic\n'
- ' nature of descriptors, you may notice seemingly '
- 'unusual behaviour\n'
- ' in certain uses of the "is" operator, like those '
- 'involving\n'
- ' comparisons between instance methods, or constants. '
- 'Check their\n'
- ' documentation for more info.\n'
- '\n'
- '[5] The power operator "**" binds less tightly than an '
- 'arithmetic or\n'
- ' bitwise unary operator on its right, that is, '
- '"2**-1" is "0.5".\n'
- '\n'
- '[6] The "%" operator is also used for string formatting; '
- 'the same\n'
- ' precedence applies.\n',
- 'pass': 'The "pass" statement\n'
- '********************\n'
- '\n'
- ' pass_stmt ::= "pass"\n'
- '\n'
- '"pass" is a null operation — when it is executed, nothing happens. '
- 'It\n'
- 'is useful as a placeholder when a statement is required '
- 'syntactically,\n'
- 'but no code needs to be executed, for example:\n'
- '\n'
- ' def f(arg): pass # a function that does nothing (yet)\n'
- '\n'
- ' class C: pass # a class with no methods (yet)\n',
- 'power': 'The power operator\n'
- '******************\n'
- '\n'
- 'The power operator binds more tightly than unary operators on its\n'
- 'left; it binds less tightly than unary operators on its right. '
- 'The\n'
- 'syntax is:\n'
- '\n'
- ' power ::= (await_expr | primary) ["**" u_expr]\n'
- '\n'
- 'Thus, in an unparenthesized sequence of power and unary operators, '
- 'the\n'
- 'operators are evaluated from right to left (this does not '
- 'constrain\n'
- 'the evaluation order for the operands): "-1**2" results in "-1".\n'
- '\n'
- 'The power operator has the same semantics as the built-in "pow()"\n'
- 'function, when called with two arguments: it yields its left '
- 'argument\n'
- 'raised to the power of its right argument. The numeric arguments '
- 'are\n'
- 'first converted to a common type, and the result is of that type.\n'
- '\n'
- 'For int operands, the result has the same type as the operands '
- 'unless\n'
- 'the second argument is negative; in that case, all arguments are\n'
- 'converted to float and a float result is delivered. For example,\n'
- '"10**2" returns "100", but "10**-2" returns "0.01".\n'
- '\n'
- 'Raising "0.0" to a negative power results in a '
- '"ZeroDivisionError".\n'
- 'Raising a negative number to a fractional power results in a '
- '"complex"\n'
- 'number. (In earlier versions it raised a "ValueError".)\n'
- '\n'
- 'This operation can be customized using the special "__pow__()" and\n'
- '"__rpow__()" methods.\n',
- 'raise': 'The "raise" statement\n'
- '*********************\n'
- '\n'
- ' raise_stmt ::= "raise" [expression ["from" expression]]\n'
- '\n'
- 'If no expressions are present, "raise" re-raises the exception that '
- 'is\n'
- 'currently being handled, which is also known as the *active\n'
- 'exception*. If there isn’t currently an active exception, a\n'
- '"RuntimeError" exception is raised indicating that this is an '
- 'error.\n'
- '\n'
- 'Otherwise, "raise" evaluates the first expression as the exception\n'
- 'object. It must be either a subclass or an instance of\n'
- '"BaseException". If it is a class, the exception instance will be\n'
- 'obtained when needed by instantiating the class with no arguments.\n'
- '\n'
- 'The *type* of the exception is the exception instance’s class, the\n'
- '*value* is the instance itself.\n'
- '\n'
- 'A traceback object is normally created automatically when an '
- 'exception\n'
- 'is raised and attached to it as the "__traceback__" attribute. You '
- 'can\n'
- 'create an exception and set your own traceback in one step using '
- 'the\n'
- '"with_traceback()" exception method (which returns the same '
- 'exception\n'
- 'instance, with its traceback set to its argument), like so:\n'
- '\n'
- ' raise Exception("foo occurred").with_traceback(tracebackobj)\n'
- '\n'
- 'The "from" clause is used for exception chaining: if given, the '
- 'second\n'
- '*expression* must be another exception class or instance. If the\n'
- 'second expression is an exception instance, it will be attached to '
- 'the\n'
- 'raised exception as the "__cause__" attribute (which is writable). '
- 'If\n'
- 'the expression is an exception class, the class will be '
- 'instantiated\n'
- 'and the resulting exception instance will be attached to the '
- 'raised\n'
- 'exception as the "__cause__" attribute. If the raised exception is '
- 'not\n'
- 'handled, both exceptions will be printed:\n'
- '\n'
- ' >>> try:\n'
- ' ... print(1 / 0)\n'
- ' ... except Exception as exc:\n'
- ' ... raise RuntimeError("Something bad happened") from exc\n'
- ' ...\n'
- ' Traceback (most recent call last):\n'
- ' File "<stdin>", line 2, in <module>\n'
- ' print(1 / 0)\n'
- ' ~~^~~\n'
- ' ZeroDivisionError: division by zero\n'
- '\n'
- ' The above exception was the direct cause of the following '
- 'exception:\n'
- '\n'
- ' Traceback (most recent call last):\n'
- ' File "<stdin>", line 4, in <module>\n'
- ' raise RuntimeError("Something bad happened") from exc\n'
- ' RuntimeError: Something bad happened\n'
- '\n'
- 'A similar mechanism works implicitly if a new exception is raised '
- 'when\n'
- 'an exception is already being handled. An exception may be '
- 'handled\n'
- 'when an "except" or "finally" clause, or a "with" statement, is '
- 'used.\n'
- 'The previous exception is then attached as the new exception’s\n'
- '"__context__" attribute:\n'
- '\n'
- ' >>> try:\n'
- ' ... print(1 / 0)\n'
- ' ... except:\n'
- ' ... raise RuntimeError("Something bad happened")\n'
- ' ...\n'
- ' Traceback (most recent call last):\n'
- ' File "<stdin>", line 2, in <module>\n'
- ' print(1 / 0)\n'
- ' ~~^~~\n'
- ' ZeroDivisionError: division by zero\n'
- '\n'
- ' During handling of the above exception, another exception '
- 'occurred:\n'
- '\n'
- ' Traceback (most recent call last):\n'
- ' File "<stdin>", line 4, in <module>\n'
- ' raise RuntimeError("Something bad happened")\n'
- ' RuntimeError: Something bad happened\n'
- '\n'
- 'Exception chaining can be explicitly suppressed by specifying '
- '"None"\n'
- 'in the "from" clause:\n'
- '\n'
- ' >>> try:\n'
- ' ... print(1 / 0)\n'
- ' ... except:\n'
- ' ... raise RuntimeError("Something bad happened") from None\n'
- ' ...\n'
- ' Traceback (most recent call last):\n'
- ' File "<stdin>", line 4, in <module>\n'
- ' RuntimeError: Something bad happened\n'
- '\n'
- 'Additional information on exceptions can be found in section\n'
- 'Exceptions, and information about handling exceptions is in '
- 'section\n'
- 'The try statement.\n'
- '\n'
- 'Changed in version 3.3: "None" is now permitted as "Y" in "raise X\n'
- 'from Y".Added the "__suppress_context__" attribute to suppress\n'
- 'automatic display of the exception context.\n'
- '\n'
- 'Changed in version 3.11: If the traceback of the active exception '
- 'is\n'
- 'modified in an "except" clause, a subsequent "raise" statement re-\n'
- 'raises the exception with the modified traceback. Previously, the\n'
- 'exception was re-raised with the traceback it had when it was '
- 'caught.\n',
- 'return': 'The "return" statement\n'
- '**********************\n'
- '\n'
- ' return_stmt ::= "return" [expression_list]\n'
- '\n'
- '"return" may only occur syntactically nested in a function '
- 'definition,\n'
- 'not within a nested class definition.\n'
- '\n'
- 'If an expression list is present, it is evaluated, else "None" is\n'
- 'substituted.\n'
- '\n'
- '"return" leaves the current function call with the expression list '
- '(or\n'
- '"None") as return value.\n'
- '\n'
- 'When "return" passes control out of a "try" statement with a '
- '"finally"\n'
- 'clause, that "finally" clause is executed before really leaving '
- 'the\n'
- 'function.\n'
- '\n'
- 'In a generator function, the "return" statement indicates that '
- 'the\n'
- 'generator is done and will cause "StopIteration" to be raised. '
- 'The\n'
- 'returned value (if any) is used as an argument to construct\n'
- '"StopIteration" and becomes the "StopIteration.value" attribute.\n'
- '\n'
- 'In an asynchronous generator function, an empty "return" '
- 'statement\n'
- 'indicates that the asynchronous generator is done and will cause\n'
- '"StopAsyncIteration" to be raised. A non-empty "return" statement '
- 'is\n'
- 'a syntax error in an asynchronous generator function.\n',
- 'sequence-types': 'Emulating container types\n'
- '*************************\n'
- '\n'
- 'The following methods can be defined to implement '
- 'container objects.\n'
- 'None of them are provided by the "object" class itself. '
- 'Containers\n'
- 'usually are *sequences* (such as "lists" or "tuples") or '
- '*mappings*\n'
- '(like *dictionaries*), but can represent other containers '
- 'as well.\n'
- 'The first set of methods is used either to emulate a '
- 'sequence or to\n'
- 'emulate a mapping; the difference is that for a sequence, '
- 'the\n'
- 'allowable keys should be the integers *k* for which "0 <= '
- 'k < N" where\n'
- '*N* is the length of the sequence, or "slice" objects, '
- 'which define a\n'
- 'range of items. It is also recommended that mappings '
- 'provide the\n'
- 'methods "keys()", "values()", "items()", "get()", '
- '"clear()",\n'
- '"setdefault()", "pop()", "popitem()", "copy()", and '
- '"update()"\n'
- 'behaving similar to those for Python’s standard '
- '"dictionary" objects.\n'
- 'The "collections.abc" module provides a "MutableMapping" '
- '*abstract\n'
- 'base class* to help create those methods from a base set '
- 'of\n'
- '"__getitem__()", "__setitem__()", "__delitem__()", and '
- '"keys()".\n'
- 'Mutable sequences should provide methods "append()", '
- '"count()",\n'
- '"index()", "extend()", "insert()", "pop()", "remove()", '
- '"reverse()"\n'
- 'and "sort()", like Python standard "list" objects. '
- 'Finally, sequence\n'
- 'types should implement addition (meaning concatenation) '
- 'and\n'
- 'multiplication (meaning repetition) by defining the '
- 'methods\n'
- '"__add__()", "__radd__()", "__iadd__()", "__mul__()", '
- '"__rmul__()" and\n'
- '"__imul__()" described below; they should not define other '
- 'numerical\n'
- 'operators. It is recommended that both mappings and '
- 'sequences\n'
- 'implement the "__contains__()" method to allow efficient '
- 'use of the\n'
- '"in" operator; for mappings, "in" should search the '
- 'mapping’s keys;\n'
- 'for sequences, it should search through the values. It is '
- 'further\n'
- 'recommended that both mappings and sequences implement '
- 'the\n'
- '"__iter__()" method to allow efficient iteration through '
- 'the\n'
- 'container; for mappings, "__iter__()" should iterate '
- 'through the\n'
- 'object’s keys; for sequences, it should iterate through '
- 'the values.\n'
- '\n'
- 'object.__len__(self)\n'
- '\n'
- ' Called to implement the built-in function "len()". '
- 'Should return\n'
- ' the length of the object, an integer ">=" 0. Also, an '
- 'object that\n'
- ' doesn’t define a "__bool__()" method and whose '
- '"__len__()" method\n'
- ' returns zero is considered to be false in a Boolean '
- 'context.\n'
- '\n'
- ' **CPython implementation detail:** In CPython, the '
- 'length is\n'
- ' required to be at most "sys.maxsize". If the length is '
- 'larger than\n'
- ' "sys.maxsize" some features (such as "len()") may '
- 'raise\n'
- ' "OverflowError". To prevent raising "OverflowError" by '
- 'truth value\n'
- ' testing, an object must define a "__bool__()" method.\n'
- '\n'
- 'object.__length_hint__(self)\n'
- '\n'
- ' Called to implement "operator.length_hint()". Should '
- 'return an\n'
- ' estimated length for the object (which may be greater '
- 'or less than\n'
- ' the actual length). The length must be an integer ">=" '
- '0. The\n'
- ' return value may also be "NotImplemented", which is '
- 'treated the\n'
- ' same as if the "__length_hint__" method didn’t exist at '
- 'all. This\n'
- ' method is purely an optimization and is never required '
- 'for\n'
- ' correctness.\n'
- '\n'
- ' Added in version 3.4.\n'
- '\n'
- 'Note:\n'
- '\n'
- ' Slicing is done exclusively with the following three '
- 'methods. A\n'
- ' call like\n'
- '\n'
- ' a[1:2] = b\n'
- '\n'
- ' is translated to\n'
- '\n'
- ' a[slice(1, 2, None)] = b\n'
- '\n'
- ' and so forth. Missing slice items are always filled in '
- 'with "None".\n'
- '\n'
- 'object.__getitem__(self, key)\n'
- '\n'
- ' Called to implement evaluation of "self[key]". For '
- '*sequence*\n'
- ' types, the accepted keys should be integers. '
- 'Optionally, they may\n'
- ' support "slice" objects as well. Negative index '
- 'support is also\n'
- ' optional. If *key* is of an inappropriate type, '
- '"TypeError" may be\n'
- ' raised; if *key* is a value outside the set of indexes '
- 'for the\n'
- ' sequence (after any special interpretation of negative '
- 'values),\n'
- ' "IndexError" should be raised. For *mapping* types, if '
- '*key* is\n'
- ' missing (not in the container), "KeyError" should be '
- 'raised.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' "for" loops expect that an "IndexError" will be '
- 'raised for\n'
- ' illegal indexes to allow proper detection of the end '
- 'of the\n'
- ' sequence.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' When subscripting a *class*, the special class '
- 'method\n'
- ' "__class_getitem__()" may be called instead of '
- '"__getitem__()".\n'
- ' See __class_getitem__ versus __getitem__ for more '
- 'details.\n'
- '\n'
- 'object.__setitem__(self, key, value)\n'
- '\n'
- ' Called to implement assignment to "self[key]". Same '
- 'note as for\n'
- ' "__getitem__()". This should only be implemented for '
- 'mappings if\n'
- ' the objects support changes to the values for keys, or '
- 'if new keys\n'
- ' can be added, or for sequences if elements can be '
- 'replaced. The\n'
- ' same exceptions should be raised for improper *key* '
- 'values as for\n'
- ' the "__getitem__()" method.\n'
- '\n'
- 'object.__delitem__(self, key)\n'
- '\n'
- ' Called to implement deletion of "self[key]". Same note '
- 'as for\n'
- ' "__getitem__()". This should only be implemented for '
- 'mappings if\n'
- ' the objects support removal of keys, or for sequences '
- 'if elements\n'
- ' can be removed from the sequence. The same exceptions '
- 'should be\n'
- ' raised for improper *key* values as for the '
- '"__getitem__()" method.\n'
- '\n'
- 'object.__missing__(self, key)\n'
- '\n'
- ' Called by "dict"."__getitem__()" to implement '
- '"self[key]" for dict\n'
- ' subclasses when key is not in the dictionary.\n'
- '\n'
- 'object.__iter__(self)\n'
- '\n'
- ' This method is called when an *iterator* is required '
- 'for a\n'
- ' container. This method should return a new iterator '
- 'object that can\n'
- ' iterate over all the objects in the container. For '
- 'mappings, it\n'
- ' should iterate over the keys of the container.\n'
- '\n'
- 'object.__reversed__(self)\n'
- '\n'
- ' Called (if present) by the "reversed()" built-in to '
- 'implement\n'
- ' reverse iteration. It should return a new iterator '
- 'object that\n'
- ' iterates over all the objects in the container in '
- 'reverse order.\n'
- '\n'
- ' If the "__reversed__()" method is not provided, the '
- '"reversed()"\n'
- ' built-in will fall back to using the sequence protocol '
- '("__len__()"\n'
- ' and "__getitem__()"). Objects that support the '
- 'sequence protocol\n'
- ' should only provide "__reversed__()" if they can '
- 'provide an\n'
- ' implementation that is more efficient than the one '
- 'provided by\n'
- ' "reversed()".\n'
- '\n'
- 'The membership test operators ("in" and "not in") are '
- 'normally\n'
- 'implemented as an iteration through a container. However, '
- 'container\n'
- 'objects can supply the following special method with a '
- 'more efficient\n'
- 'implementation, which also does not require the object be '
- 'iterable.\n'
- '\n'
- 'object.__contains__(self, item)\n'
- '\n'
- ' Called to implement membership test operators. Should '
- 'return true\n'
- ' if *item* is in *self*, false otherwise. For mapping '
- 'objects, this\n'
- ' should consider the keys of the mapping rather than the '
- 'values or\n'
- ' the key-item pairs.\n'
- '\n'
- ' For objects that don’t define "__contains__()", the '
- 'membership test\n'
- ' first tries iteration via "__iter__()", then the old '
- 'sequence\n'
- ' iteration protocol via "__getitem__()", see this '
- 'section in the\n'
- ' language reference.\n',
- 'shifting': 'Shifting operations\n'
- '*******************\n'
- '\n'
- 'The shifting operations have lower priority than the arithmetic\n'
- 'operations:\n'
- '\n'
- ' shift_expr ::= a_expr | shift_expr ("<<" | ">>") a_expr\n'
- '\n'
- 'These operators accept integers as arguments. They shift the '
- 'first\n'
- 'argument to the left or right by the number of bits given by '
- 'the\n'
- 'second argument.\n'
- '\n'
- 'The left shift operation can be customized using the special\n'
- '"__lshift__()" and "__rlshift__()" methods. The right shift '
- 'operation\n'
- 'can be customized using the special "__rshift__()" and '
- '"__rrshift__()"\n'
- 'methods.\n'
- '\n'
- 'A right shift by *n* bits is defined as floor division by '
- '"pow(2,n)".\n'
- 'A left shift by *n* bits is defined as multiplication with '
- '"pow(2,n)".\n',
- 'slicings': 'Slicings\n'
- '********\n'
- '\n'
- 'A slicing selects a range of items in a sequence object (e.g., '
- 'a\n'
- 'string, tuple or list). Slicings may be used as expressions or '
- 'as\n'
- 'targets in assignment or "del" statements. The syntax for a '
- 'slicing:\n'
- '\n'
- ' slicing ::= primary "[" slice_list "]"\n'
- ' slice_list ::= slice_item ("," slice_item)* [","]\n'
- ' slice_item ::= expression | proper_slice\n'
- ' proper_slice ::= [lower_bound] ":" [upper_bound] [ ":" '
- '[stride] ]\n'
- ' lower_bound ::= expression\n'
- ' upper_bound ::= expression\n'
- ' stride ::= expression\n'
- '\n'
- 'There is ambiguity in the formal syntax here: anything that '
- 'looks like\n'
- 'an expression list also looks like a slice list, so any '
- 'subscription\n'
- 'can be interpreted as a slicing. Rather than further '
- 'complicating the\n'
- 'syntax, this is disambiguated by defining that in this case the\n'
- 'interpretation as a subscription takes priority over the\n'
- 'interpretation as a slicing (this is the case if the slice list\n'
- 'contains no proper slice).\n'
- '\n'
- 'The semantics for a slicing are as follows. The primary is '
- 'indexed\n'
- '(using the same "__getitem__()" method as normal subscription) '
- 'with a\n'
- 'key that is constructed from the slice list, as follows. If the '
- 'slice\n'
- 'list contains at least one comma, the key is a tuple containing '
- 'the\n'
- 'conversion of the slice items; otherwise, the conversion of the '
- 'lone\n'
- 'slice item is the key. The conversion of a slice item that is '
- 'an\n'
- 'expression is that expression. The conversion of a proper slice '
- 'is a\n'
- 'slice object (see section The standard type hierarchy) whose '
- '"start",\n'
- '"stop" and "step" attributes are the values of the expressions '
- 'given\n'
- 'as lower bound, upper bound and stride, respectively, '
- 'substituting\n'
- '"None" for missing expressions.\n',
- 'specialattrs': 'Special Attributes\n'
- '******************\n'
- '\n'
- 'The implementation adds a few special read-only attributes '
- 'to several\n'
- 'object types, where they are relevant. Some of these are '
- 'not reported\n'
- 'by the "dir()" built-in function.\n'
- '\n'
- 'definition.__name__\n'
- '\n'
- ' The name of the class, function, method, descriptor, or '
- 'generator\n'
- ' instance.\n'
- '\n'
- 'definition.__qualname__\n'
- '\n'
- ' The *qualified name* of the class, function, method, '
- 'descriptor, or\n'
- ' generator instance.\n'
- '\n'
- ' Added in version 3.3.\n'
- '\n'
- 'definition.__module__\n'
- '\n'
- ' The name of the module in which a class or function was '
- 'defined.\n'
- '\n'
- 'definition.__doc__\n'
- '\n'
- ' The documentation string of a class or function, or '
- '"None" if\n'
- ' undefined.\n'
- '\n'
- 'definition.__type_params__\n'
- '\n'
- ' The type parameters of generic classes, functions, and '
- 'type\n'
- ' aliases. For classes and functions that are not generic, '
- 'this will\n'
- ' be an empty tuple.\n'
- '\n'
- ' Added in version 3.12.\n',
- 'specialnames': 'Special method names\n'
- '********************\n'
- '\n'
- 'A class can implement certain operations that are invoked by '
- 'special\n'
- 'syntax (such as arithmetic operations or subscripting and '
- 'slicing) by\n'
- 'defining methods with special names. This is Python’s '
- 'approach to\n'
- '*operator overloading*, allowing classes to define their own '
- 'behavior\n'
- 'with respect to language operators. For instance, if a '
- 'class defines\n'
- 'a method named "__getitem__()", and "x" is an instance of '
- 'this class,\n'
- 'then "x[i]" is roughly equivalent to "type(x).__getitem__(x, '
- 'i)".\n'
- 'Except where mentioned, attempts to execute an operation '
- 'raise an\n'
- 'exception when no appropriate method is defined (typically\n'
- '"AttributeError" or "TypeError").\n'
- '\n'
- 'Setting a special method to "None" indicates that the '
- 'corresponding\n'
- 'operation is not available. For example, if a class sets '
- '"__iter__()"\n'
- 'to "None", the class is not iterable, so calling "iter()" on '
- 'its\n'
- 'instances will raise a "TypeError" (without falling back to\n'
- '"__getitem__()"). [2]\n'
- '\n'
- 'When implementing a class that emulates any built-in type, '
- 'it is\n'
- 'important that the emulation only be implemented to the '
- 'degree that it\n'
- 'makes sense for the object being modelled. For example, '
- 'some\n'
- 'sequences may work well with retrieval of individual '
- 'elements, but\n'
- 'extracting a slice may not make sense. (One example of this '
- 'is the\n'
- '"NodeList" interface in the W3C’s Document Object Model.)\n'
- '\n'
- '\n'
- 'Basic customization\n'
- '===================\n'
- '\n'
- 'object.__new__(cls[, ...])\n'
- '\n'
- ' Called to create a new instance of class *cls*. '
- '"__new__()" is a\n'
- ' static method (special-cased so you need not declare it '
- 'as such)\n'
- ' that takes the class of which an instance was requested '
- 'as its\n'
- ' first argument. The remaining arguments are those passed '
- 'to the\n'
- ' object constructor expression (the call to the class). '
- 'The return\n'
- ' value of "__new__()" should be the new object instance '
- '(usually an\n'
- ' instance of *cls*).\n'
- '\n'
- ' Typical implementations create a new instance of the '
- 'class by\n'
- ' invoking the superclass’s "__new__()" method using\n'
- ' "super().__new__(cls[, ...])" with appropriate arguments '
- 'and then\n'
- ' modifying the newly created instance as necessary before '
- 'returning\n'
- ' it.\n'
- '\n'
- ' If "__new__()" is invoked during object construction and '
- 'it returns\n'
- ' an instance of *cls*, then the new instance’s '
- '"__init__()" method\n'
- ' will be invoked like "__init__(self[, ...])", where '
- '*self* is the\n'
- ' new instance and the remaining arguments are the same as '
- 'were\n'
- ' passed to the object constructor.\n'
- '\n'
- ' If "__new__()" does not return an instance of *cls*, then '
- 'the new\n'
- ' instance’s "__init__()" method will not be invoked.\n'
- '\n'
- ' "__new__()" is intended mainly to allow subclasses of '
- 'immutable\n'
- ' types (like int, str, or tuple) to customize instance '
- 'creation. It\n'
- ' is also commonly overridden in custom metaclasses in '
- 'order to\n'
- ' customize class creation.\n'
- '\n'
- 'object.__init__(self[, ...])\n'
- '\n'
- ' Called after the instance has been created (by '
- '"__new__()"), but\n'
- ' before it is returned to the caller. The arguments are '
- 'those\n'
- ' passed to the class constructor expression. If a base '
- 'class has an\n'
- ' "__init__()" method, the derived class’s "__init__()" '
- 'method, if\n'
- ' any, must explicitly call it to ensure proper '
- 'initialization of the\n'
- ' base class part of the instance; for example:\n'
- ' "super().__init__([args...])".\n'
- '\n'
- ' Because "__new__()" and "__init__()" work together in '
- 'constructing\n'
- ' objects ("__new__()" to create it, and "__init__()" to '
- 'customize\n'
- ' it), no non-"None" value may be returned by "__init__()"; '
- 'doing so\n'
- ' will cause a "TypeError" to be raised at runtime.\n'
- '\n'
- 'object.__del__(self)\n'
- '\n'
- ' Called when the instance is about to be destroyed. This '
- 'is also\n'
- ' called a finalizer or (improperly) a destructor. If a '
- 'base class\n'
- ' has a "__del__()" method, the derived class’s "__del__()" '
- 'method,\n'
- ' if any, must explicitly call it to ensure proper deletion '
- 'of the\n'
- ' base class part of the instance.\n'
- '\n'
- ' It is possible (though not recommended!) for the '
- '"__del__()" method\n'
- ' to postpone destruction of the instance by creating a new '
- 'reference\n'
- ' to it. This is called object *resurrection*. It is\n'
- ' implementation-dependent whether "__del__()" is called a '
- 'second\n'
- ' time when a resurrected object is about to be destroyed; '
- 'the\n'
- ' current *CPython* implementation only calls it once.\n'
- '\n'
- ' It is not guaranteed that "__del__()" methods are called '
- 'for\n'
- ' objects that still exist when the interpreter exits.\n'
- ' "weakref.finalize" provides a straightforward way to '
- 'register a\n'
- ' cleanup function to be called when an object is garbage '
- 'collected.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' "del x" doesn’t directly call "x.__del__()" — the '
- 'former\n'
- ' decrements the reference count for "x" by one, and the '
- 'latter is\n'
- ' only called when "x"’s reference count reaches zero.\n'
- '\n'
- ' **CPython implementation detail:** It is possible for a '
- 'reference\n'
- ' cycle to prevent the reference count of an object from '
- 'going to\n'
- ' zero. In this case, the cycle will be later detected and '
- 'deleted\n'
- ' by the *cyclic garbage collector*. A common cause of '
- 'reference\n'
- ' cycles is when an exception has been caught in a local '
- 'variable.\n'
- ' The frame’s locals then reference the exception, which '
- 'references\n'
- ' its own traceback, which references the locals of all '
- 'frames caught\n'
- ' in the traceback.\n'
- '\n'
- ' See also: Documentation for the "gc" module.\n'
- '\n'
- ' Warning:\n'
- '\n'
- ' Due to the precarious circumstances under which '
- '"__del__()"\n'
- ' methods are invoked, exceptions that occur during their '
- 'execution\n'
- ' are ignored, and a warning is printed to "sys.stderr" '
- 'instead.\n'
- ' In particular:\n'
- '\n'
- ' * "__del__()" can be invoked when arbitrary code is '
- 'being\n'
- ' executed, including from any arbitrary thread. If '
- '"__del__()"\n'
- ' needs to take a lock or invoke any other blocking '
- 'resource, it\n'
- ' may deadlock as the resource may already be taken by '
- 'the code\n'
- ' that gets interrupted to execute "__del__()".\n'
- '\n'
- ' * "__del__()" can be executed during interpreter '
- 'shutdown. As a\n'
- ' consequence, the global variables it needs to access '
- '(including\n'
- ' other modules) may already have been deleted or set '
- 'to "None".\n'
- ' Python guarantees that globals whose name begins with '
- 'a single\n'
- ' underscore are deleted from their module before other '
- 'globals\n'
- ' are deleted; if no other references to such globals '
- 'exist, this\n'
- ' may help in assuring that imported modules are still '
- 'available\n'
- ' at the time when the "__del__()" method is called.\n'
- '\n'
- 'object.__repr__(self)\n'
- '\n'
- ' Called by the "repr()" built-in function to compute the '
- '“official”\n'
- ' string representation of an object. If at all possible, '
- 'this\n'
- ' should look like a valid Python expression that could be '
- 'used to\n'
- ' recreate an object with the same value (given an '
- 'appropriate\n'
- ' environment). If this is not possible, a string of the '
- 'form\n'
- ' "<...some useful description...>" should be returned. The '
- 'return\n'
- ' value must be a string object. If a class defines '
- '"__repr__()" but\n'
- ' not "__str__()", then "__repr__()" is also used when an '
- '“informal”\n'
- ' string representation of instances of that class is '
- 'required.\n'
- '\n'
- ' This is typically used for debugging, so it is important '
- 'that the\n'
- ' representation is information-rich and unambiguous. A '
- 'default\n'
- ' implementation is provided by the "object" class itself.\n'
- '\n'
- 'object.__str__(self)\n'
- '\n'
- ' Called by "str(object)", the default "__format__()" '
- 'implementation,\n'
- ' and the built-in function "print()", to compute the '
- '“informal” or\n'
- ' nicely printable string representation of an object. The '
- 'return\n'
- ' value must be a str object.\n'
- '\n'
- ' This method differs from "object.__repr__()" in that '
- 'there is no\n'
- ' expectation that "__str__()" return a valid Python '
- 'expression: a\n'
- ' more convenient or concise representation can be used.\n'
- '\n'
- ' The default implementation defined by the built-in type '
- '"object"\n'
- ' calls "object.__repr__()".\n'
- '\n'
- 'object.__bytes__(self)\n'
- '\n'
- ' Called by bytes to compute a byte-string representation '
- 'of an\n'
- ' object. This should return a "bytes" object. The "object" '
- 'class\n'
- ' itself does not provide this method.\n'
- '\n'
- 'object.__format__(self, format_spec)\n'
- '\n'
- ' Called by the "format()" built-in function, and by '
- 'extension,\n'
- ' evaluation of formatted string literals and the '
- '"str.format()"\n'
- ' method, to produce a “formatted” string representation of '
- 'an\n'
- ' object. The *format_spec* argument is a string that '
- 'contains a\n'
- ' description of the formatting options desired. The '
- 'interpretation\n'
- ' of the *format_spec* argument is up to the type '
- 'implementing\n'
- ' "__format__()", however most classes will either '
- 'delegate\n'
- ' formatting to one of the built-in types, or use a '
- 'similar\n'
- ' formatting option syntax.\n'
- '\n'
- ' See Format Specification Mini-Language for a description '
- 'of the\n'
- ' standard formatting syntax.\n'
- '\n'
- ' The return value must be a string object.\n'
- '\n'
- ' The default implementation by the "object" class should '
- 'be given an\n'
- ' empty *format_spec* string. It delegates to "__str__()".\n'
- '\n'
- ' Changed in version 3.4: The __format__ method of "object" '
- 'itself\n'
- ' raises a "TypeError" if passed any non-empty string.\n'
- '\n'
- ' Changed in version 3.7: "object.__format__(x, \'\')" is '
- 'now\n'
- ' equivalent to "str(x)" rather than "format(str(x), '
- '\'\')".\n'
- '\n'
- 'object.__lt__(self, other)\n'
- 'object.__le__(self, other)\n'
- 'object.__eq__(self, other)\n'
- 'object.__ne__(self, other)\n'
- 'object.__gt__(self, other)\n'
- 'object.__ge__(self, other)\n'
- '\n'
- ' These are the so-called “rich comparison” methods. The\n'
- ' correspondence between operator symbols and method names '
- 'is as\n'
- ' follows: "x<y" calls "x.__lt__(y)", "x<=y" calls '
- '"x.__le__(y)",\n'
- ' "x==y" calls "x.__eq__(y)", "x!=y" calls "x.__ne__(y)", '
- '"x>y" calls\n'
- ' "x.__gt__(y)", and "x>=y" calls "x.__ge__(y)".\n'
- '\n'
- ' A rich comparison method may return the singleton '
- '"NotImplemented"\n'
- ' if it does not implement the operation for a given pair '
- 'of\n'
- ' arguments. By convention, "False" and "True" are returned '
- 'for a\n'
- ' successful comparison. However, these methods can return '
- 'any value,\n'
- ' so if the comparison operator is used in a Boolean '
- 'context (e.g.,\n'
- ' in the condition of an "if" statement), Python will call '
- '"bool()"\n'
- ' on the value to determine if the result is true or '
- 'false.\n'
- '\n'
- ' By default, "object" implements "__eq__()" by using "is", '
- 'returning\n'
- ' "NotImplemented" in the case of a false comparison: "True '
- 'if x is y\n'
- ' else NotImplemented". For "__ne__()", by default it '
- 'delegates to\n'
- ' "__eq__()" and inverts the result unless it is '
- '"NotImplemented".\n'
- ' There are no other implied relationships among the '
- 'comparison\n'
- ' operators or default implementations; for example, the '
- 'truth of\n'
- ' "(x<y or x==y)" does not imply "x<=y". To automatically '
- 'generate\n'
- ' ordering operations from a single root operation, see\n'
- ' "functools.total_ordering()".\n'
- '\n'
- ' By default, the "object" class provides implementations '
- 'consistent\n'
- ' with Value comparisons: equality compares according to '
- 'object\n'
- ' identity, and order comparisons raise "TypeError". Each '
- 'default\n'
- ' method may generate these results directly, but may also '
- 'return\n'
- ' "NotImplemented".\n'
- '\n'
- ' See the paragraph on "__hash__()" for some important '
- 'notes on\n'
- ' creating *hashable* objects which support custom '
- 'comparison\n'
- ' operations and are usable as dictionary keys.\n'
- '\n'
- ' There are no swapped-argument versions of these methods '
- '(to be used\n'
- ' when the left argument does not support the operation but '
- 'the right\n'
- ' argument does); rather, "__lt__()" and "__gt__()" are '
- 'each other’s\n'
- ' reflection, "__le__()" and "__ge__()" are each other’s '
- 'reflection,\n'
- ' and "__eq__()" and "__ne__()" are their own reflection. '
- 'If the\n'
- ' operands are of different types, and the right operand’s '
- 'type is a\n'
- ' direct or indirect subclass of the left operand’s type, '
- 'the\n'
- ' reflected method of the right operand has priority, '
- 'otherwise the\n'
- ' left operand’s method has priority. Virtual subclassing '
- 'is not\n'
- ' considered.\n'
- '\n'
- ' When no appropriate method returns any value other than\n'
- ' "NotImplemented", the "==" and "!=" operators will fall '
- 'back to\n'
- ' "is" and "is not", respectively.\n'
- '\n'
- 'object.__hash__(self)\n'
- '\n'
- ' Called by built-in function "hash()" and for operations '
- 'on members\n'
- ' of hashed collections including "set", "frozenset", and '
- '"dict".\n'
- ' The "__hash__()" method should return an integer. The '
- 'only required\n'
- ' property is that objects which compare equal have the '
- 'same hash\n'
- ' value; it is advised to mix together the hash values of '
- 'the\n'
- ' components of the object that also play a part in '
- 'comparison of\n'
- ' objects by packing them into a tuple and hashing the '
- 'tuple.\n'
- ' Example:\n'
- '\n'
- ' def __hash__(self):\n'
- ' return hash((self.name, self.nick, self.color))\n'
- '\n'
- ' Note:\n'
- '\n'
- ' "hash()" truncates the value returned from an object’s '
- 'custom\n'
- ' "__hash__()" method to the size of a "Py_ssize_t". '
- 'This is\n'
- ' typically 8 bytes on 64-bit builds and 4 bytes on '
- '32-bit builds.\n'
- ' If an object’s "__hash__()" must interoperate on '
- 'builds of\n'
- ' different bit sizes, be sure to check the width on all '
- 'supported\n'
- ' builds. An easy way to do this is with "python -c '
- '"import sys;\n'
- ' print(sys.hash_info.width)"".\n'
- '\n'
- ' If a class does not define an "__eq__()" method it should '
- 'not\n'
- ' define a "__hash__()" operation either; if it defines '
- '"__eq__()"\n'
- ' but not "__hash__()", its instances will not be usable as '
- 'items in\n'
- ' hashable collections. If a class defines mutable objects '
- 'and\n'
- ' implements an "__eq__()" method, it should not implement\n'
- ' "__hash__()", since the implementation of *hashable* '
- 'collections\n'
- ' requires that a key’s hash value is immutable (if the '
- 'object’s hash\n'
- ' value changes, it will be in the wrong hash bucket).\n'
- '\n'
- ' User-defined classes have "__eq__()" and "__hash__()" '
- 'methods by\n'
- ' default (inherited from the "object" class); with them, '
- 'all objects\n'
- ' compare unequal (except with themselves) and '
- '"x.__hash__()" returns\n'
- ' an appropriate value such that "x == y" implies both that '
- '"x is y"\n'
- ' and "hash(x) == hash(y)".\n'
- '\n'
- ' A class that overrides "__eq__()" and does not define '
- '"__hash__()"\n'
- ' will have its "__hash__()" implicitly set to "None". '
- 'When the\n'
- ' "__hash__()" method of a class is "None", instances of '
- 'the class\n'
- ' will raise an appropriate "TypeError" when a program '
- 'attempts to\n'
- ' retrieve their hash value, and will also be correctly '
- 'identified as\n'
- ' unhashable when checking "isinstance(obj,\n'
- ' collections.abc.Hashable)".\n'
- '\n'
- ' If a class that overrides "__eq__()" needs to retain the\n'
- ' implementation of "__hash__()" from a parent class, the '
- 'interpreter\n'
- ' must be told this explicitly by setting "__hash__ =\n'
- ' <ParentClass>.__hash__".\n'
- '\n'
- ' If a class that does not override "__eq__()" wishes to '
- 'suppress\n'
- ' hash support, it should include "__hash__ = None" in the '
- 'class\n'
- ' definition. A class which defines its own "__hash__()" '
- 'that\n'
- ' explicitly raises a "TypeError" would be incorrectly '
- 'identified as\n'
- ' hashable by an "isinstance(obj, '
- 'collections.abc.Hashable)" call.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' By default, the "__hash__()" values of str and bytes '
- 'objects are\n'
- ' “salted” with an unpredictable random value. Although '
- 'they\n'
- ' remain constant within an individual Python process, '
- 'they are not\n'
- ' predictable between repeated invocations of Python.This '
- 'is\n'
- ' intended to provide protection against a '
- 'denial-of-service caused\n'
- ' by carefully chosen inputs that exploit the worst case\n'
- ' performance of a dict insertion, *O*(*n*^2) '
- 'complexity. See\n'
- ' http://ocert.org/advisories/ocert-2011-003.html for\n'
- ' details.Changing hash values affects the iteration '
- 'order of sets.\n'
- ' Python has never made guarantees about this ordering '
- '(and it\n'
- ' typically varies between 32-bit and 64-bit builds).See '
- 'also\n'
- ' "PYTHONHASHSEED".\n'
- '\n'
- ' Changed in version 3.3: Hash randomization is enabled by '
- 'default.\n'
- '\n'
- 'object.__bool__(self)\n'
- '\n'
- ' Called to implement truth value testing and the built-in '
- 'operation\n'
- ' "bool()"; should return "False" or "True". When this '
- 'method is not\n'
- ' defined, "__len__()" is called, if it is defined, and the '
- 'object is\n'
- ' considered true if its result is nonzero. If a class '
- 'defines\n'
- ' neither "__len__()" nor "__bool__()" (which is true of '
- 'the "object"\n'
- ' class itself), all its instances are considered true.\n'
- '\n'
- '\n'
- 'Customizing attribute access\n'
- '============================\n'
- '\n'
- 'The following methods can be defined to customize the '
- 'meaning of\n'
- 'attribute access (use of, assignment to, or deletion of '
- '"x.name") for\n'
- 'class instances.\n'
- '\n'
- 'object.__getattr__(self, name)\n'
- '\n'
- ' Called when the default attribute access fails with an\n'
- ' "AttributeError" (either "__getattribute__()" raises an\n'
- ' "AttributeError" because *name* is not an instance '
- 'attribute or an\n'
- ' attribute in the class tree for "self"; or "__get__()" of '
- 'a *name*\n'
- ' property raises "AttributeError"). This method should '
- 'either\n'
- ' return the (computed) attribute value or raise an '
- '"AttributeError"\n'
- ' exception. The "object" class itself does not provide '
- 'this method.\n'
- '\n'
- ' Note that if the attribute is found through the normal '
- 'mechanism,\n'
- ' "__getattr__()" is not called. (This is an intentional '
- 'asymmetry\n'
- ' between "__getattr__()" and "__setattr__()".) This is '
- 'done both for\n'
- ' efficiency reasons and because otherwise "__getattr__()" '
- 'would have\n'
- ' no way to access other attributes of the instance. Note '
- 'that at\n'
- ' least for instance variables, you can fake total control '
- 'by not\n'
- ' inserting any values in the instance attribute dictionary '
- '(but\n'
- ' instead inserting them in another object). See the\n'
- ' "__getattribute__()" method below for a way to actually '
- 'get total\n'
- ' control over attribute access.\n'
- '\n'
- 'object.__getattribute__(self, name)\n'
- '\n'
- ' Called unconditionally to implement attribute accesses '
- 'for\n'
- ' instances of the class. If the class also defines '
- '"__getattr__()",\n'
- ' the latter will not be called unless "__getattribute__()" '
- 'either\n'
- ' calls it explicitly or raises an "AttributeError". This '
- 'method\n'
- ' should return the (computed) attribute value or raise an\n'
- ' "AttributeError" exception. In order to avoid infinite '
- 'recursion in\n'
- ' this method, its implementation should always call the '
- 'base class\n'
- ' method with the same name to access any attributes it '
- 'needs, for\n'
- ' example, "object.__getattribute__(self, name)".\n'
- '\n'
- ' Note:\n'
- '\n'
- ' This method may still be bypassed when looking up '
- 'special methods\n'
- ' as the result of implicit invocation via language '
- 'syntax or\n'
- ' built-in functions. See Special method lookup.\n'
- '\n'
- ' For certain sensitive attribute accesses, raises an '
- 'auditing event\n'
- ' "object.__getattr__" with arguments "obj" and "name".\n'
- '\n'
- 'object.__setattr__(self, name, value)\n'
- '\n'
- ' Called when an attribute assignment is attempted. This '
- 'is called\n'
- ' instead of the normal mechanism (i.e. store the value in '
- 'the\n'
- ' instance dictionary). *name* is the attribute name, '
- '*value* is the\n'
- ' value to be assigned to it.\n'
- '\n'
- ' If "__setattr__()" wants to assign to an instance '
- 'attribute, it\n'
- ' should call the base class method with the same name, for '
- 'example,\n'
- ' "object.__setattr__(self, name, value)".\n'
- '\n'
- ' For certain sensitive attribute assignments, raises an '
- 'auditing\n'
- ' event "object.__setattr__" with arguments "obj", "name", '
- '"value".\n'
- '\n'
- 'object.__delattr__(self, name)\n'
- '\n'
- ' Like "__setattr__()" but for attribute deletion instead '
- 'of\n'
- ' assignment. This should only be implemented if "del '
- 'obj.name" is\n'
- ' meaningful for the object.\n'
- '\n'
- ' For certain sensitive attribute deletions, raises an '
- 'auditing event\n'
- ' "object.__delattr__" with arguments "obj" and "name".\n'
- '\n'
- 'object.__dir__(self)\n'
- '\n'
- ' Called when "dir()" is called on the object. An iterable '
- 'must be\n'
- ' returned. "dir()" converts the returned iterable to a '
- 'list and\n'
- ' sorts it.\n'
- '\n'
- '\n'
- 'Customizing module attribute access\n'
- '-----------------------------------\n'
- '\n'
- 'Special names "__getattr__" and "__dir__" can be also used '
- 'to\n'
- 'customize access to module attributes. The "__getattr__" '
- 'function at\n'
- 'the module level should accept one argument which is the '
- 'name of an\n'
- 'attribute and return the computed value or raise an '
- '"AttributeError".\n'
- 'If an attribute is not found on a module object through the '
- 'normal\n'
- 'lookup, i.e. "object.__getattribute__()", then "__getattr__" '
- 'is\n'
- 'searched in the module "__dict__" before raising an '
- '"AttributeError".\n'
- 'If found, it is called with the attribute name and the '
- 'result is\n'
- 'returned.\n'
- '\n'
- 'The "__dir__" function should accept no arguments, and '
- 'return an\n'
- 'iterable of strings that represents the names accessible on '
- 'module. If\n'
- 'present, this function overrides the standard "dir()" search '
- 'on a\n'
- 'module.\n'
- '\n'
- 'For a more fine grained customization of the module behavior '
- '(setting\n'
- 'attributes, properties, etc.), one can set the "__class__" '
- 'attribute\n'
- 'of a module object to a subclass of "types.ModuleType". For '
- 'example:\n'
- '\n'
- ' import sys\n'
- ' from types import ModuleType\n'
- '\n'
- ' class VerboseModule(ModuleType):\n'
- ' def __repr__(self):\n'
- " return f'Verbose {self.__name__}'\n"
- '\n'
- ' def __setattr__(self, attr, value):\n'
- " print(f'Setting {attr}...')\n"
- ' super().__setattr__(attr, value)\n'
- '\n'
- ' sys.modules[__name__].__class__ = VerboseModule\n'
- '\n'
- 'Note:\n'
- '\n'
- ' Defining module "__getattr__" and setting module '
- '"__class__" only\n'
- ' affect lookups made using the attribute access syntax – '
- 'directly\n'
- ' accessing the module globals (whether by code within the '
- 'module, or\n'
- ' via a reference to the module’s globals dictionary) is '
- 'unaffected.\n'
- '\n'
- 'Changed in version 3.5: "__class__" module attribute is now '
- 'writable.\n'
- '\n'
- 'Added in version 3.7: "__getattr__" and "__dir__" module '
- 'attributes.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 562** - Module __getattr__ and __dir__\n'
- ' Describes the "__getattr__" and "__dir__" functions on '
- 'modules.\n'
- '\n'
- '\n'
- 'Implementing Descriptors\n'
- '------------------------\n'
- '\n'
- 'The following methods only apply when an instance of the '
- 'class\n'
- 'containing the method (a so-called *descriptor* class) '
- 'appears in an\n'
- '*owner* class (the descriptor must be in either the owner’s '
- 'class\n'
- 'dictionary or in the class dictionary for one of its '
- 'parents). In the\n'
- 'examples below, “the attribute” refers to the attribute '
- 'whose name is\n'
- 'the key of the property in the owner class’ "__dict__". The '
- '"object"\n'
- 'class itself does not implement any of these protocols.\n'
- '\n'
- 'object.__get__(self, instance, owner=None)\n'
- '\n'
- ' Called to get the attribute of the owner class (class '
- 'attribute\n'
- ' access) or of an instance of that class (instance '
- 'attribute\n'
- ' access). The optional *owner* argument is the owner '
- 'class, while\n'
- ' *instance* is the instance that the attribute was '
- 'accessed through,\n'
- ' or "None" when the attribute is accessed through the '
- '*owner*.\n'
- '\n'
- ' This method should return the computed attribute value or '
- 'raise an\n'
- ' "AttributeError" exception.\n'
- '\n'
- ' **PEP 252** specifies that "__get__()" is callable with '
- 'one or two\n'
- ' arguments. Python’s own built-in descriptors support '
- 'this\n'
- ' specification; however, it is likely that some '
- 'third-party tools\n'
- ' have descriptors that require both arguments. Python’s '
- 'own\n'
- ' "__getattribute__()" implementation always passes in both '
- 'arguments\n'
- ' whether they are required or not.\n'
- '\n'
- 'object.__set__(self, instance, value)\n'
- '\n'
- ' Called to set the attribute on an instance *instance* of '
- 'the owner\n'
- ' class to a new value, *value*.\n'
- '\n'
- ' Note, adding "__set__()" or "__delete__()" changes the '
- 'kind of\n'
- ' descriptor to a “data descriptor”. See Invoking '
- 'Descriptors for\n'
- ' more details.\n'
- '\n'
- 'object.__delete__(self, instance)\n'
- '\n'
- ' Called to delete the attribute on an instance *instance* '
- 'of the\n'
- ' owner class.\n'
- '\n'
- 'Instances of descriptors may also have the "__objclass__" '
- 'attribute\n'
- 'present:\n'
- '\n'
- 'object.__objclass__\n'
- '\n'
- ' The attribute "__objclass__" is interpreted by the '
- '"inspect" module\n'
- ' as specifying the class where this object was defined '
- '(setting this\n'
- ' appropriately can assist in runtime introspection of '
- 'dynamic class\n'
- ' attributes). For callables, it may indicate that an '
- 'instance of the\n'
- ' given type (or a subclass) is expected or required as the '
- 'first\n'
- ' positional argument (for example, CPython sets this '
- 'attribute for\n'
- ' unbound methods that are implemented in C).\n'
- '\n'
- '\n'
- 'Invoking Descriptors\n'
- '--------------------\n'
- '\n'
- 'In general, a descriptor is an object attribute with '
- '“binding\n'
- 'behavior”, one whose attribute access has been overridden by '
- 'methods\n'
- 'in the descriptor protocol: "__get__()", "__set__()", and\n'
- '"__delete__()". If any of those methods are defined for an '
- 'object, it\n'
- 'is said to be a descriptor.\n'
- '\n'
- 'The default behavior for attribute access is to get, set, or '
- 'delete\n'
- 'the attribute from an object’s dictionary. For instance, '
- '"a.x" has a\n'
- 'lookup chain starting with "a.__dict__[\'x\']", then\n'
- '"type(a).__dict__[\'x\']", and continuing through the base '
- 'classes of\n'
- '"type(a)" excluding metaclasses.\n'
- '\n'
- 'However, if the looked-up value is an object defining one of '
- 'the\n'
- 'descriptor methods, then Python may override the default '
- 'behavior and\n'
- 'invoke the descriptor method instead. Where this occurs in '
- 'the\n'
- 'precedence chain depends on which descriptor methods were '
- 'defined and\n'
- 'how they were called.\n'
- '\n'
- 'The starting point for descriptor invocation is a binding, '
- '"a.x". How\n'
- 'the arguments are assembled depends on "a":\n'
- '\n'
- 'Direct Call\n'
- ' The simplest and least common call is when user code '
- 'directly\n'
- ' invokes a descriptor method: "x.__get__(a)".\n'
- '\n'
- 'Instance Binding\n'
- ' If binding to an object instance, "a.x" is transformed '
- 'into the\n'
- ' call: "type(a).__dict__[\'x\'].__get__(a, type(a))".\n'
- '\n'
- 'Class Binding\n'
- ' If binding to a class, "A.x" is transformed into the '
- 'call:\n'
- ' "A.__dict__[\'x\'].__get__(None, A)".\n'
- '\n'
- 'Super Binding\n'
- ' A dotted lookup such as "super(A, a).x" searches\n'
- ' "a.__class__.__mro__" for a base class "B" following "A" '
- 'and then\n'
- ' returns "B.__dict__[\'x\'].__get__(a, A)". If not a '
- 'descriptor, "x"\n'
- ' is returned unchanged.\n'
- '\n'
- 'For instance bindings, the precedence of descriptor '
- 'invocation depends\n'
- 'on which descriptor methods are defined. A descriptor can '
- 'define any\n'
- 'combination of "__get__()", "__set__()" and "__delete__()". '
- 'If it\n'
- 'does not define "__get__()", then accessing the attribute '
- 'will return\n'
- 'the descriptor object itself unless there is a value in the '
- 'object’s\n'
- 'instance dictionary. If the descriptor defines "__set__()" '
- 'and/or\n'
- '"__delete__()", it is a data descriptor; if it defines '
- 'neither, it is\n'
- 'a non-data descriptor. Normally, data descriptors define '
- 'both\n'
- '"__get__()" and "__set__()", while non-data descriptors have '
- 'just the\n'
- '"__get__()" method. Data descriptors with "__get__()" and '
- '"__set__()"\n'
- '(and/or "__delete__()") defined always override a '
- 'redefinition in an\n'
- 'instance dictionary. In contrast, non-data descriptors can '
- 'be\n'
- 'overridden by instances.\n'
- '\n'
- 'Python methods (including those decorated with '
- '"@staticmethod" and\n'
- '"@classmethod") are implemented as non-data descriptors. '
- 'Accordingly,\n'
- 'instances can redefine and override methods. This allows '
- 'individual\n'
- 'instances to acquire behaviors that differ from other '
- 'instances of the\n'
- 'same class.\n'
- '\n'
- 'The "property()" function is implemented as a data '
- 'descriptor.\n'
- 'Accordingly, instances cannot override the behavior of a '
- 'property.\n'
- '\n'
- '\n'
- '__slots__\n'
- '---------\n'
- '\n'
- '*__slots__* allow us to explicitly declare data members '
- '(like\n'
- 'properties) and deny the creation of "__dict__" and '
- '*__weakref__*\n'
- '(unless explicitly declared in *__slots__* or available in a '
- 'parent.)\n'
- '\n'
- 'The space saved over using "__dict__" can be significant. '
- 'Attribute\n'
- 'lookup speed can be significantly improved as well.\n'
- '\n'
- 'object.__slots__\n'
- '\n'
- ' This class variable can be assigned a string, iterable, '
- 'or sequence\n'
- ' of strings with variable names used by instances. '
- '*__slots__*\n'
- ' reserves space for the declared variables and prevents '
- 'the\n'
- ' automatic creation of "__dict__" and *__weakref__* for '
- 'each\n'
- ' instance.\n'
- '\n'
- 'Notes on using *__slots__*:\n'
- '\n'
- '* When inheriting from a class without *__slots__*, the '
- '"__dict__" and\n'
- ' *__weakref__* attribute of the instances will always be '
- 'accessible.\n'
- '\n'
- '* Without a "__dict__" variable, instances cannot be '
- 'assigned new\n'
- ' variables not listed in the *__slots__* definition. '
- 'Attempts to\n'
- ' assign to an unlisted variable name raises '
- '"AttributeError". If\n'
- ' dynamic assignment of new variables is desired, then add\n'
- ' "\'__dict__\'" to the sequence of strings in the '
- '*__slots__*\n'
- ' declaration.\n'
- '\n'
- '* Without a *__weakref__* variable for each instance, '
- 'classes defining\n'
- ' *__slots__* do not support "weak references" to its '
- 'instances. If\n'
- ' weak reference support is needed, then add '
- '"\'__weakref__\'" to the\n'
- ' sequence of strings in the *__slots__* declaration.\n'
- '\n'
- '* *__slots__* are implemented at the class level by '
- 'creating\n'
- ' descriptors for each variable name. As a result, class '
- 'attributes\n'
- ' cannot be used to set default values for instance '
- 'variables defined\n'
- ' by *__slots__*; otherwise, the class attribute would '
- 'overwrite the\n'
- ' descriptor assignment.\n'
- '\n'
- '* The action of a *__slots__* declaration is not limited to '
- 'the class\n'
- ' where it is defined. *__slots__* declared in parents are '
- 'available\n'
- ' in child classes. However, instances of a child subclass '
- 'will get a\n'
- ' "__dict__" and *__weakref__* unless the subclass also '
- 'defines\n'
- ' *__slots__* (which should only contain names of any '
- '*additional*\n'
- ' slots).\n'
- '\n'
- '* If a class defines a slot also defined in a base class, '
- 'the instance\n'
- ' variable defined by the base class slot is inaccessible '
- '(except by\n'
- ' retrieving its descriptor directly from the base class). '
- 'This\n'
- ' renders the meaning of the program undefined. In the '
- 'future, a\n'
- ' check may be added to prevent this.\n'
- '\n'
- '* "TypeError" will be raised if nonempty *__slots__* are '
- 'defined for a\n'
- ' class derived from a ""variable-length" built-in type" '
- 'such as\n'
- ' "int", "bytes", and "tuple".\n'
- '\n'
- '* Any non-string *iterable* may be assigned to *__slots__*.\n'
- '\n'
- '* If a "dictionary" is used to assign *__slots__*, the '
- 'dictionary keys\n'
- ' will be used as the slot names. The values of the '
- 'dictionary can be\n'
- ' used to provide per-attribute docstrings that will be '
- 'recognised by\n'
- ' "inspect.getdoc()" and displayed in the output of '
- '"help()".\n'
- '\n'
- '* "__class__" assignment works only if both classes have the '
- 'same\n'
- ' *__slots__*.\n'
- '\n'
- '* Multiple inheritance with multiple slotted parent classes '
- 'can be\n'
- ' used, but only one parent is allowed to have attributes '
- 'created by\n'
- ' slots (the other bases must have empty slot layouts) - '
- 'violations\n'
- ' raise "TypeError".\n'
- '\n'
- '* If an *iterator* is used for *__slots__* then a '
- '*descriptor* is\n'
- ' created for each of the iterator’s values. However, the '
- '*__slots__*\n'
- ' attribute will be an empty iterator.\n'
- '\n'
- '\n'
- 'Customizing class creation\n'
- '==========================\n'
- '\n'
- 'Whenever a class inherits from another class, '
- '"__init_subclass__()" is\n'
- 'called on the parent class. This way, it is possible to '
- 'write classes\n'
- 'which change the behavior of subclasses. This is closely '
- 'related to\n'
- 'class decorators, but where class decorators only affect the '
- 'specific\n'
- 'class they’re applied to, "__init_subclass__" solely applies '
- 'to future\n'
- 'subclasses of the class defining the method.\n'
- '\n'
- 'classmethod object.__init_subclass__(cls)\n'
- '\n'
- ' This method is called whenever the containing class is '
- 'subclassed.\n'
- ' *cls* is then the new subclass. If defined as a normal '
- 'instance\n'
- ' method, this method is implicitly converted to a class '
- 'method.\n'
- '\n'
- ' Keyword arguments which are given to a new class are '
- 'passed to the\n'
- ' parent class’s "__init_subclass__". For compatibility '
- 'with other\n'
- ' classes using "__init_subclass__", one should take out '
- 'the needed\n'
- ' keyword arguments and pass the others over to the base '
- 'class, as\n'
- ' in:\n'
- '\n'
- ' class Philosopher:\n'
- ' def __init_subclass__(cls, /, default_name, '
- '**kwargs):\n'
- ' super().__init_subclass__(**kwargs)\n'
- ' cls.default_name = default_name\n'
- '\n'
- ' class AustralianPhilosopher(Philosopher, '
- 'default_name="Bruce"):\n'
- ' pass\n'
- '\n'
- ' The default implementation "object.__init_subclass__" '
- 'does nothing,\n'
- ' but raises an error if it is called with any arguments.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' The metaclass hint "metaclass" is consumed by the rest '
- 'of the\n'
- ' type machinery, and is never passed to '
- '"__init_subclass__"\n'
- ' implementations. The actual metaclass (rather than the '
- 'explicit\n'
- ' hint) can be accessed as "type(cls)".\n'
- '\n'
- ' Added in version 3.6.\n'
- '\n'
- 'When a class is created, "type.__new__()" scans the class '
- 'variables\n'
- 'and makes callbacks to those with a "__set_name__()" hook.\n'
- '\n'
- 'object.__set_name__(self, owner, name)\n'
- '\n'
- ' Automatically called at the time the owning class *owner* '
- 'is\n'
- ' created. The object has been assigned to *name* in that '
- 'class:\n'
- '\n'
- ' class A:\n'
- ' x = C() # Automatically calls: x.__set_name__(A, '
- "'x')\n"
- '\n'
- ' If the class variable is assigned after the class is '
- 'created,\n'
- ' "__set_name__()" will not be called automatically. If '
- 'needed,\n'
- ' "__set_name__()" can be called directly:\n'
- '\n'
- ' class A:\n'
- ' pass\n'
- '\n'
- ' c = C()\n'
- ' A.x = c # The hook is not called\n'
- " c.__set_name__(A, 'x') # Manually invoke the hook\n"
- '\n'
- ' See Creating the class object for more details.\n'
- '\n'
- ' Added in version 3.6.\n'
- '\n'
- '\n'
- 'Metaclasses\n'
- '-----------\n'
- '\n'
- 'By default, classes are constructed using "type()". The '
- 'class body is\n'
- 'executed in a new namespace and the class name is bound '
- 'locally to the\n'
- 'result of "type(name, bases, namespace)".\n'
- '\n'
- 'The class creation process can be customized by passing the\n'
- '"metaclass" keyword argument in the class definition line, '
- 'or by\n'
- 'inheriting from an existing class that included such an '
- 'argument. In\n'
- 'the following example, both "MyClass" and "MySubclass" are '
- 'instances\n'
- 'of "Meta":\n'
- '\n'
- ' class Meta(type):\n'
- ' pass\n'
- '\n'
- ' class MyClass(metaclass=Meta):\n'
- ' pass\n'
- '\n'
- ' class MySubclass(MyClass):\n'
- ' pass\n'
- '\n'
- 'Any other keyword arguments that are specified in the class '
- 'definition\n'
- 'are passed through to all metaclass operations described '
- 'below.\n'
- '\n'
- 'When a class definition is executed, the following steps '
- 'occur:\n'
- '\n'
- '* MRO entries are resolved;\n'
- '\n'
- '* the appropriate metaclass is determined;\n'
- '\n'
- '* the class namespace is prepared;\n'
- '\n'
- '* the class body is executed;\n'
- '\n'
- '* the class object is created.\n'
- '\n'
- '\n'
- 'Resolving MRO entries\n'
- '---------------------\n'
- '\n'
- 'object.__mro_entries__(self, bases)\n'
- '\n'
- ' If a base that appears in a class definition is not an '
- 'instance of\n'
- ' "type", then an "__mro_entries__()" method is searched on '
- 'the base.\n'
- ' If an "__mro_entries__()" method is found, the base is '
- 'substituted\n'
- ' with the result of a call to "__mro_entries__()" when '
- 'creating the\n'
- ' class. The method is called with the original bases tuple '
- 'passed to\n'
- ' the *bases* parameter, and must return a tuple of classes '
- 'that will\n'
- ' be used instead of the base. The returned tuple may be '
- 'empty: in\n'
- ' these cases, the original base is ignored.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' "types.resolve_bases()"\n'
- ' Dynamically resolve bases that are not instances of '
- '"type".\n'
- '\n'
- ' "types.get_original_bases()"\n'
- ' Retrieve a class’s “original bases” prior to '
- 'modifications by\n'
- ' "__mro_entries__()".\n'
- '\n'
- ' **PEP 560**\n'
- ' Core support for typing module and generic types.\n'
- '\n'
- '\n'
- 'Determining the appropriate metaclass\n'
- '-------------------------------------\n'
- '\n'
- 'The appropriate metaclass for a class definition is '
- 'determined as\n'
- 'follows:\n'
- '\n'
- '* if no bases and no explicit metaclass are given, then '
- '"type()" is\n'
- ' used;\n'
- '\n'
- '* if an explicit metaclass is given and it is *not* an '
- 'instance of\n'
- ' "type()", then it is used directly as the metaclass;\n'
- '\n'
- '* if an instance of "type()" is given as the explicit '
- 'metaclass, or\n'
- ' bases are defined, then the most derived metaclass is '
- 'used.\n'
- '\n'
- 'The most derived metaclass is selected from the explicitly '
- 'specified\n'
- 'metaclass (if any) and the metaclasses (i.e. "type(cls)") of '
- 'all\n'
- 'specified base classes. The most derived metaclass is one '
- 'which is a\n'
- 'subtype of *all* of these candidate metaclasses. If none of '
- 'the\n'
- 'candidate metaclasses meets that criterion, then the class '
- 'definition\n'
- 'will fail with "TypeError".\n'
- '\n'
- '\n'
- 'Preparing the class namespace\n'
- '-----------------------------\n'
- '\n'
- 'Once the appropriate metaclass has been identified, then the '
- 'class\n'
- 'namespace is prepared. If the metaclass has a "__prepare__" '
- 'attribute,\n'
- 'it is called as "namespace = metaclass.__prepare__(name, '
- 'bases,\n'
- '**kwds)" (where the additional keyword arguments, if any, '
- 'come from\n'
- 'the class definition). The "__prepare__" method should be '
- 'implemented\n'
- 'as a "classmethod". The namespace returned by "__prepare__" '
- 'is passed\n'
- 'in to "__new__", but when the final class object is created '
- 'the\n'
- 'namespace is copied into a new "dict".\n'
- '\n'
- 'If the metaclass has no "__prepare__" attribute, then the '
- 'class\n'
- 'namespace is initialised as an empty ordered mapping.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 3115** - Metaclasses in Python 3000\n'
- ' Introduced the "__prepare__" namespace hook\n'
- '\n'
- '\n'
- 'Executing the class body\n'
- '------------------------\n'
- '\n'
- 'The class body is executed (approximately) as "exec(body, '
- 'globals(),\n'
- 'namespace)". The key difference from a normal call to '
- '"exec()" is that\n'
- 'lexical scoping allows the class body (including any '
- 'methods) to\n'
- 'reference names from the current and outer scopes when the '
- 'class\n'
- 'definition occurs inside a function.\n'
- '\n'
- 'However, even when the class definition occurs inside the '
- 'function,\n'
- 'methods defined inside the class still cannot see names '
- 'defined at the\n'
- 'class scope. Class variables must be accessed through the '
- 'first\n'
- 'parameter of instance or class methods, or through the '
- 'implicit\n'
- 'lexically scoped "__class__" reference described in the next '
- 'section.\n'
- '\n'
- '\n'
- 'Creating the class object\n'
- '-------------------------\n'
- '\n'
- 'Once the class namespace has been populated by executing the '
- 'class\n'
- 'body, the class object is created by calling '
- '"metaclass(name, bases,\n'
- 'namespace, **kwds)" (the additional keywords passed here are '
- 'the same\n'
- 'as those passed to "__prepare__").\n'
- '\n'
- 'This class object is the one that will be referenced by the '
- 'zero-\n'
- 'argument form of "super()". "__class__" is an implicit '
- 'closure\n'
- 'reference created by the compiler if any methods in a class '
- 'body refer\n'
- 'to either "__class__" or "super". This allows the zero '
- 'argument form\n'
- 'of "super()" to correctly identify the class being defined '
- 'based on\n'
- 'lexical scoping, while the class or instance that was used '
- 'to make the\n'
- 'current call is identified based on the first argument '
- 'passed to the\n'
- 'method.\n'
- '\n'
- '**CPython implementation detail:** In CPython 3.6 and later, '
- 'the\n'
- '"__class__" cell is passed to the metaclass as a '
- '"__classcell__" entry\n'
- 'in the class namespace. If present, this must be propagated '
- 'up to the\n'
- '"type.__new__" call in order for the class to be '
- 'initialised\n'
- 'correctly. Failing to do so will result in a "RuntimeError" '
- 'in Python\n'
- '3.8.\n'
- '\n'
- 'When using the default metaclass "type", or any metaclass '
- 'that\n'
- 'ultimately calls "type.__new__", the following additional\n'
- 'customization steps are invoked after creating the class '
- 'object:\n'
- '\n'
- '1. The "type.__new__" method collects all of the attributes '
- 'in the\n'
- ' class namespace that define a "__set_name__()" method;\n'
- '\n'
- '2. Those "__set_name__" methods are called with the class '
- 'being\n'
- ' defined and the assigned name of that particular '
- 'attribute;\n'
- '\n'
- '3. The "__init_subclass__()" hook is called on the immediate '
- 'parent of\n'
- ' the new class in its method resolution order.\n'
- '\n'
- 'After the class object is created, it is passed to the '
- 'class\n'
- 'decorators included in the class definition (if any) and the '
- 'resulting\n'
- 'object is bound in the local namespace as the defined '
- 'class.\n'
- '\n'
- 'When a new class is created by "type.__new__", the object '
- 'provided as\n'
- 'the namespace parameter is copied to a new ordered mapping '
- 'and the\n'
- 'original object is discarded. The new copy is wrapped in a '
- 'read-only\n'
- 'proxy, which becomes the "__dict__" attribute of the class '
- 'object.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 3135** - New super\n'
- ' Describes the implicit "__class__" closure reference\n'
- '\n'
- '\n'
- 'Uses for metaclasses\n'
- '--------------------\n'
- '\n'
- 'The potential uses for metaclasses are boundless. Some ideas '
- 'that have\n'
- 'been explored include enum, logging, interface checking, '
- 'automatic\n'
- 'delegation, automatic property creation, proxies, '
- 'frameworks, and\n'
- 'automatic resource locking/synchronization.\n'
- '\n'
- '\n'
- 'Customizing instance and subclass checks\n'
- '========================================\n'
- '\n'
- 'The following methods are used to override the default '
- 'behavior of the\n'
- '"isinstance()" and "issubclass()" built-in functions.\n'
- '\n'
- 'In particular, the metaclass "abc.ABCMeta" implements these '
- 'methods in\n'
- 'order to allow the addition of Abstract Base Classes (ABCs) '
- 'as\n'
- '“virtual base classes” to any class or type (including '
- 'built-in\n'
- 'types), including other ABCs.\n'
- '\n'
- 'type.__instancecheck__(self, instance)\n'
- '\n'
- ' Return true if *instance* should be considered a (direct '
- 'or\n'
- ' indirect) instance of *class*. If defined, called to '
- 'implement\n'
- ' "isinstance(instance, class)".\n'
- '\n'
- 'type.__subclasscheck__(self, subclass)\n'
- '\n'
- ' Return true if *subclass* should be considered a (direct '
- 'or\n'
- ' indirect) subclass of *class*. If defined, called to '
- 'implement\n'
- ' "issubclass(subclass, class)".\n'
- '\n'
- 'Note that these methods are looked up on the type '
- '(metaclass) of a\n'
- 'class. They cannot be defined as class methods in the '
- 'actual class.\n'
- 'This is consistent with the lookup of special methods that '
- 'are called\n'
- 'on instances, only in this case the instance is itself a '
- 'class.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 3119** - Introducing Abstract Base Classes\n'
- ' Includes the specification for customizing '
- '"isinstance()" and\n'
- ' "issubclass()" behavior through "__instancecheck__()" '
- 'and\n'
- ' "__subclasscheck__()", with motivation for this '
- 'functionality in\n'
- ' the context of adding Abstract Base Classes (see the '
- '"abc"\n'
- ' module) to the language.\n'
- '\n'
- '\n'
- 'Emulating generic types\n'
- '=======================\n'
- '\n'
- 'When using *type annotations*, it is often useful to '
- '*parameterize* a\n'
- '*generic type* using Python’s square-brackets notation. For '
- 'example,\n'
- 'the annotation "list[int]" might be used to signify a "list" '
- 'in which\n'
- 'all the elements are of type "int".\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 484** - Type Hints\n'
- ' Introducing Python’s framework for type annotations\n'
- '\n'
- ' Generic Alias Types\n'
- ' Documentation for objects representing parameterized '
- 'generic\n'
- ' classes\n'
- '\n'
- ' Generics, user-defined generics and "typing.Generic"\n'
- ' Documentation on how to implement generic classes that '
- 'can be\n'
- ' parameterized at runtime and understood by static '
- 'type-checkers.\n'
- '\n'
- 'A class can *generally* only be parameterized if it defines '
- 'the\n'
- 'special class method "__class_getitem__()".\n'
- '\n'
- 'classmethod object.__class_getitem__(cls, key)\n'
- '\n'
- ' Return an object representing the specialization of a '
- 'generic class\n'
- ' by type arguments found in *key*.\n'
- '\n'
- ' When defined on a class, "__class_getitem__()" is '
- 'automatically a\n'
- ' class method. As such, there is no need for it to be '
- 'decorated with\n'
- ' "@classmethod" when it is defined.\n'
- '\n'
- '\n'
- 'The purpose of *__class_getitem__*\n'
- '----------------------------------\n'
- '\n'
- 'The purpose of "__class_getitem__()" is to allow runtime\n'
- 'parameterization of standard-library generic classes in '
- 'order to more\n'
- 'easily apply *type hints* to these classes.\n'
- '\n'
- 'To implement custom generic classes that can be '
- 'parameterized at\n'
- 'runtime and understood by static type-checkers, users should '
- 'either\n'
- 'inherit from a standard library class that already '
- 'implements\n'
- '"__class_getitem__()", or inherit from "typing.Generic", '
- 'which has its\n'
- 'own implementation of "__class_getitem__()".\n'
- '\n'
- 'Custom implementations of "__class_getitem__()" on classes '
- 'defined\n'
- 'outside of the standard library may not be understood by '
- 'third-party\n'
- 'type-checkers such as mypy. Using "__class_getitem__()" on '
- 'any class\n'
- 'for purposes other than type hinting is discouraged.\n'
- '\n'
- '\n'
- '*__class_getitem__* versus *__getitem__*\n'
- '----------------------------------------\n'
- '\n'
- 'Usually, the subscription of an object using square brackets '
- 'will call\n'
- 'the "__getitem__()" instance method defined on the object’s '
- 'class.\n'
- 'However, if the object being subscribed is itself a class, '
- 'the class\n'
- 'method "__class_getitem__()" may be called instead.\n'
- '"__class_getitem__()" should return a GenericAlias object if '
- 'it is\n'
- 'properly defined.\n'
- '\n'
- 'Presented with the *expression* "obj[x]", the Python '
- 'interpreter\n'
- 'follows something like the following process to decide '
- 'whether\n'
- '"__getitem__()" or "__class_getitem__()" should be called:\n'
- '\n'
- ' from inspect import isclass\n'
- '\n'
- ' def subscribe(obj, x):\n'
- ' """Return the result of the expression \'obj[x]\'"""\n'
- '\n'
- ' class_of_obj = type(obj)\n'
- '\n'
- ' # If the class of obj defines __getitem__,\n'
- ' # call class_of_obj.__getitem__(obj, x)\n'
- " if hasattr(class_of_obj, '__getitem__'):\n"
- ' return class_of_obj.__getitem__(obj, x)\n'
- '\n'
- ' # Else, if obj is a class and defines '
- '__class_getitem__,\n'
- ' # call obj.__class_getitem__(x)\n'
- ' elif isclass(obj) and hasattr(obj, '
- "'__class_getitem__'):\n"
- ' return obj.__class_getitem__(x)\n'
- '\n'
- ' # Else, raise an exception\n'
- ' else:\n'
- ' raise TypeError(\n'
- ' f"\'{class_of_obj.__name__}\' object is not '
- 'subscriptable"\n'
- ' )\n'
- '\n'
- 'In Python, all classes are themselves instances of other '
- 'classes. The\n'
- 'class of a class is known as that class’s *metaclass*, and '
- 'most\n'
- 'classes have the "type" class as their metaclass. "type" '
- 'does not\n'
- 'define "__getitem__()", meaning that expressions such as '
- '"list[int]",\n'
- '"dict[str, float]" and "tuple[str, bytes]" all result in\n'
- '"__class_getitem__()" being called:\n'
- '\n'
- ' >>> # list has class "type" as its metaclass, like most '
- 'classes:\n'
- ' >>> type(list)\n'
- " <class 'type'>\n"
- ' >>> type(dict) == type(list) == type(tuple) == type(str) '
- '== type(bytes)\n'
- ' True\n'
- ' >>> # "list[int]" calls "list.__class_getitem__(int)"\n'
- ' >>> list[int]\n'
- ' list[int]\n'
- ' >>> # list.__class_getitem__ returns a GenericAlias '
- 'object:\n'
- ' >>> type(list[int])\n'
- " <class 'types.GenericAlias'>\n"
- '\n'
- 'However, if a class has a custom metaclass that defines\n'
- '"__getitem__()", subscribing the class may result in '
- 'different\n'
- 'behaviour. An example of this can be found in the "enum" '
- 'module:\n'
- '\n'
- ' >>> from enum import Enum\n'
- ' >>> class Menu(Enum):\n'
- ' ... """A breakfast menu"""\n'
- " ... SPAM = 'spam'\n"
- " ... BACON = 'bacon'\n"
- ' ...\n'
- ' >>> # Enum classes have a custom metaclass:\n'
- ' >>> type(Menu)\n'
- " <class 'enum.EnumMeta'>\n"
- ' >>> # EnumMeta defines __getitem__,\n'
- ' >>> # so __class_getitem__ is not called,\n'
- ' >>> # and the result is not a GenericAlias object:\n'
- " >>> Menu['SPAM']\n"
- " <Menu.SPAM: 'spam'>\n"
- " >>> type(Menu['SPAM'])\n"
- " <enum 'Menu'>\n"
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 560** - Core Support for typing module and generic '
- 'types\n'
- ' Introducing "__class_getitem__()", and outlining when '
- 'a\n'
- ' subscription results in "__class_getitem__()" being '
- 'called\n'
- ' instead of "__getitem__()"\n'
- '\n'
- '\n'
- 'Emulating callable objects\n'
- '==========================\n'
- '\n'
- 'object.__call__(self[, args...])\n'
- '\n'
- ' Called when the instance is “called” as a function; if '
- 'this method\n'
- ' is defined, "x(arg1, arg2, ...)" roughly translates to\n'
- ' "type(x).__call__(x, arg1, ...)". The "object" class '
- 'itself does\n'
- ' not provide this method.\n'
- '\n'
- '\n'
- 'Emulating container types\n'
- '=========================\n'
- '\n'
- 'The following methods can be defined to implement container '
- 'objects.\n'
- 'None of them are provided by the "object" class itself. '
- 'Containers\n'
- 'usually are *sequences* (such as "lists" or "tuples") or '
- '*mappings*\n'
- '(like *dictionaries*), but can represent other containers as '
- 'well.\n'
- 'The first set of methods is used either to emulate a '
- 'sequence or to\n'
- 'emulate a mapping; the difference is that for a sequence, '
- 'the\n'
- 'allowable keys should be the integers *k* for which "0 <= k '
- '< N" where\n'
- '*N* is the length of the sequence, or "slice" objects, which '
- 'define a\n'
- 'range of items. It is also recommended that mappings '
- 'provide the\n'
- 'methods "keys()", "values()", "items()", "get()", '
- '"clear()",\n'
- '"setdefault()", "pop()", "popitem()", "copy()", and '
- '"update()"\n'
- 'behaving similar to those for Python’s standard "dictionary" '
- 'objects.\n'
- 'The "collections.abc" module provides a "MutableMapping" '
- '*abstract\n'
- 'base class* to help create those methods from a base set of\n'
- '"__getitem__()", "__setitem__()", "__delitem__()", and '
- '"keys()".\n'
- 'Mutable sequences should provide methods "append()", '
- '"count()",\n'
- '"index()", "extend()", "insert()", "pop()", "remove()", '
- '"reverse()"\n'
- 'and "sort()", like Python standard "list" objects. Finally, '
- 'sequence\n'
- 'types should implement addition (meaning concatenation) and\n'
- 'multiplication (meaning repetition) by defining the methods\n'
- '"__add__()", "__radd__()", "__iadd__()", "__mul__()", '
- '"__rmul__()" and\n'
- '"__imul__()" described below; they should not define other '
- 'numerical\n'
- 'operators. It is recommended that both mappings and '
- 'sequences\n'
- 'implement the "__contains__()" method to allow efficient use '
- 'of the\n'
- '"in" operator; for mappings, "in" should search the '
- 'mapping’s keys;\n'
- 'for sequences, it should search through the values. It is '
- 'further\n'
- 'recommended that both mappings and sequences implement the\n'
- '"__iter__()" method to allow efficient iteration through '
- 'the\n'
- 'container; for mappings, "__iter__()" should iterate through '
- 'the\n'
- 'object’s keys; for sequences, it should iterate through the '
- 'values.\n'
- '\n'
- 'object.__len__(self)\n'
- '\n'
- ' Called to implement the built-in function "len()". '
- 'Should return\n'
- ' the length of the object, an integer ">=" 0. Also, an '
- 'object that\n'
- ' doesn’t define a "__bool__()" method and whose '
- '"__len__()" method\n'
- ' returns zero is considered to be false in a Boolean '
- 'context.\n'
- '\n'
- ' **CPython implementation detail:** In CPython, the length '
- 'is\n'
- ' required to be at most "sys.maxsize". If the length is '
- 'larger than\n'
- ' "sys.maxsize" some features (such as "len()") may raise\n'
- ' "OverflowError". To prevent raising "OverflowError" by '
- 'truth value\n'
- ' testing, an object must define a "__bool__()" method.\n'
- '\n'
- 'object.__length_hint__(self)\n'
- '\n'
- ' Called to implement "operator.length_hint()". Should '
- 'return an\n'
- ' estimated length for the object (which may be greater or '
- 'less than\n'
- ' the actual length). The length must be an integer ">=" 0. '
- 'The\n'
- ' return value may also be "NotImplemented", which is '
- 'treated the\n'
- ' same as if the "__length_hint__" method didn’t exist at '
- 'all. This\n'
- ' method is purely an optimization and is never required '
- 'for\n'
- ' correctness.\n'
- '\n'
- ' Added in version 3.4.\n'
- '\n'
- 'Note:\n'
- '\n'
- ' Slicing is done exclusively with the following three '
- 'methods. A\n'
- ' call like\n'
- '\n'
- ' a[1:2] = b\n'
- '\n'
- ' is translated to\n'
- '\n'
- ' a[slice(1, 2, None)] = b\n'
- '\n'
- ' and so forth. Missing slice items are always filled in '
- 'with "None".\n'
- '\n'
- 'object.__getitem__(self, key)\n'
- '\n'
- ' Called to implement evaluation of "self[key]". For '
- '*sequence*\n'
- ' types, the accepted keys should be integers. Optionally, '
- 'they may\n'
- ' support "slice" objects as well. Negative index support '
- 'is also\n'
- ' optional. If *key* is of an inappropriate type, '
- '"TypeError" may be\n'
- ' raised; if *key* is a value outside the set of indexes '
- 'for the\n'
- ' sequence (after any special interpretation of negative '
- 'values),\n'
- ' "IndexError" should be raised. For *mapping* types, if '
- '*key* is\n'
- ' missing (not in the container), "KeyError" should be '
- 'raised.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' "for" loops expect that an "IndexError" will be raised '
- 'for\n'
- ' illegal indexes to allow proper detection of the end of '
- 'the\n'
- ' sequence.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' When subscripting a *class*, the special class method\n'
- ' "__class_getitem__()" may be called instead of '
- '"__getitem__()".\n'
- ' See __class_getitem__ versus __getitem__ for more '
- 'details.\n'
- '\n'
- 'object.__setitem__(self, key, value)\n'
- '\n'
- ' Called to implement assignment to "self[key]". Same note '
- 'as for\n'
- ' "__getitem__()". This should only be implemented for '
- 'mappings if\n'
- ' the objects support changes to the values for keys, or if '
- 'new keys\n'
- ' can be added, or for sequences if elements can be '
- 'replaced. The\n'
- ' same exceptions should be raised for improper *key* '
- 'values as for\n'
- ' the "__getitem__()" method.\n'
- '\n'
- 'object.__delitem__(self, key)\n'
- '\n'
- ' Called to implement deletion of "self[key]". Same note '
- 'as for\n'
- ' "__getitem__()". This should only be implemented for '
- 'mappings if\n'
- ' the objects support removal of keys, or for sequences if '
- 'elements\n'
- ' can be removed from the sequence. The same exceptions '
- 'should be\n'
- ' raised for improper *key* values as for the '
- '"__getitem__()" method.\n'
- '\n'
- 'object.__missing__(self, key)\n'
- '\n'
- ' Called by "dict"."__getitem__()" to implement "self[key]" '
- 'for dict\n'
- ' subclasses when key is not in the dictionary.\n'
- '\n'
- 'object.__iter__(self)\n'
- '\n'
- ' This method is called when an *iterator* is required for '
- 'a\n'
- ' container. This method should return a new iterator '
- 'object that can\n'
- ' iterate over all the objects in the container. For '
- 'mappings, it\n'
- ' should iterate over the keys of the container.\n'
- '\n'
- 'object.__reversed__(self)\n'
- '\n'
- ' Called (if present) by the "reversed()" built-in to '
- 'implement\n'
- ' reverse iteration. It should return a new iterator '
- 'object that\n'
- ' iterates over all the objects in the container in reverse '
- 'order.\n'
- '\n'
- ' If the "__reversed__()" method is not provided, the '
- '"reversed()"\n'
- ' built-in will fall back to using the sequence protocol '
- '("__len__()"\n'
- ' and "__getitem__()"). Objects that support the sequence '
- 'protocol\n'
- ' should only provide "__reversed__()" if they can provide '
- 'an\n'
- ' implementation that is more efficient than the one '
- 'provided by\n'
- ' "reversed()".\n'
- '\n'
- 'The membership test operators ("in" and "not in") are '
- 'normally\n'
- 'implemented as an iteration through a container. However, '
- 'container\n'
- 'objects can supply the following special method with a more '
- 'efficient\n'
- 'implementation, which also does not require the object be '
- 'iterable.\n'
- '\n'
- 'object.__contains__(self, item)\n'
- '\n'
- ' Called to implement membership test operators. Should '
- 'return true\n'
- ' if *item* is in *self*, false otherwise. For mapping '
- 'objects, this\n'
- ' should consider the keys of the mapping rather than the '
- 'values or\n'
- ' the key-item pairs.\n'
- '\n'
- ' For objects that don’t define "__contains__()", the '
- 'membership test\n'
- ' first tries iteration via "__iter__()", then the old '
- 'sequence\n'
- ' iteration protocol via "__getitem__()", see this section '
- 'in the\n'
- ' language reference.\n'
- '\n'
- '\n'
- 'Emulating numeric types\n'
- '=======================\n'
- '\n'
- 'The following methods can be defined to emulate numeric '
- 'objects.\n'
- 'Methods corresponding to operations that are not supported '
- 'by the\n'
- 'particular kind of number implemented (e.g., bitwise '
- 'operations for\n'
- 'non-integral numbers) should be left undefined.\n'
- '\n'
- 'object.__add__(self, other)\n'
- 'object.__sub__(self, other)\n'
- 'object.__mul__(self, other)\n'
- 'object.__matmul__(self, other)\n'
- 'object.__truediv__(self, other)\n'
- 'object.__floordiv__(self, other)\n'
- 'object.__mod__(self, other)\n'
- 'object.__divmod__(self, other)\n'
- 'object.__pow__(self, other[, modulo])\n'
- 'object.__lshift__(self, other)\n'
- 'object.__rshift__(self, other)\n'
- 'object.__and__(self, other)\n'
- 'object.__xor__(self, other)\n'
- 'object.__or__(self, other)\n'
- '\n'
- ' These methods are called to implement the binary '
- 'arithmetic\n'
- ' operations ("+", "-", "*", "@", "/", "//", "%", '
- '"divmod()",\n'
- ' "pow()", "**", "<<", ">>", "&", "^", "|"). For instance, '
- 'to\n'
- ' evaluate the expression "x + y", where *x* is an instance '
- 'of a\n'
- ' class that has an "__add__()" method, "type(x).__add__(x, '
- 'y)" is\n'
- ' called. The "__divmod__()" method should be the '
- 'equivalent to\n'
- ' using "__floordiv__()" and "__mod__()"; it should not be '
- 'related to\n'
- ' "__truediv__()". Note that "__pow__()" should be defined '
- 'to accept\n'
- ' an optional third argument if the ternary version of the '
- 'built-in\n'
- ' "pow()" function is to be supported.\n'
- '\n'
- ' If one of those methods does not support the operation '
- 'with the\n'
- ' supplied arguments, it should return "NotImplemented".\n'
- '\n'
- 'object.__radd__(self, other)\n'
- 'object.__rsub__(self, other)\n'
- 'object.__rmul__(self, other)\n'
- 'object.__rmatmul__(self, other)\n'
- 'object.__rtruediv__(self, other)\n'
- 'object.__rfloordiv__(self, other)\n'
- 'object.__rmod__(self, other)\n'
- 'object.__rdivmod__(self, other)\n'
- 'object.__rpow__(self, other[, modulo])\n'
- 'object.__rlshift__(self, other)\n'
- 'object.__rrshift__(self, other)\n'
- 'object.__rand__(self, other)\n'
- 'object.__rxor__(self, other)\n'
- 'object.__ror__(self, other)\n'
- '\n'
- ' These methods are called to implement the binary '
- 'arithmetic\n'
- ' operations ("+", "-", "*", "@", "/", "//", "%", '
- '"divmod()",\n'
- ' "pow()", "**", "<<", ">>", "&", "^", "|") with reflected '
- '(swapped)\n'
- ' operands. These functions are only called if the left '
- 'operand does\n'
- ' not support the corresponding operation [3] and the '
- 'operands are of\n'
- ' different types. [4] For instance, to evaluate the '
- 'expression "x -\n'
- ' y", where *y* is an instance of a class that has an '
- '"__rsub__()"\n'
- ' method, "type(y).__rsub__(y, x)" is called if '
- '"type(x).__sub__(x,\n'
- ' y)" returns "NotImplemented".\n'
- '\n'
- ' Note that ternary "pow()" will not try calling '
- '"__rpow__()" (the\n'
- ' coercion rules would become too complicated).\n'
- '\n'
- ' Note:\n'
- '\n'
- ' If the right operand’s type is a subclass of the left '
- 'operand’s\n'
- ' type and that subclass provides a different '
- 'implementation of the\n'
- ' reflected method for the operation, this method will be '
- 'called\n'
- ' before the left operand’s non-reflected method. This '
- 'behavior\n'
- ' allows subclasses to override their ancestors’ '
- 'operations.\n'
- '\n'
- 'object.__iadd__(self, other)\n'
- 'object.__isub__(self, other)\n'
- 'object.__imul__(self, other)\n'
- 'object.__imatmul__(self, other)\n'
- 'object.__itruediv__(self, other)\n'
- 'object.__ifloordiv__(self, other)\n'
- 'object.__imod__(self, other)\n'
- 'object.__ipow__(self, other[, modulo])\n'
- 'object.__ilshift__(self, other)\n'
- 'object.__irshift__(self, other)\n'
- 'object.__iand__(self, other)\n'
- 'object.__ixor__(self, other)\n'
- 'object.__ior__(self, other)\n'
- '\n'
- ' These methods are called to implement the augmented '
- 'arithmetic\n'
- ' assignments ("+=", "-=", "*=", "@=", "/=", "//=", "%=", '
- '"**=",\n'
- ' "<<=", ">>=", "&=", "^=", "|="). These methods should '
- 'attempt to\n'
- ' do the operation in-place (modifying *self*) and return '
- 'the result\n'
- ' (which could be, but does not have to be, *self*). If a '
- 'specific\n'
- ' method is not defined, or if that method returns '
- '"NotImplemented",\n'
- ' the augmented assignment falls back to the normal '
- 'methods. For\n'
- ' instance, if *x* is an instance of a class with an '
- '"__iadd__()"\n'
- ' method, "x += y" is equivalent to "x = x.__iadd__(y)" . '
- 'If\n'
- ' "__iadd__()" does not exist, or if "x.__iadd__(y)" '
- 'returns\n'
- ' "NotImplemented", "x.__add__(y)" and "y.__radd__(x)" are\n'
- ' considered, as with the evaluation of "x + y". In '
- 'certain\n'
- ' situations, augmented assignment can result in unexpected '
- 'errors\n'
- ' (see Why does a_tuple[i] += [‘item’] raise an exception '
- 'when the\n'
- ' addition works?), but this behavior is in fact part of '
- 'the data\n'
- ' model.\n'
- '\n'
- 'object.__neg__(self)\n'
- 'object.__pos__(self)\n'
- 'object.__abs__(self)\n'
- 'object.__invert__(self)\n'
- '\n'
- ' Called to implement the unary arithmetic operations ("-", '
- '"+",\n'
- ' "abs()" and "~").\n'
- '\n'
- 'object.__complex__(self)\n'
- 'object.__int__(self)\n'
- 'object.__float__(self)\n'
- '\n'
- ' Called to implement the built-in functions "complex()", '
- '"int()" and\n'
- ' "float()". Should return a value of the appropriate '
- 'type.\n'
- '\n'
- 'object.__index__(self)\n'
- '\n'
- ' Called to implement "operator.index()", and whenever '
- 'Python needs\n'
- ' to losslessly convert the numeric object to an integer '
- 'object (such\n'
- ' as in slicing, or in the built-in "bin()", "hex()" and '
- '"oct()"\n'
- ' functions). Presence of this method indicates that the '
- 'numeric\n'
- ' object is an integer type. Must return an integer.\n'
- '\n'
- ' If "__int__()", "__float__()" and "__complex__()" are not '
- 'defined\n'
- ' then corresponding built-in functions "int()", "float()" '
- 'and\n'
- ' "complex()" fall back to "__index__()".\n'
- '\n'
- 'object.__round__(self[, ndigits])\n'
- 'object.__trunc__(self)\n'
- 'object.__floor__(self)\n'
- 'object.__ceil__(self)\n'
- '\n'
- ' Called to implement the built-in function "round()" and '
- '"math"\n'
- ' functions "trunc()", "floor()" and "ceil()". Unless '
- '*ndigits* is\n'
- ' passed to "__round__()" all these methods should return '
- 'the value\n'
- ' of the object truncated to an "Integral" (typically an '
- '"int").\n'
- '\n'
- ' The built-in function "int()" falls back to "__trunc__()" '
- 'if\n'
- ' neither "__int__()" nor "__index__()" is defined.\n'
- '\n'
- ' Changed in version 3.11: The delegation of "int()" to '
- '"__trunc__()"\n'
- ' is deprecated.\n'
- '\n'
- '\n'
- 'With Statement Context Managers\n'
- '===============================\n'
- '\n'
- 'A *context manager* is an object that defines the runtime '
- 'context to\n'
- 'be established when executing a "with" statement. The '
- 'context manager\n'
- 'handles the entry into, and the exit from, the desired '
- 'runtime context\n'
- 'for the execution of the block of code. Context managers '
- 'are normally\n'
- 'invoked using the "with" statement (described in section The '
- 'with\n'
- 'statement), but can also be used by directly invoking their '
- 'methods.\n'
- '\n'
- 'Typical uses of context managers include saving and '
- 'restoring various\n'
- 'kinds of global state, locking and unlocking resources, '
- 'closing opened\n'
- 'files, etc.\n'
- '\n'
- 'For more information on context managers, see Context '
- 'Manager Types.\n'
- 'The "object" class itself does not provide the context '
- 'manager\n'
- 'methods.\n'
- '\n'
- 'object.__enter__(self)\n'
- '\n'
- ' Enter the runtime context related to this object. The '
- '"with"\n'
- ' statement will bind this method’s return value to the '
- 'target(s)\n'
- ' specified in the "as" clause of the statement, if any.\n'
- '\n'
- 'object.__exit__(self, exc_type, exc_value, traceback)\n'
- '\n'
- ' Exit the runtime context related to this object. The '
- 'parameters\n'
- ' describe the exception that caused the context to be '
- 'exited. If the\n'
- ' context was exited without an exception, all three '
- 'arguments will\n'
- ' be "None".\n'
- '\n'
- ' If an exception is supplied, and the method wishes to '
- 'suppress the\n'
- ' exception (i.e., prevent it from being propagated), it '
- 'should\n'
- ' return a true value. Otherwise, the exception will be '
- 'processed\n'
- ' normally upon exit from this method.\n'
- '\n'
- ' Note that "__exit__()" methods should not reraise the '
- 'passed-in\n'
- ' exception; this is the caller’s responsibility.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 343** - The “with” statement\n'
- ' The specification, background, and examples for the '
- 'Python "with"\n'
- ' statement.\n'
- '\n'
- '\n'
- 'Customizing positional arguments in class pattern matching\n'
- '==========================================================\n'
- '\n'
- 'When using a class name in a pattern, positional arguments '
- 'in the\n'
- 'pattern are not allowed by default, i.e. "case MyClass(x, '
- 'y)" is\n'
- 'typically invalid without special support in "MyClass". To '
- 'be able to\n'
- 'use that kind of pattern, the class needs to define a '
- '*__match_args__*\n'
- 'attribute.\n'
- '\n'
- 'object.__match_args__\n'
- '\n'
- ' This class variable can be assigned a tuple of strings. '
- 'When this\n'
- ' class is used in a class pattern with positional '
- 'arguments, each\n'
- ' positional argument will be converted into a keyword '
- 'argument,\n'
- ' using the corresponding value in *__match_args__* as the '
- 'keyword.\n'
- ' The absence of this attribute is equivalent to setting it '
- 'to "()".\n'
- '\n'
- 'For example, if "MyClass.__match_args__" is "("left", '
- '"center",\n'
- '"right")" that means that "case MyClass(x, y)" is equivalent '
- 'to "case\n'
- 'MyClass(left=x, center=y)". Note that the number of '
- 'arguments in the\n'
- 'pattern must be smaller than or equal to the number of '
- 'elements in\n'
- '*__match_args__*; if it is larger, the pattern match attempt '
- 'will\n'
- 'raise a "TypeError".\n'
- '\n'
- 'Added in version 3.10.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 634** - Structural Pattern Matching\n'
- ' The specification for the Python "match" statement.\n'
- '\n'
- '\n'
- 'Emulating buffer types\n'
- '======================\n'
- '\n'
- 'The buffer protocol provides a way for Python objects to '
- 'expose\n'
- 'efficient access to a low-level memory array. This protocol '
- 'is\n'
- 'implemented by builtin types such as "bytes" and '
- '"memoryview", and\n'
- 'third-party libraries may define additional buffer types.\n'
- '\n'
- 'While buffer types are usually implemented in C, it is also '
- 'possible\n'
- 'to implement the protocol in Python.\n'
- '\n'
- 'object.__buffer__(self, flags)\n'
- '\n'
- ' Called when a buffer is requested from *self* (for '
- 'example, by the\n'
- ' "memoryview" constructor). The *flags* argument is an '
- 'integer\n'
- ' representing the kind of buffer requested, affecting for '
- 'example\n'
- ' whether the returned buffer is read-only or writable.\n'
- ' "inspect.BufferFlags" provides a convenient way to '
- 'interpret the\n'
- ' flags. The method must return a "memoryview" object.\n'
- '\n'
- 'object.__release_buffer__(self, buffer)\n'
- '\n'
- ' Called when a buffer is no longer needed. The *buffer* '
- 'argument is\n'
- ' a "memoryview" object that was previously returned by\n'
- ' "__buffer__()". The method must release any resources '
- 'associated\n'
- ' with the buffer. This method should return "None". Buffer '
- 'objects\n'
- ' that do not need to perform any cleanup are not required '
- 'to\n'
- ' implement this method.\n'
- '\n'
- 'Added in version 3.12.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 688** - Making the buffer protocol accessible in '
- 'Python\n'
- ' Introduces the Python "__buffer__" and '
- '"__release_buffer__"\n'
- ' methods.\n'
- '\n'
- ' "collections.abc.Buffer"\n'
- ' ABC for buffer types.\n'
- '\n'
- '\n'
- 'Special method lookup\n'
- '=====================\n'
- '\n'
- 'For custom classes, implicit invocations of special methods '
- 'are only\n'
- 'guaranteed to work correctly if defined on an object’s type, '
- 'not in\n'
- 'the object’s instance dictionary. That behaviour is the '
- 'reason why\n'
- 'the following code raises an exception:\n'
- '\n'
- ' >>> class C:\n'
- ' ... pass\n'
- ' ...\n'
- ' >>> c = C()\n'
- ' >>> c.__len__ = lambda: 5\n'
- ' >>> len(c)\n'
- ' Traceback (most recent call last):\n'
- ' File "<stdin>", line 1, in <module>\n'
- " TypeError: object of type 'C' has no len()\n"
- '\n'
- 'The rationale behind this behaviour lies with a number of '
- 'special\n'
- 'methods such as "__hash__()" and "__repr__()" that are '
- 'implemented by\n'
- 'all objects, including type objects. If the implicit lookup '
- 'of these\n'
- 'methods used the conventional lookup process, they would '
- 'fail when\n'
- 'invoked on the type object itself:\n'
- '\n'
- ' >>> 1 .__hash__() == hash(1)\n'
- ' True\n'
- ' >>> int.__hash__() == hash(int)\n'
- ' Traceback (most recent call last):\n'
- ' File "<stdin>", line 1, in <module>\n'
- " TypeError: descriptor '__hash__' of 'int' object needs an "
- 'argument\n'
- '\n'
- 'Incorrectly attempting to invoke an unbound method of a '
- 'class in this\n'
- 'way is sometimes referred to as ‘metaclass confusion’, and '
- 'is avoided\n'
- 'by bypassing the instance when looking up special methods:\n'
- '\n'
- ' >>> type(1).__hash__(1) == hash(1)\n'
- ' True\n'
- ' >>> type(int).__hash__(int) == hash(int)\n'
- ' True\n'
- '\n'
- 'In addition to bypassing any instance attributes in the '
- 'interest of\n'
- 'correctness, implicit special method lookup generally also '
- 'bypasses\n'
- 'the "__getattribute__()" method even of the object’s '
- 'metaclass:\n'
- '\n'
- ' >>> class Meta(type):\n'
- ' ... def __getattribute__(*args):\n'
- ' ... print("Metaclass getattribute invoked")\n'
- ' ... return type.__getattribute__(*args)\n'
- ' ...\n'
- ' >>> class C(object, metaclass=Meta):\n'
- ' ... def __len__(self):\n'
- ' ... return 10\n'
- ' ... def __getattribute__(*args):\n'
- ' ... print("Class getattribute invoked")\n'
- ' ... return object.__getattribute__(*args)\n'
- ' ...\n'
- ' >>> c = C()\n'
- ' >>> c.__len__() # Explicit lookup via '
- 'instance\n'
- ' Class getattribute invoked\n'
- ' 10\n'
- ' >>> type(c).__len__(c) # Explicit lookup via '
- 'type\n'
- ' Metaclass getattribute invoked\n'
- ' 10\n'
- ' >>> len(c) # Implicit lookup\n'
- ' 10\n'
- '\n'
- 'Bypassing the "__getattribute__()" machinery in this fashion '
- 'provides\n'
- 'significant scope for speed optimisations within the '
- 'interpreter, at\n'
- 'the cost of some flexibility in the handling of special '
- 'methods (the\n'
- 'special method *must* be set on the class object itself in '
- 'order to be\n'
- 'consistently invoked by the interpreter).\n',
- 'string-methods': 'String Methods\n'
- '**************\n'
- '\n'
- 'Strings implement all of the common sequence operations, '
- 'along with\n'
- 'the additional methods described below.\n'
- '\n'
- 'Strings also support two styles of string formatting, one '
- 'providing a\n'
- 'large degree of flexibility and customization (see '
- '"str.format()",\n'
- 'Format String Syntax and Custom String Formatting) and the '
- 'other based\n'
- 'on C "printf" style formatting that handles a narrower '
- 'range of types\n'
- 'and is slightly harder to use correctly, but is often '
- 'faster for the\n'
- 'cases it can handle (printf-style String Formatting).\n'
- '\n'
- 'The Text Processing Services section of the standard '
- 'library covers a\n'
- 'number of other modules that provide various text related '
- 'utilities\n'
- '(including regular expression support in the "re" '
- 'module).\n'
- '\n'
- 'str.capitalize()\n'
- '\n'
- ' Return a copy of the string with its first character '
- 'capitalized\n'
- ' and the rest lowercased.\n'
- '\n'
- ' Changed in version 3.8: The first character is now put '
- 'into\n'
- ' titlecase rather than uppercase. This means that '
- 'characters like\n'
- ' digraphs will only have their first letter capitalized, '
- 'instead of\n'
- ' the full character.\n'
- '\n'
- 'str.casefold()\n'
- '\n'
- ' Return a casefolded copy of the string. Casefolded '
- 'strings may be\n'
- ' used for caseless matching.\n'
- '\n'
- ' Casefolding is similar to lowercasing but more '
- 'aggressive because\n'
- ' it is intended to remove all case distinctions in a '
- 'string. For\n'
- ' example, the German lowercase letter "\'ß\'" is '
- 'equivalent to ""ss"".\n'
- ' Since it is already lowercase, "lower()" would do '
- 'nothing to "\'ß\'";\n'
- ' "casefold()" converts it to ""ss"".\n'
- '\n'
- ' The casefolding algorithm is described in section 3.13 '
- '‘Default\n'
- ' Case Folding’ of the Unicode Standard.\n'
- '\n'
- ' Added in version 3.3.\n'
- '\n'
- 'str.center(width[, fillchar])\n'
- '\n'
- ' Return centered in a string of length *width*. Padding '
- 'is done\n'
- ' using the specified *fillchar* (default is an ASCII '
- 'space). The\n'
- ' original string is returned if *width* is less than or '
- 'equal to\n'
- ' "len(s)".\n'
- '\n'
- 'str.count(sub[, start[, end]])\n'
- '\n'
- ' Return the number of non-overlapping occurrences of '
- 'substring *sub*\n'
- ' in the range [*start*, *end*]. Optional arguments '
- '*start* and\n'
- ' *end* are interpreted as in slice notation.\n'
- '\n'
- ' If *sub* is empty, returns the number of empty strings '
- 'between\n'
- ' characters which is the length of the string plus one.\n'
- '\n'
- "str.encode(encoding='utf-8', errors='strict')\n"
- '\n'
- ' Return the string encoded to "bytes".\n'
- '\n'
- ' *encoding* defaults to "\'utf-8\'"; see Standard '
- 'Encodings for\n'
- ' possible values.\n'
- '\n'
- ' *errors* controls how encoding errors are handled. If '
- '"\'strict\'"\n'
- ' (the default), a "UnicodeError" exception is raised. '
- 'Other possible\n'
- ' values are "\'ignore\'", "\'replace\'", '
- '"\'xmlcharrefreplace\'",\n'
- ' "\'backslashreplace\'" and any other name registered '
- 'via\n'
- ' "codecs.register_error()". See Error Handlers for '
- 'details.\n'
- '\n'
- ' For performance reasons, the value of *errors* is not '
- 'checked for\n'
- ' validity unless an encoding error actually occurs, '
- 'Python\n'
- ' Development Mode is enabled or a debug build is used.\n'
- '\n'
- ' Changed in version 3.1: Added support for keyword '
- 'arguments.\n'
- '\n'
- ' Changed in version 3.9: The value of the *errors* '
- 'argument is now\n'
- ' checked in Python Development Mode and in debug mode.\n'
- '\n'
- 'str.endswith(suffix[, start[, end]])\n'
- '\n'
- ' Return "True" if the string ends with the specified '
- '*suffix*,\n'
- ' otherwise return "False". *suffix* can also be a tuple '
- 'of suffixes\n'
- ' to look for. With optional *start*, test beginning at '
- 'that\n'
- ' position. With optional *end*, stop comparing at that '
- 'position.\n'
- '\n'
- 'str.expandtabs(tabsize=8)\n'
- '\n'
- ' Return a copy of the string where all tab characters '
- 'are replaced\n'
- ' by one or more spaces, depending on the current column '
- 'and the\n'
- ' given tab size. Tab positions occur every *tabsize* '
- 'characters\n'
- ' (default is 8, giving tab positions at columns 0, 8, 16 '
- 'and so on).\n'
- ' To expand the string, the current column is set to zero '
- 'and the\n'
- ' string is examined character by character. If the '
- 'character is a\n'
- ' tab ("\\t"), one or more space characters are inserted '
- 'in the result\n'
- ' until the current column is equal to the next tab '
- 'position. (The\n'
- ' tab character itself is not copied.) If the character '
- 'is a newline\n'
- ' ("\\n") or return ("\\r"), it is copied and the current '
- 'column is\n'
- ' reset to zero. Any other character is copied unchanged '
- 'and the\n'
- ' current column is incremented by one regardless of how '
- 'the\n'
- ' character is represented when printed.\n'
- '\n'
- " >>> '01\\t012\\t0123\\t01234'.expandtabs()\n"
- " '01 012 0123 01234'\n"
- " >>> '01\\t012\\t0123\\t01234'.expandtabs(4)\n"
- " '01 012 0123 01234'\n"
- '\n'
- 'str.find(sub[, start[, end]])\n'
- '\n'
- ' Return the lowest index in the string where substring '
- '*sub* is\n'
- ' found within the slice "s[start:end]". Optional '
- 'arguments *start*\n'
- ' and *end* are interpreted as in slice notation. Return '
- '"-1" if\n'
- ' *sub* is not found.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' The "find()" method should be used only if you need '
- 'to know the\n'
- ' position of *sub*. To check if *sub* is a substring '
- 'or not, use\n'
- ' the "in" operator:\n'
- '\n'
- " >>> 'Py' in 'Python'\n"
- ' True\n'
- '\n'
- 'str.format(*args, **kwargs)\n'
- '\n'
- ' Perform a string formatting operation. The string on '
- 'which this\n'
- ' method is called can contain literal text or '
- 'replacement fields\n'
- ' delimited by braces "{}". Each replacement field '
- 'contains either\n'
- ' the numeric index of a positional argument, or the name '
- 'of a\n'
- ' keyword argument. Returns a copy of the string where '
- 'each\n'
- ' replacement field is replaced with the string value of '
- 'the\n'
- ' corresponding argument.\n'
- '\n'
- ' >>> "The sum of 1 + 2 is {0}".format(1+2)\n'
- " 'The sum of 1 + 2 is 3'\n"
- '\n'
- ' See Format String Syntax for a description of the '
- 'various\n'
- ' formatting options that can be specified in format '
- 'strings.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' When formatting a number ("int", "float", "complex",\n'
- ' "decimal.Decimal" and subclasses) with the "n" type '
- '(ex:\n'
- ' "\'{:n}\'.format(1234)"), the function temporarily '
- 'sets the\n'
- ' "LC_CTYPE" locale to the "LC_NUMERIC" locale to '
- 'decode\n'
- ' "decimal_point" and "thousands_sep" fields of '
- '"localeconv()" if\n'
- ' they are non-ASCII or longer than 1 byte, and the '
- '"LC_NUMERIC"\n'
- ' locale is different than the "LC_CTYPE" locale. This '
- 'temporary\n'
- ' change affects other threads.\n'
- '\n'
- ' Changed in version 3.7: When formatting a number with '
- 'the "n" type,\n'
- ' the function sets temporarily the "LC_CTYPE" locale to '
- 'the\n'
- ' "LC_NUMERIC" locale in some cases.\n'
- '\n'
- 'str.format_map(mapping)\n'
- '\n'
- ' Similar to "str.format(**mapping)", except that '
- '"mapping" is used\n'
- ' directly and not copied to a "dict". This is useful if '
- 'for example\n'
- ' "mapping" is a dict subclass:\n'
- '\n'
- ' >>> class Default(dict):\n'
- ' ... def __missing__(self, key):\n'
- ' ... return key\n'
- ' ...\n'
- " >>> '{name} was born in "
- "{country}'.format_map(Default(name='Guido'))\n"
- " 'Guido was born in country'\n"
- '\n'
- ' Added in version 3.2.\n'
- '\n'
- 'str.index(sub[, start[, end]])\n'
- '\n'
- ' Like "find()", but raise "ValueError" when the '
- 'substring is not\n'
- ' found.\n'
- '\n'
- 'str.isalnum()\n'
- '\n'
- ' Return "True" if all characters in the string are '
- 'alphanumeric and\n'
- ' there is at least one character, "False" otherwise. A '
- 'character\n'
- ' "c" is alphanumeric if one of the following returns '
- '"True":\n'
- ' "c.isalpha()", "c.isdecimal()", "c.isdigit()", or '
- '"c.isnumeric()".\n'
- '\n'
- 'str.isalpha()\n'
- '\n'
- ' Return "True" if all characters in the string are '
- 'alphabetic and\n'
- ' there is at least one character, "False" otherwise. '
- 'Alphabetic\n'
- ' characters are those characters defined in the Unicode '
- 'character\n'
- ' database as “Letter”, i.e., those with general category '
- 'property\n'
- ' being one of “Lm”, “Lt”, “Lu”, “Ll”, or “Lo”. Note '
- 'that this is\n'
- ' different from the Alphabetic property defined in the '
- 'section 4.10\n'
- ' ‘Letters, Alphabetic, and Ideographic’ of the Unicode '
- 'Standard.\n'
- '\n'
- 'str.isascii()\n'
- '\n'
- ' Return "True" if the string is empty or all characters '
- 'in the\n'
- ' string are ASCII, "False" otherwise. ASCII characters '
- 'have code\n'
- ' points in the range U+0000-U+007F.\n'
- '\n'
- ' Added in version 3.7.\n'
- '\n'
- 'str.isdecimal()\n'
- '\n'
- ' Return "True" if all characters in the string are '
- 'decimal\n'
- ' characters and there is at least one character, "False" '
- 'otherwise.\n'
- ' Decimal characters are those that can be used to form '
- 'numbers in\n'
- ' base 10, e.g. U+0660, ARABIC-INDIC DIGIT ZERO. '
- 'Formally a decimal\n'
- ' character is a character in the Unicode General '
- 'Category “Nd”.\n'
- '\n'
- 'str.isdigit()\n'
- '\n'
- ' Return "True" if all characters in the string are '
- 'digits and there\n'
- ' is at least one character, "False" otherwise. Digits '
- 'include\n'
- ' decimal characters and digits that need special '
- 'handling, such as\n'
- ' the compatibility superscript digits. This covers '
- 'digits which\n'
- ' cannot be used to form numbers in base 10, like the '
- 'Kharosthi\n'
- ' numbers. Formally, a digit is a character that has the '
- 'property\n'
- ' value Numeric_Type=Digit or Numeric_Type=Decimal.\n'
- '\n'
- 'str.isidentifier()\n'
- '\n'
- ' Return "True" if the string is a valid identifier '
- 'according to the\n'
- ' language definition, section Identifiers and keywords.\n'
- '\n'
- ' "keyword.iskeyword()" can be used to test whether '
- 'string "s" is a\n'
- ' reserved identifier, such as "def" and "class".\n'
- '\n'
- ' Example:\n'
- '\n'
- ' >>> from keyword import iskeyword\n'
- '\n'
- " >>> 'hello'.isidentifier(), iskeyword('hello')\n"
- ' (True, False)\n'
- " >>> 'def'.isidentifier(), iskeyword('def')\n"
- ' (True, True)\n'
- '\n'
- 'str.islower()\n'
- '\n'
- ' Return "True" if all cased characters [4] in the string '
- 'are\n'
- ' lowercase and there is at least one cased character, '
- '"False"\n'
- ' otherwise.\n'
- '\n'
- 'str.isnumeric()\n'
- '\n'
- ' Return "True" if all characters in the string are '
- 'numeric\n'
- ' characters, and there is at least one character, '
- '"False" otherwise.\n'
- ' Numeric characters include digit characters, and all '
- 'characters\n'
- ' that have the Unicode numeric value property, e.g. '
- 'U+2155, VULGAR\n'
- ' FRACTION ONE FIFTH. Formally, numeric characters are '
- 'those with\n'
- ' the property value Numeric_Type=Digit, '
- 'Numeric_Type=Decimal or\n'
- ' Numeric_Type=Numeric.\n'
- '\n'
- 'str.isprintable()\n'
- '\n'
- ' Return "True" if all characters in the string are '
- 'printable or the\n'
- ' string is empty, "False" otherwise. Nonprintable '
- 'characters are\n'
- ' those characters defined in the Unicode character '
- 'database as\n'
- ' “Other” or “Separator”, excepting the ASCII space '
- '(0x20) which is\n'
- ' considered printable. (Note that printable characters '
- 'in this\n'
- ' context are those which should not be escaped when '
- '"repr()" is\n'
- ' invoked on a string. It has no bearing on the handling '
- 'of strings\n'
- ' written to "sys.stdout" or "sys.stderr".)\n'
- '\n'
- 'str.isspace()\n'
- '\n'
- ' Return "True" if there are only whitespace characters '
- 'in the string\n'
- ' and there is at least one character, "False" '
- 'otherwise.\n'
- '\n'
- ' A character is *whitespace* if in the Unicode character '
- 'database\n'
- ' (see "unicodedata"), either its general category is '
- '"Zs"\n'
- ' (“Separator, space”), or its bidirectional class is one '
- 'of "WS",\n'
- ' "B", or "S".\n'
- '\n'
- 'str.istitle()\n'
- '\n'
- ' Return "True" if the string is a titlecased string and '
- 'there is at\n'
- ' least one character, for example uppercase characters '
- 'may only\n'
- ' follow uncased characters and lowercase characters only '
- 'cased ones.\n'
- ' Return "False" otherwise.\n'
- '\n'
- 'str.isupper()\n'
- '\n'
- ' Return "True" if all cased characters [4] in the string '
- 'are\n'
- ' uppercase and there is at least one cased character, '
- '"False"\n'
- ' otherwise.\n'
- '\n'
- " >>> 'BANANA'.isupper()\n"
- ' True\n'
- " >>> 'banana'.isupper()\n"
- ' False\n'
- " >>> 'baNana'.isupper()\n"
- ' False\n'
- " >>> ' '.isupper()\n"
- ' False\n'
- '\n'
- 'str.join(iterable)\n'
- '\n'
- ' Return a string which is the concatenation of the '
- 'strings in\n'
- ' *iterable*. A "TypeError" will be raised if there are '
- 'any non-\n'
- ' string values in *iterable*, including "bytes" '
- 'objects. The\n'
- ' separator between elements is the string providing this '
- 'method.\n'
- '\n'
- 'str.ljust(width[, fillchar])\n'
- '\n'
- ' Return the string left justified in a string of length '
- '*width*.\n'
- ' Padding is done using the specified *fillchar* (default '
- 'is an ASCII\n'
- ' space). The original string is returned if *width* is '
- 'less than or\n'
- ' equal to "len(s)".\n'
- '\n'
- 'str.lower()\n'
- '\n'
- ' Return a copy of the string with all the cased '
- 'characters [4]\n'
- ' converted to lowercase.\n'
- '\n'
- ' The lowercasing algorithm used is described in section '
- '3.13\n'
- ' ‘Default Case Folding’ of the Unicode Standard.\n'
- '\n'
- 'str.lstrip([chars])\n'
- '\n'
- ' Return a copy of the string with leading characters '
- 'removed. The\n'
- ' *chars* argument is a string specifying the set of '
- 'characters to be\n'
- ' removed. If omitted or "None", the *chars* argument '
- 'defaults to\n'
- ' removing whitespace. The *chars* argument is not a '
- 'prefix; rather,\n'
- ' all combinations of its values are stripped:\n'
- '\n'
- " >>> ' spacious '.lstrip()\n"
- " 'spacious '\n"
- " >>> 'www.example.com'.lstrip('cmowz.')\n"
- " 'example.com'\n"
- '\n'
- ' See "str.removeprefix()" for a method that will remove '
- 'a single\n'
- ' prefix string rather than all of a set of characters. '
- 'For example:\n'
- '\n'
- " >>> 'Arthur: three!'.lstrip('Arthur: ')\n"
- " 'ee!'\n"
- " >>> 'Arthur: three!'.removeprefix('Arthur: ')\n"
- " 'three!'\n"
- '\n'
- 'static str.maketrans(x[, y[, z]])\n'
- '\n'
- ' This static method returns a translation table usable '
- 'for\n'
- ' "str.translate()".\n'
- '\n'
- ' If there is only one argument, it must be a dictionary '
- 'mapping\n'
- ' Unicode ordinals (integers) or characters (strings of '
- 'length 1) to\n'
- ' Unicode ordinals, strings (of arbitrary lengths) or '
- '"None".\n'
- ' Character keys will then be converted to ordinals.\n'
- '\n'
- ' If there are two arguments, they must be strings of '
- 'equal length,\n'
- ' and in the resulting dictionary, each character in x '
- 'will be mapped\n'
- ' to the character at the same position in y. If there '
- 'is a third\n'
- ' argument, it must be a string, whose characters will be '
- 'mapped to\n'
- ' "None" in the result.\n'
- '\n'
- 'str.partition(sep)\n'
- '\n'
- ' Split the string at the first occurrence of *sep*, and '
- 'return a\n'
- ' 3-tuple containing the part before the separator, the '
- 'separator\n'
- ' itself, and the part after the separator. If the '
- 'separator is not\n'
- ' found, return a 3-tuple containing the string itself, '
- 'followed by\n'
- ' two empty strings.\n'
- '\n'
- 'str.removeprefix(prefix, /)\n'
- '\n'
- ' If the string starts with the *prefix* string, return\n'
- ' "string[len(prefix):]". Otherwise, return a copy of the '
- 'original\n'
- ' string:\n'
- '\n'
- " >>> 'TestHook'.removeprefix('Test')\n"
- " 'Hook'\n"
- " >>> 'BaseTestCase'.removeprefix('Test')\n"
- " 'BaseTestCase'\n"
- '\n'
- ' Added in version 3.9.\n'
- '\n'
- 'str.removesuffix(suffix, /)\n'
- '\n'
- ' If the string ends with the *suffix* string and that '
- '*suffix* is\n'
- ' not empty, return "string[:-len(suffix)]". Otherwise, '
- 'return a copy\n'
- ' of the original string:\n'
- '\n'
- " >>> 'MiscTests'.removesuffix('Tests')\n"
- " 'Misc'\n"
- " >>> 'TmpDirMixin'.removesuffix('Tests')\n"
- " 'TmpDirMixin'\n"
- '\n'
- ' Added in version 3.9.\n'
- '\n'
- 'str.replace(old, new[, count])\n'
- '\n'
- ' Return a copy of the string with all occurrences of '
- 'substring *old*\n'
- ' replaced by *new*. If the optional argument *count* is '
- 'given, only\n'
- ' the first *count* occurrences are replaced.\n'
- '\n'
- 'str.rfind(sub[, start[, end]])\n'
- '\n'
- ' Return the highest index in the string where substring '
- '*sub* is\n'
- ' found, such that *sub* is contained within '
- '"s[start:end]".\n'
- ' Optional arguments *start* and *end* are interpreted as '
- 'in slice\n'
- ' notation. Return "-1" on failure.\n'
- '\n'
- 'str.rindex(sub[, start[, end]])\n'
- '\n'
- ' Like "rfind()" but raises "ValueError" when the '
- 'substring *sub* is\n'
- ' not found.\n'
- '\n'
- 'str.rjust(width[, fillchar])\n'
- '\n'
- ' Return the string right justified in a string of length '
- '*width*.\n'
- ' Padding is done using the specified *fillchar* (default '
- 'is an ASCII\n'
- ' space). The original string is returned if *width* is '
- 'less than or\n'
- ' equal to "len(s)".\n'
- '\n'
- 'str.rpartition(sep)\n'
- '\n'
- ' Split the string at the last occurrence of *sep*, and '
- 'return a\n'
- ' 3-tuple containing the part before the separator, the '
- 'separator\n'
- ' itself, and the part after the separator. If the '
- 'separator is not\n'
- ' found, return a 3-tuple containing two empty strings, '
- 'followed by\n'
- ' the string itself.\n'
- '\n'
- 'str.rsplit(sep=None, maxsplit=-1)\n'
- '\n'
- ' Return a list of the words in the string, using *sep* '
- 'as the\n'
- ' delimiter string. If *maxsplit* is given, at most '
- '*maxsplit* splits\n'
- ' are done, the *rightmost* ones. If *sep* is not '
- 'specified or\n'
- ' "None", any whitespace string is a separator. Except '
- 'for splitting\n'
- ' from the right, "rsplit()" behaves like "split()" which '
- 'is\n'
- ' described in detail below.\n'
- '\n'
- 'str.rstrip([chars])\n'
- '\n'
- ' Return a copy of the string with trailing characters '
- 'removed. The\n'
- ' *chars* argument is a string specifying the set of '
- 'characters to be\n'
- ' removed. If omitted or "None", the *chars* argument '
- 'defaults to\n'
- ' removing whitespace. The *chars* argument is not a '
- 'suffix; rather,\n'
- ' all combinations of its values are stripped:\n'
- '\n'
- " >>> ' spacious '.rstrip()\n"
- " ' spacious'\n"
- " >>> 'mississippi'.rstrip('ipz')\n"
- " 'mississ'\n"
- '\n'
- ' See "str.removesuffix()" for a method that will remove '
- 'a single\n'
- ' suffix string rather than all of a set of characters. '
- 'For example:\n'
- '\n'
- " >>> 'Monty Python'.rstrip(' Python')\n"
- " 'M'\n"
- " >>> 'Monty Python'.removesuffix(' Python')\n"
- " 'Monty'\n"
- '\n'
- 'str.split(sep=None, maxsplit=-1)\n'
- '\n'
- ' Return a list of the words in the string, using *sep* '
- 'as the\n'
- ' delimiter string. If *maxsplit* is given, at most '
- '*maxsplit*\n'
- ' splits are done (thus, the list will have at most '
- '"maxsplit+1"\n'
- ' elements). If *maxsplit* is not specified or "-1", '
- 'then there is\n'
- ' no limit on the number of splits (all possible splits '
- 'are made).\n'
- '\n'
- ' If *sep* is given, consecutive delimiters are not '
- 'grouped together\n'
- ' and are deemed to delimit empty strings (for example,\n'
- ' "\'1,,2\'.split(\',\')" returns "[\'1\', \'\', '
- '\'2\']"). The *sep* argument\n'
- ' may consist of multiple characters as a single '
- 'delimiter (to split\n'
- ' with multiple delimiters, use "re.split()"). Splitting '
- 'an empty\n'
- ' string with a specified separator returns "[\'\']".\n'
- '\n'
- ' For example:\n'
- '\n'
- " >>> '1,2,3'.split(',')\n"
- " ['1', '2', '3']\n"
- " >>> '1,2,3'.split(',', maxsplit=1)\n"
- " ['1', '2,3']\n"
- " >>> '1,2,,3,'.split(',')\n"
- " ['1', '2', '', '3', '']\n"
- " >>> '1<>2<>3<4'.split('<>')\n"
- " ['1', '2', '3<4']\n"
- '\n'
- ' If *sep* is not specified or is "None", a different '
- 'splitting\n'
- ' algorithm is applied: runs of consecutive whitespace '
- 'are regarded\n'
- ' as a single separator, and the result will contain no '
- 'empty strings\n'
- ' at the start or end if the string has leading or '
- 'trailing\n'
- ' whitespace. Consequently, splitting an empty string or '
- 'a string\n'
- ' consisting of just whitespace with a "None" separator '
- 'returns "[]".\n'
- '\n'
- ' For example:\n'
- '\n'
- " >>> '1 2 3'.split()\n"
- " ['1', '2', '3']\n"
- " >>> '1 2 3'.split(maxsplit=1)\n"
- " ['1', '2 3']\n"
- " >>> ' 1 2 3 '.split()\n"
- " ['1', '2', '3']\n"
- '\n'
- 'str.splitlines(keepends=False)\n'
- '\n'
- ' Return a list of the lines in the string, breaking at '
- 'line\n'
- ' boundaries. Line breaks are not included in the '
- 'resulting list\n'
- ' unless *keepends* is given and true.\n'
- '\n'
- ' This method splits on the following line boundaries. '
- 'In\n'
- ' particular, the boundaries are a superset of *universal '
- 'newlines*.\n'
- '\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- ' | Representation | '
- 'Description |\n'
- ' '
- '|=========================|===============================|\n'
- ' | "\\n" | Line '
- 'Feed |\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- ' | "\\r" | Carriage '
- 'Return |\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- ' | "\\r\\n" | Carriage Return + Line '
- 'Feed |\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- ' | "\\v" or "\\x0b" | Line '
- 'Tabulation |\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- ' | "\\f" or "\\x0c" | Form '
- 'Feed |\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- ' | "\\x1c" | File '
- 'Separator |\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- ' | "\\x1d" | Group '
- 'Separator |\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- ' | "\\x1e" | Record '
- 'Separator |\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- ' | "\\x85" | Next Line (C1 Control '
- 'Code) |\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- ' | "\\u2028" | Line '
- 'Separator |\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- ' | "\\u2029" | Paragraph '
- 'Separator |\n'
- ' '
- '+-------------------------+-------------------------------+\n'
- '\n'
- ' Changed in version 3.2: "\\v" and "\\f" added to list '
- 'of line\n'
- ' boundaries.\n'
- '\n'
- ' For example:\n'
- '\n'
- " >>> 'ab c\\n\\nde fg\\rkl\\r\\n'.splitlines()\n"
- " ['ab c', '', 'de fg', 'kl']\n"
- " >>> 'ab c\\n\\nde "
- "fg\\rkl\\r\\n'.splitlines(keepends=True)\n"
- " ['ab c\\n', '\\n', 'de fg\\r', 'kl\\r\\n']\n"
- '\n'
- ' Unlike "split()" when a delimiter string *sep* is '
- 'given, this\n'
- ' method returns an empty list for the empty string, and '
- 'a terminal\n'
- ' line break does not result in an extra line:\n'
- '\n'
- ' >>> "".splitlines()\n'
- ' []\n'
- ' >>> "One line\\n".splitlines()\n'
- " ['One line']\n"
- '\n'
- ' For comparison, "split(\'\\n\')" gives:\n'
- '\n'
- " >>> ''.split('\\n')\n"
- " ['']\n"
- " >>> 'Two lines\\n'.split('\\n')\n"
- " ['Two lines', '']\n"
- '\n'
- 'str.startswith(prefix[, start[, end]])\n'
- '\n'
- ' Return "True" if string starts with the *prefix*, '
- 'otherwise return\n'
- ' "False". *prefix* can also be a tuple of prefixes to '
- 'look for.\n'
- ' With optional *start*, test string beginning at that '
- 'position.\n'
- ' With optional *end*, stop comparing string at that '
- 'position.\n'
- '\n'
- 'str.strip([chars])\n'
- '\n'
- ' Return a copy of the string with the leading and '
- 'trailing\n'
- ' characters removed. The *chars* argument is a string '
- 'specifying the\n'
- ' set of characters to be removed. If omitted or "None", '
- 'the *chars*\n'
- ' argument defaults to removing whitespace. The *chars* '
- 'argument is\n'
- ' not a prefix or suffix; rather, all combinations of its '
- 'values are\n'
- ' stripped:\n'
- '\n'
- " >>> ' spacious '.strip()\n"
- " 'spacious'\n"
- " >>> 'www.example.com'.strip('cmowz.')\n"
- " 'example'\n"
- '\n'
- ' The outermost leading and trailing *chars* argument '
- 'values are\n'
- ' stripped from the string. Characters are removed from '
- 'the leading\n'
- ' end until reaching a string character that is not '
- 'contained in the\n'
- ' set of characters in *chars*. A similar action takes '
- 'place on the\n'
- ' trailing end. For example:\n'
- '\n'
- " >>> comment_string = '#....... Section 3.2.1 Issue "
- "#32 .......'\n"
- " >>> comment_string.strip('.#! ')\n"
- " 'Section 3.2.1 Issue #32'\n"
- '\n'
- 'str.swapcase()\n'
- '\n'
- ' Return a copy of the string with uppercase characters '
- 'converted to\n'
- ' lowercase and vice versa. Note that it is not '
- 'necessarily true that\n'
- ' "s.swapcase().swapcase() == s".\n'
- '\n'
- 'str.title()\n'
- '\n'
- ' Return a titlecased version of the string where words '
- 'start with an\n'
- ' uppercase character and the remaining characters are '
- 'lowercase.\n'
- '\n'
- ' For example:\n'
- '\n'
- " >>> 'Hello world'.title()\n"
- " 'Hello World'\n"
- '\n'
- ' The algorithm uses a simple language-independent '
- 'definition of a\n'
- ' word as groups of consecutive letters. The definition '
- 'works in\n'
- ' many contexts but it means that apostrophes in '
- 'contractions and\n'
- ' possessives form word boundaries, which may not be the '
- 'desired\n'
- ' result:\n'
- '\n'
- ' >>> "they\'re bill\'s friends from the UK".title()\n'
- ' "They\'Re Bill\'S Friends From The Uk"\n'
- '\n'
- ' The "string.capwords()" function does not have this '
- 'problem, as it\n'
- ' splits words on spaces only.\n'
- '\n'
- ' Alternatively, a workaround for apostrophes can be '
- 'constructed\n'
- ' using regular expressions:\n'
- '\n'
- ' >>> import re\n'
- ' >>> def titlecase(s):\n'
- ' ... return re.sub(r"[A-Za-z]+(\'[A-Za-z]+)?",\n'
- ' ... lambda mo: '
- 'mo.group(0).capitalize(),\n'
- ' ... s)\n'
- ' ...\n'
- ' >>> titlecase("they\'re bill\'s friends.")\n'
- ' "They\'re Bill\'s Friends."\n'
- '\n'
- 'str.translate(table)\n'
- '\n'
- ' Return a copy of the string in which each character has '
- 'been mapped\n'
- ' through the given translation table. The table must be '
- 'an object\n'
- ' that implements indexing via "__getitem__()", typically '
- 'a *mapping*\n'
- ' or *sequence*. When indexed by a Unicode ordinal (an '
- 'integer), the\n'
- ' table object can do any of the following: return a '
- 'Unicode ordinal\n'
- ' or a string, to map the character to one or more other '
- 'characters;\n'
- ' return "None", to delete the character from the return '
- 'string; or\n'
- ' raise a "LookupError" exception, to map the character '
- 'to itself.\n'
- '\n'
- ' You can use "str.maketrans()" to create a translation '
- 'map from\n'
- ' character-to-character mappings in different formats.\n'
- '\n'
- ' See also the "codecs" module for a more flexible '
- 'approach to custom\n'
- ' character mappings.\n'
- '\n'
- 'str.upper()\n'
- '\n'
- ' Return a copy of the string with all the cased '
- 'characters [4]\n'
- ' converted to uppercase. Note that '
- '"s.upper().isupper()" might be\n'
- ' "False" if "s" contains uncased characters or if the '
- 'Unicode\n'
- ' category of the resulting character(s) is not “Lu” '
- '(Letter,\n'
- ' uppercase), but e.g. “Lt” (Letter, titlecase).\n'
- '\n'
- ' The uppercasing algorithm used is described in section '
- '3.13\n'
- ' ‘Default Case Folding’ of the Unicode Standard.\n'
- '\n'
- 'str.zfill(width)\n'
- '\n'
- ' Return a copy of the string left filled with ASCII '
- '"\'0\'" digits to\n'
- ' make a string of length *width*. A leading sign prefix\n'
- ' ("\'+\'"/"\'-\'") is handled by inserting the padding '
- '*after* the sign\n'
- ' character rather than before. The original string is '
- 'returned if\n'
- ' *width* is less than or equal to "len(s)".\n'
- '\n'
- ' For example:\n'
- '\n'
- ' >>> "42".zfill(5)\n'
- " '00042'\n"
- ' >>> "-42".zfill(5)\n'
- " '-0042'\n",
- 'strings': 'String and Bytes literals\n'
- '*************************\n'
- '\n'
- 'String literals are described by the following lexical '
- 'definitions:\n'
- '\n'
- ' stringliteral ::= [stringprefix](shortstring | longstring)\n'
- ' stringprefix ::= "r" | "u" | "R" | "U" | "f" | "F"\n'
- ' | "fr" | "Fr" | "fR" | "FR" | "rf" | "rF" | '
- '"Rf" | "RF"\n'
- ' shortstring ::= "\'" shortstringitem* "\'" | \'"\' '
- 'shortstringitem* \'"\'\n'
- ' longstring ::= "\'\'\'" longstringitem* "\'\'\'" | '
- '\'"""\' longstringitem* \'"""\'\n'
- ' shortstringitem ::= shortstringchar | stringescapeseq\n'
- ' longstringitem ::= longstringchar | stringescapeseq\n'
- ' shortstringchar ::= <any source character except "\\" or '
- 'newline or the quote>\n'
- ' longstringchar ::= <any source character except "\\">\n'
- ' stringescapeseq ::= "\\" <any source character>\n'
- '\n'
- ' bytesliteral ::= bytesprefix(shortbytes | longbytes)\n'
- ' bytesprefix ::= "b" | "B" | "br" | "Br" | "bR" | "BR" | '
- '"rb" | "rB" | "Rb" | "RB"\n'
- ' shortbytes ::= "\'" shortbytesitem* "\'" | \'"\' '
- 'shortbytesitem* \'"\'\n'
- ' longbytes ::= "\'\'\'" longbytesitem* "\'\'\'" | \'"""\' '
- 'longbytesitem* \'"""\'\n'
- ' shortbytesitem ::= shortbyteschar | bytesescapeseq\n'
- ' longbytesitem ::= longbyteschar | bytesescapeseq\n'
- ' shortbyteschar ::= <any ASCII character except "\\" or newline '
- 'or the quote>\n'
- ' longbyteschar ::= <any ASCII character except "\\">\n'
- ' bytesescapeseq ::= "\\" <any ASCII character>\n'
- '\n'
- 'One syntactic restriction not indicated by these productions is '
- 'that\n'
- 'whitespace is not allowed between the "stringprefix" or '
- '"bytesprefix"\n'
- 'and the rest of the literal. The source character set is defined '
- 'by\n'
- 'the encoding declaration; it is UTF-8 if no encoding declaration '
- 'is\n'
- 'given in the source file; see section Encoding declarations.\n'
- '\n'
- 'In plain English: Both types of literals can be enclosed in '
- 'matching\n'
- 'single quotes ("\'") or double quotes ("""). They can also be '
- 'enclosed\n'
- 'in matching groups of three single or double quotes (these are\n'
- 'generally referred to as *triple-quoted strings*). The backslash '
- '("\\")\n'
- 'character is used to give special meaning to otherwise ordinary\n'
- 'characters like "n", which means ‘newline’ when escaped ("\\n"). '
- 'It can\n'
- 'also be used to escape characters that otherwise have a special\n'
- 'meaning, such as newline, backslash itself, or the quote '
- 'character.\n'
- 'See escape sequences below for examples.\n'
- '\n'
- 'Bytes literals are always prefixed with "\'b\'" or "\'B\'"; they '
- 'produce\n'
- 'an instance of the "bytes" type instead of the "str" type. They '
- 'may\n'
- 'only contain ASCII characters; bytes with a numeric value of 128 '
- 'or\n'
- 'greater must be expressed with escapes.\n'
- '\n'
- 'Both string and bytes literals may optionally be prefixed with a\n'
- 'letter "\'r\'" or "\'R\'"; such constructs are called *raw '
- 'string\n'
- 'literals* and *raw bytes literals* respectively and treat '
- 'backslashes\n'
- 'as literal characters. As a result, in raw string literals, '
- '"\'\\U\'"\n'
- 'and "\'\\u\'" escapes are not treated specially.\n'
- '\n'
- 'Added in version 3.3: The "\'rb\'" prefix of raw bytes literals '
- 'has been\n'
- 'added as a synonym of "\'br\'".Support for the unicode legacy '
- 'literal\n'
- '("u\'value\'") was reintroduced to simplify the maintenance of '
- 'dual\n'
- 'Python 2.x and 3.x codebases. See **PEP 414** for more '
- 'information.\n'
- '\n'
- 'A string literal with "\'f\'" or "\'F\'" in its prefix is a '
- '*formatted\n'
- 'string literal*; see f-strings. The "\'f\'" may be combined with '
- '"\'r\'",\n'
- 'but not with "\'b\'" or "\'u\'", therefore raw formatted strings '
- 'are\n'
- 'possible, but formatted bytes literals are not.\n'
- '\n'
- 'In triple-quoted literals, unescaped newlines and quotes are '
- 'allowed\n'
- '(and are retained), except that three unescaped quotes in a row\n'
- 'terminate the literal. (A “quote” is the character used to open '
- 'the\n'
- 'literal, i.e. either "\'" or """.)\n'
- '\n'
- '\n'
- 'Escape sequences\n'
- '================\n'
- '\n'
- 'Unless an "\'r\'" or "\'R\'" prefix is present, escape sequences '
- 'in string\n'
- 'and bytes literals are interpreted according to rules similar to '
- 'those\n'
- 'used by Standard C. The recognized escape sequences are:\n'
- '\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| Escape Sequence | Meaning | '
- 'Notes |\n'
- '|===========================|===================================|=========|\n'
- '| "\\"<newline> | Backslash and newline ignored '
- '| (1) |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\\\" | Backslash '
- '("\\") | |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\\'" | Single quote '
- '("\'") | |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\"" | Double quote (""") '
- '| |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\a" | ASCII Bell (BEL) '
- '| |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\b" | ASCII Backspace (BS) '
- '| |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\f" | ASCII Formfeed (FF) '
- '| |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\n" | ASCII Linefeed (LF) '
- '| |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\r" | ASCII Carriage Return (CR) '
- '| |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\t" | ASCII Horizontal Tab (TAB) '
- '| |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\v" | ASCII Vertical Tab (VT) '
- '| |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\*ooo*" | Character with octal value *ooo* '
- '| (2,4) |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\x*hh*" | Character with hex value *hh* '
- '| (3,4) |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '\n'
- 'Escape sequences only recognized in string literals are:\n'
- '\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| Escape Sequence | Meaning | '
- 'Notes |\n'
- '|===========================|===================================|=========|\n'
- '| "\\N{*name*}" | Character named *name* in the '
- '| (5) |\n'
- '| | Unicode database '
- '| |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\u*xxxx*" | Character with 16-bit hex value '
- '| (6) |\n'
- '| | *xxxx* '
- '| |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '| "\\U*xxxxxxxx*" | Character with 32-bit hex value '
- '| (7) |\n'
- '| | *xxxxxxxx* '
- '| |\n'
- '+---------------------------+-----------------------------------+---------+\n'
- '\n'
- 'Notes:\n'
- '\n'
- '1. A backslash can be added at the end of a line to ignore the\n'
- ' newline:\n'
- '\n'
- " >>> 'This string will not include \\\n"
- " ... backslashes or newline characters.'\n"
- " 'This string will not include backslashes or newline "
- "characters.'\n"
- '\n'
- ' The same result can be achieved using triple-quoted strings, '
- 'or\n'
- ' parentheses and string literal concatenation.\n'
- '\n'
- '2. As in Standard C, up to three octal digits are accepted.\n'
- '\n'
- ' Changed in version 3.11: Octal escapes with value larger than\n'
- ' "0o377" produce a "DeprecationWarning".\n'
- '\n'
- ' Changed in version 3.12: Octal escapes with value larger than\n'
- ' "0o377" produce a "SyntaxWarning". In a future Python version '
- 'they\n'
- ' will be eventually a "SyntaxError".\n'
- '\n'
- '3. Unlike in Standard C, exactly two hex digits are required.\n'
- '\n'
- '4. In a bytes literal, hexadecimal and octal escapes denote the '
- 'byte\n'
- ' with the given value. In a string literal, these escapes '
- 'denote a\n'
- ' Unicode character with the given value.\n'
- '\n'
- '5. Changed in version 3.3: Support for name aliases [1] has been\n'
- ' added.\n'
- '\n'
- '6. Exactly four hex digits are required.\n'
- '\n'
- '7. Any Unicode character can be encoded this way. Exactly eight '
- 'hex\n'
- ' digits are required.\n'
- '\n'
- 'Unlike Standard C, all unrecognized escape sequences are left in '
- 'the\n'
- 'string unchanged, i.e., *the backslash is left in the result*. '
- '(This\n'
- 'behavior is useful when debugging: if an escape sequence is '
- 'mistyped,\n'
- 'the resulting output is more easily recognized as broken.) It is '
- 'also\n'
- 'important to note that the escape sequences only recognized in '
- 'string\n'
- 'literals fall into the category of unrecognized escapes for '
- 'bytes\n'
- 'literals.\n'
- '\n'
- 'Changed in version 3.6: Unrecognized escape sequences produce a\n'
- '"DeprecationWarning".\n'
- '\n'
- 'Changed in version 3.12: Unrecognized escape sequences produce a\n'
- '"SyntaxWarning". In a future Python version they will be '
- 'eventually a\n'
- '"SyntaxError".\n'
- '\n'
- 'Even in a raw literal, quotes can be escaped with a backslash, '
- 'but the\n'
- 'backslash remains in the result; for example, "r"\\""" is a '
- 'valid\n'
- 'string literal consisting of two characters: a backslash and a '
- 'double\n'
- 'quote; "r"\\"" is not a valid string literal (even a raw string '
- 'cannot\n'
- 'end in an odd number of backslashes). Specifically, *a raw '
- 'literal\n'
- 'cannot end in a single backslash* (since the backslash would '
- 'escape\n'
- 'the following quote character). Note also that a single '
- 'backslash\n'
- 'followed by a newline is interpreted as those two characters as '
- 'part\n'
- 'of the literal, *not* as a line continuation.\n',
- 'subscriptions': 'Subscriptions\n'
- '*************\n'
- '\n'
- 'The subscription of an instance of a container class will '
- 'generally\n'
- 'select an element from the container. The subscription of a '
- '*generic\n'
- 'class* will generally return a GenericAlias object.\n'
- '\n'
- ' subscription ::= primary "[" flexible_expression_list '
- '"]"\n'
- '\n'
- 'When an object is subscripted, the interpreter will '
- 'evaluate the\n'
- 'primary and the expression list.\n'
- '\n'
- 'The primary must evaluate to an object that supports '
- 'subscription. An\n'
- 'object may support subscription through defining one or '
- 'both of\n'
- '"__getitem__()" and "__class_getitem__()". When the primary '
- 'is\n'
- 'subscripted, the evaluated result of the expression list '
- 'will be\n'
- 'passed to one of these methods. For more details on when\n'
- '"__class_getitem__" is called instead of "__getitem__", '
- 'see\n'
- '__class_getitem__ versus __getitem__.\n'
- '\n'
- 'If the expression list contains at least one comma, or if '
- 'any of the\n'
- 'expressions are starred, the expression list will evaluate '
- 'to a\n'
- '"tuple" containing the items of the expression list. '
- 'Otherwise, the\n'
- 'expression list will evaluate to the value of the list’s '
- 'sole member.\n'
- '\n'
- 'Changed in version 3.11: Expressions in an expression list '
- 'may be\n'
- 'starred. See **PEP 646**.\n'
- '\n'
- 'For built-in objects, there are two types of objects that '
- 'support\n'
- 'subscription via "__getitem__()":\n'
- '\n'
- '1. Mappings. If the primary is a *mapping*, the expression '
- 'list must\n'
- ' evaluate to an object whose value is one of the keys of '
- 'the\n'
- ' mapping, and the subscription selects the value in the '
- 'mapping that\n'
- ' corresponds to that key. An example of a builtin mapping '
- 'class is\n'
- ' the "dict" class.\n'
- '\n'
- '2. Sequences. If the primary is a *sequence*, the '
- 'expression list must\n'
- ' evaluate to an "int" or a "slice" (as discussed in the '
- 'following\n'
- ' section). Examples of builtin sequence classes include '
- 'the "str",\n'
- ' "list" and "tuple" classes.\n'
- '\n'
- 'The formal syntax makes no special provision for negative '
- 'indices in\n'
- '*sequences*. However, built-in sequences all provide a '
- '"__getitem__()"\n'
- 'method that interprets negative indices by adding the '
- 'length of the\n'
- 'sequence to the index so that, for example, "x[-1]" selects '
- 'the last\n'
- 'item of "x". The resulting value must be a nonnegative '
- 'integer less\n'
- 'than the number of items in the sequence, and the '
- 'subscription selects\n'
- 'the item whose index is that value (counting from zero). '
- 'Since the\n'
- 'support for negative indices and slicing occurs in the '
- 'object’s\n'
- '"__getitem__()" method, subclasses overriding this method '
- 'will need to\n'
- 'explicitly add that support.\n'
- '\n'
- 'A "string" is a special kind of sequence whose items are '
- '*characters*.\n'
- 'A character is not a separate data type but a string of '
- 'exactly one\n'
- 'character.\n',
- 'truth': 'Truth Value Testing\n'
- '*******************\n'
- '\n'
- 'Any object can be tested for truth value, for use in an "if" or\n'
- '"while" condition or as operand of the Boolean operations below.\n'
- '\n'
- 'By default, an object is considered true unless its class defines\n'
- 'either a "__bool__()" method that returns "False" or a "__len__()"\n'
- 'method that returns zero, when called with the object. [1] Here '
- 'are\n'
- 'most of the built-in objects considered false:\n'
- '\n'
- '* constants defined to be false: "None" and "False"\n'
- '\n'
- '* zero of any numeric type: "0", "0.0", "0j", "Decimal(0)",\n'
- ' "Fraction(0, 1)"\n'
- '\n'
- '* empty sequences and collections: "\'\'", "()", "[]", "{}", '
- '"set()",\n'
- ' "range(0)"\n'
- '\n'
- 'Operations and built-in functions that have a Boolean result '
- 'always\n'
- 'return "0" or "False" for false and "1" or "True" for true, unless\n'
- 'otherwise stated. (Important exception: the Boolean operations '
- '"or"\n'
- 'and "and" always return one of their operands.)\n',
- 'try': 'The "try" statement\n'
- '*******************\n'
- '\n'
- 'The "try" statement specifies exception handlers and/or cleanup code\n'
- 'for a group of statements:\n'
- '\n'
- ' try_stmt ::= try1_stmt | try2_stmt | try3_stmt\n'
- ' try1_stmt ::= "try" ":" suite\n'
- ' ("except" [expression ["as" identifier]] ":" '
- 'suite)+\n'
- ' ["else" ":" suite]\n'
- ' ["finally" ":" suite]\n'
- ' try2_stmt ::= "try" ":" suite\n'
- ' ("except" "*" expression ["as" identifier] ":" '
- 'suite)+\n'
- ' ["else" ":" suite]\n'
- ' ["finally" ":" suite]\n'
- ' try3_stmt ::= "try" ":" suite\n'
- ' "finally" ":" suite\n'
- '\n'
- 'Additional information on exceptions can be found in section\n'
- 'Exceptions, and information on using the "raise" statement to '
- 'generate\n'
- 'exceptions may be found in section The raise statement.\n'
- '\n'
- '\n'
- '"except" clause\n'
- '===============\n'
- '\n'
- 'The "except" clause(s) specify one or more exception handlers. When '
- 'no\n'
- 'exception occurs in the "try" clause, no exception handler is\n'
- 'executed. When an exception occurs in the "try" suite, a search for '
- 'an\n'
- 'exception handler is started. This search inspects the "except"\n'
- 'clauses in turn until one is found that matches the exception. An\n'
- 'expression-less "except" clause, if present, must be last; it '
- 'matches\n'
- 'any exception.\n'
- '\n'
- 'For an "except" clause with an expression, the expression must\n'
- 'evaluate to an exception type or a tuple of exception types. The\n'
- 'raised exception matches an "except" clause whose expression '
- 'evaluates\n'
- 'to the class or a *non-virtual base class* of the exception object, '
- 'or\n'
- 'to a tuple that contains such a class.\n'
- '\n'
- 'If no "except" clause matches the exception, the search for an\n'
- 'exception handler continues in the surrounding code and on the\n'
- 'invocation stack. [1]\n'
- '\n'
- 'If the evaluation of an expression in the header of an "except" '
- 'clause\n'
- 'raises an exception, the original search for a handler is canceled '
- 'and\n'
- 'a search starts for the new exception in the surrounding code and on\n'
- 'the call stack (it is treated as if the entire "try" statement '
- 'raised\n'
- 'the exception).\n'
- '\n'
- 'When a matching "except" clause is found, the exception is assigned '
- 'to\n'
- 'the target specified after the "as" keyword in that "except" clause,\n'
- 'if present, and the "except" clause’s suite is executed. All '
- '"except"\n'
- 'clauses must have an executable block. When the end of this block is\n'
- 'reached, execution continues normally after the entire "try"\n'
- 'statement. (This means that if two nested handlers exist for the '
- 'same\n'
- 'exception, and the exception occurs in the "try" clause of the inner\n'
- 'handler, the outer handler will not handle the exception.)\n'
- '\n'
- 'When an exception has been assigned using "as target", it is cleared\n'
- 'at the end of the "except" clause. This is as if\n'
- '\n'
- ' except E as N:\n'
- ' foo\n'
- '\n'
- 'was translated to\n'
- '\n'
- ' except E as N:\n'
- ' try:\n'
- ' foo\n'
- ' finally:\n'
- ' del N\n'
- '\n'
- 'This means the exception must be assigned to a different name to be\n'
- 'able to refer to it after the "except" clause. Exceptions are '
- 'cleared\n'
- 'because with the traceback attached to them, they form a reference\n'
- 'cycle with the stack frame, keeping all locals in that frame alive\n'
- 'until the next garbage collection occurs.\n'
- '\n'
- 'Before an "except" clause’s suite is executed, the exception is '
- 'stored\n'
- 'in the "sys" module, where it can be accessed from within the body '
- 'of\n'
- 'the "except" clause by calling "sys.exception()". When leaving an\n'
- 'exception handler, the exception stored in the "sys" module is reset\n'
- 'to its previous value:\n'
- '\n'
- ' >>> print(sys.exception())\n'
- ' None\n'
- ' >>> try:\n'
- ' ... raise TypeError\n'
- ' ... except:\n'
- ' ... print(repr(sys.exception()))\n'
- ' ... try:\n'
- ' ... raise ValueError\n'
- ' ... except:\n'
- ' ... print(repr(sys.exception()))\n'
- ' ... print(repr(sys.exception()))\n'
- ' ...\n'
- ' TypeError()\n'
- ' ValueError()\n'
- ' TypeError()\n'
- ' >>> print(sys.exception())\n'
- ' None\n'
- '\n'
- '\n'
- '"except*" clause\n'
- '================\n'
- '\n'
- 'The "except*" clause(s) are used for handling "ExceptionGroup"s. The\n'
- 'exception type for matching is interpreted as in the case of '
- '"except",\n'
- 'but in the case of exception groups we can have partial matches when\n'
- 'the type matches some of the exceptions in the group. This means '
- 'that\n'
- 'multiple "except*" clauses can execute, each handling part of the\n'
- 'exception group. Each clause executes at most once and handles an\n'
- 'exception group of all matching exceptions. Each exception in the\n'
- 'group is handled by at most one "except*" clause, the first that\n'
- 'matches it.\n'
- '\n'
- ' >>> try:\n'
- ' ... raise ExceptionGroup("eg",\n'
- ' ... [ValueError(1), TypeError(2), OSError(3), '
- 'OSError(4)])\n'
- ' ... except* TypeError as e:\n'
- " ... print(f'caught {type(e)} with nested {e.exceptions}')\n"
- ' ... except* OSError as e:\n'
- " ... print(f'caught {type(e)} with nested {e.exceptions}')\n"
- ' ...\n'
- " caught <class 'ExceptionGroup'> with nested (TypeError(2),)\n"
- " caught <class 'ExceptionGroup'> with nested (OSError(3), "
- 'OSError(4))\n'
- ' + Exception Group Traceback (most recent call last):\n'
- ' | File "<stdin>", line 2, in <module>\n'
- ' | ExceptionGroup: eg\n'
- ' +-+---------------- 1 ----------------\n'
- ' | ValueError: 1\n'
- ' +------------------------------------\n'
- '\n'
- 'Any remaining exceptions that were not handled by any "except*" '
- 'clause\n'
- 'are re-raised at the end, along with all exceptions that were raised\n'
- 'from within the "except*" clauses. If this list contains more than '
- 'one\n'
- 'exception to reraise, they are combined into an exception group.\n'
- '\n'
- 'If the raised exception is not an exception group and its type '
- 'matches\n'
- 'one of the "except*" clauses, it is caught and wrapped by an '
- 'exception\n'
- 'group with an empty message string.\n'
- '\n'
- ' >>> try:\n'
- ' ... raise BlockingIOError\n'
- ' ... except* BlockingIOError as e:\n'
- ' ... print(repr(e))\n'
- ' ...\n'
- " ExceptionGroup('', (BlockingIOError()))\n"
- '\n'
- 'An "except*" clause must have a matching expression; it cannot be\n'
- '"except*:". Furthermore, this expression cannot contain exception\n'
- 'group types, because that would have ambiguous semantics.\n'
- '\n'
- 'It is not possible to mix "except" and "except*" in the same "try".\n'
- '"break", "continue" and "return" cannot appear in an "except*" '
- 'clause.\n'
- '\n'
- '\n'
- '"else" clause\n'
- '=============\n'
- '\n'
- 'The optional "else" clause is executed if the control flow leaves '
- 'the\n'
- '"try" suite, no exception was raised, and no "return", "continue", '
- 'or\n'
- '"break" statement was executed. Exceptions in the "else" clause are\n'
- 'not handled by the preceding "except" clauses.\n'
- '\n'
- '\n'
- '"finally" clause\n'
- '================\n'
- '\n'
- 'If "finally" is present, it specifies a ‘cleanup’ handler. The '
- '"try"\n'
- 'clause is executed, including any "except" and "else" clauses. If '
- 'an\n'
- 'exception occurs in any of the clauses and is not handled, the\n'
- 'exception is temporarily saved. The "finally" clause is executed. '
- 'If\n'
- 'there is a saved exception it is re-raised at the end of the '
- '"finally"\n'
- 'clause. If the "finally" clause raises another exception, the saved\n'
- 'exception is set as the context of the new exception. If the '
- '"finally"\n'
- 'clause executes a "return", "break" or "continue" statement, the '
- 'saved\n'
- 'exception is discarded:\n'
- '\n'
- ' >>> def f():\n'
- ' ... try:\n'
- ' ... 1/0\n'
- ' ... finally:\n'
- ' ... return 42\n'
- ' ...\n'
- ' >>> f()\n'
- ' 42\n'
- '\n'
- 'The exception information is not available to the program during\n'
- 'execution of the "finally" clause.\n'
- '\n'
- 'When a "return", "break" or "continue" statement is executed in the\n'
- '"try" suite of a "try"…"finally" statement, the "finally" clause is\n'
- 'also executed ‘on the way out.’\n'
- '\n'
- 'The return value of a function is determined by the last "return"\n'
- 'statement executed. Since the "finally" clause always executes, a\n'
- '"return" statement executed in the "finally" clause will always be '
- 'the\n'
- 'last one executed:\n'
- '\n'
- ' >>> def foo():\n'
- ' ... try:\n'
- " ... return 'try'\n"
- ' ... finally:\n'
- " ... return 'finally'\n"
- ' ...\n'
- ' >>> foo()\n'
- " 'finally'\n"
- '\n'
- 'Changed in version 3.8: Prior to Python 3.8, a "continue" statement\n'
- 'was illegal in the "finally" clause due to a problem with the\n'
- 'implementation.\n',
- 'types': 'The standard type hierarchy\n'
- '***************************\n'
- '\n'
- 'Below is a list of the types that are built into Python. '
- 'Extension\n'
- 'modules (written in C, Java, or other languages, depending on the\n'
- 'implementation) can define additional types. Future versions of\n'
- 'Python may add types to the type hierarchy (e.g., rational '
- 'numbers,\n'
- 'efficiently stored arrays of integers, etc.), although such '
- 'additions\n'
- 'will often be provided via the standard library instead.\n'
- '\n'
- 'Some of the type descriptions below contain a paragraph listing\n'
- '‘special attributes.’ These are attributes that provide access to '
- 'the\n'
- 'implementation and are not intended for general use. Their '
- 'definition\n'
- 'may change in the future.\n'
- '\n'
- '\n'
- 'None\n'
- '====\n'
- '\n'
- 'This type has a single value. There is a single object with this\n'
- 'value. This object is accessed through the built-in name "None". It '
- 'is\n'
- 'used to signify the absence of a value in many situations, e.g., it '
- 'is\n'
- 'returned from functions that don’t explicitly return anything. Its\n'
- 'truth value is false.\n'
- '\n'
- '\n'
- 'NotImplemented\n'
- '==============\n'
- '\n'
- 'This type has a single value. There is a single object with this\n'
- 'value. This object is accessed through the built-in name\n'
- '"NotImplemented". Numeric methods and rich comparison methods '
- 'should\n'
- 'return this value if they do not implement the operation for the\n'
- 'operands provided. (The interpreter will then try the reflected\n'
- 'operation, or some other fallback, depending on the operator.) It\n'
- 'should not be evaluated in a boolean context.\n'
- '\n'
- 'See Implementing the arithmetic operations for more details.\n'
- '\n'
- 'Changed in version 3.9: Evaluating "NotImplemented" in a boolean\n'
- 'context is deprecated. While it currently evaluates as true, it '
- 'will\n'
- 'emit a "DeprecationWarning". It will raise a "TypeError" in a '
- 'future\n'
- 'version of Python.\n'
- '\n'
- '\n'
- 'Ellipsis\n'
- '========\n'
- '\n'
- 'This type has a single value. There is a single object with this\n'
- 'value. This object is accessed through the literal "..." or the '
- 'built-\n'
- 'in name "Ellipsis". Its truth value is true.\n'
- '\n'
- '\n'
- '"numbers.Number"\n'
- '================\n'
- '\n'
- 'These are created by numeric literals and returned as results by\n'
- 'arithmetic operators and arithmetic built-in functions. Numeric\n'
- 'objects are immutable; once created their value never changes. '
- 'Python\n'
- 'numbers are of course strongly related to mathematical numbers, '
- 'but\n'
- 'subject to the limitations of numerical representation in '
- 'computers.\n'
- '\n'
- 'The string representations of the numeric classes, computed by\n'
- '"__repr__()" and "__str__()", have the following properties:\n'
- '\n'
- '* They are valid numeric literals which, when passed to their '
- 'class\n'
- ' constructor, produce an object having the value of the original\n'
- ' numeric.\n'
- '\n'
- '* The representation is in base 10, when possible.\n'
- '\n'
- '* Leading zeros, possibly excepting a single zero before a decimal\n'
- ' point, are not shown.\n'
- '\n'
- '* Trailing zeros, possibly excepting a single zero after a decimal\n'
- ' point, are not shown.\n'
- '\n'
- '* A sign is shown only when the number is negative.\n'
- '\n'
- 'Python distinguishes between integers, floating-point numbers, and\n'
- 'complex numbers:\n'
- '\n'
- '\n'
- '"numbers.Integral"\n'
- '------------------\n'
- '\n'
- 'These represent elements from the mathematical set of integers\n'
- '(positive and negative).\n'
- '\n'
- 'Note:\n'
- '\n'
- ' The rules for integer representation are intended to give the '
- 'most\n'
- ' meaningful interpretation of shift and mask operations involving\n'
- ' negative integers.\n'
- '\n'
- 'There are two types of integers:\n'
- '\n'
- 'Integers ("int")\n'
- ' These represent numbers in an unlimited range, subject to '
- 'available\n'
- ' (virtual) memory only. For the purpose of shift and mask\n'
- ' operations, a binary representation is assumed, and negative\n'
- ' numbers are represented in a variant of 2’s complement which '
- 'gives\n'
- ' the illusion of an infinite string of sign bits extending to '
- 'the\n'
- ' left.\n'
- '\n'
- 'Booleans ("bool")\n'
- ' These represent the truth values False and True. The two '
- 'objects\n'
- ' representing the values "False" and "True" are the only Boolean\n'
- ' objects. The Boolean type is a subtype of the integer type, and\n'
- ' Boolean values behave like the values 0 and 1, respectively, in\n'
- ' almost all contexts, the exception being that when converted to '
- 'a\n'
- ' string, the strings ""False"" or ""True"" are returned,\n'
- ' respectively.\n'
- '\n'
- '\n'
- '"numbers.Real" ("float")\n'
- '------------------------\n'
- '\n'
- 'These represent machine-level double precision floating-point '
- 'numbers.\n'
- 'You are at the mercy of the underlying machine architecture (and C '
- 'or\n'
- 'Java implementation) for the accepted range and handling of '
- 'overflow.\n'
- 'Python does not support single-precision floating-point numbers; '
- 'the\n'
- 'savings in processor and memory usage that are usually the reason '
- 'for\n'
- 'using these are dwarfed by the overhead of using objects in Python, '
- 'so\n'
- 'there is no reason to complicate the language with two kinds of\n'
- 'floating-point numbers.\n'
- '\n'
- '\n'
- '"numbers.Complex" ("complex")\n'
- '-----------------------------\n'
- '\n'
- 'These represent complex numbers as a pair of machine-level double\n'
- 'precision floating-point numbers. The same caveats apply as for\n'
- 'floating-point numbers. The real and imaginary parts of a complex\n'
- 'number "z" can be retrieved through the read-only attributes '
- '"z.real"\n'
- 'and "z.imag".\n'
- '\n'
- '\n'
- 'Sequences\n'
- '=========\n'
- '\n'
- 'These represent finite ordered sets indexed by non-negative '
- 'numbers.\n'
- 'The built-in function "len()" returns the number of items of a\n'
- 'sequence. When the length of a sequence is *n*, the index set '
- 'contains\n'
- 'the numbers 0, 1, …, *n*-1. Item *i* of sequence *a* is selected '
- 'by\n'
- '"a[i]". Some sequences, including built-in sequences, interpret\n'
- 'negative subscripts by adding the sequence length. For example,\n'
- '"a[-2]" equals "a[n-2]", the second to last item of sequence a '
- 'with\n'
- 'length "n".\n'
- '\n'
- 'Sequences also support slicing: "a[i:j]" selects all items with '
- 'index\n'
- '*k* such that *i* "<=" *k* "<" *j*. When used as an expression, a\n'
- 'slice is a sequence of the same type. The comment above about '
- 'negative\n'
- 'indexes also applies to negative slice positions.\n'
- '\n'
- 'Some sequences also support “extended slicing” with a third “step”\n'
- 'parameter: "a[i:j:k]" selects all items of *a* with index *x* where '
- '"x\n'
- '= i + n*k", *n* ">=" "0" and *i* "<=" *x* "<" *j*.\n'
- '\n'
- 'Sequences are distinguished according to their mutability:\n'
- '\n'
- '\n'
- 'Immutable sequences\n'
- '-------------------\n'
- '\n'
- 'An object of an immutable sequence type cannot change once it is\n'
- 'created. (If the object contains references to other objects, '
- 'these\n'
- 'other objects may be mutable and may be changed; however, the\n'
- 'collection of objects directly referenced by an immutable object\n'
- 'cannot change.)\n'
- '\n'
- 'The following types are immutable sequences:\n'
- '\n'
- 'Strings\n'
- ' A string is a sequence of values that represent Unicode code\n'
- ' points. All the code points in the range "U+0000 - U+10FFFF" can '
- 'be\n'
- ' represented in a string. Python doesn’t have a char type; '
- 'instead,\n'
- ' every code point in the string is represented as a string '
- 'object\n'
- ' with length "1". The built-in function "ord()" converts a code\n'
- ' point from its string form to an integer in the range "0 - '
- '10FFFF";\n'
- ' "chr()" converts an integer in the range "0 - 10FFFF" to the\n'
- ' corresponding length "1" string object. "str.encode()" can be '
- 'used\n'
- ' to convert a "str" to "bytes" using the given text encoding, '
- 'and\n'
- ' "bytes.decode()" can be used to achieve the opposite.\n'
- '\n'
- 'Tuples\n'
- ' The items of a tuple are arbitrary Python objects. Tuples of two '
- 'or\n'
- ' more items are formed by comma-separated lists of expressions. '
- 'A\n'
- ' tuple of one item (a ‘singleton’) can be formed by affixing a '
- 'comma\n'
- ' to an expression (an expression by itself does not create a '
- 'tuple,\n'
- ' since parentheses must be usable for grouping of expressions). '
- 'An\n'
- ' empty tuple can be formed by an empty pair of parentheses.\n'
- '\n'
- 'Bytes\n'
- ' A bytes object is an immutable array. The items are 8-bit '
- 'bytes,\n'
- ' represented by integers in the range 0 <= x < 256. Bytes '
- 'literals\n'
- ' (like "b\'abc\'") and the built-in "bytes()" constructor can be '
- 'used\n'
- ' to create bytes objects. Also, bytes objects can be decoded to\n'
- ' strings via the "decode()" method.\n'
- '\n'
- '\n'
- 'Mutable sequences\n'
- '-----------------\n'
- '\n'
- 'Mutable sequences can be changed after they are created. The\n'
- 'subscription and slicing notations can be used as the target of\n'
- 'assignment and "del" (delete) statements.\n'
- '\n'
- 'Note:\n'
- '\n'
- ' The "collections" and "array" module provide additional examples '
- 'of\n'
- ' mutable sequence types.\n'
- '\n'
- 'There are currently two intrinsic mutable sequence types:\n'
- '\n'
- 'Lists\n'
- ' The items of a list are arbitrary Python objects. Lists are '
- 'formed\n'
- ' by placing a comma-separated list of expressions in square\n'
- ' brackets. (Note that there are no special cases needed to form\n'
- ' lists of length 0 or 1.)\n'
- '\n'
- 'Byte Arrays\n'
- ' A bytearray object is a mutable array. They are created by the\n'
- ' built-in "bytearray()" constructor. Aside from being mutable '
- '(and\n'
- ' hence unhashable), byte arrays otherwise provide the same '
- 'interface\n'
- ' and functionality as immutable "bytes" objects.\n'
- '\n'
- '\n'
- 'Set types\n'
- '=========\n'
- '\n'
- 'These represent unordered, finite sets of unique, immutable '
- 'objects.\n'
- 'As such, they cannot be indexed by any subscript. However, they can '
- 'be\n'
- 'iterated over, and the built-in function "len()" returns the number '
- 'of\n'
- 'items in a set. Common uses for sets are fast membership testing,\n'
- 'removing duplicates from a sequence, and computing mathematical\n'
- 'operations such as intersection, union, difference, and symmetric\n'
- 'difference.\n'
- '\n'
- 'For set elements, the same immutability rules apply as for '
- 'dictionary\n'
- 'keys. Note that numeric types obey the normal rules for numeric\n'
- 'comparison: if two numbers compare equal (e.g., "1" and "1.0"), '
- 'only\n'
- 'one of them can be contained in a set.\n'
- '\n'
- 'There are currently two intrinsic set types:\n'
- '\n'
- 'Sets\n'
- ' These represent a mutable set. They are created by the built-in\n'
- ' "set()" constructor and can be modified afterwards by several\n'
- ' methods, such as "add()".\n'
- '\n'
- 'Frozen sets\n'
- ' These represent an immutable set. They are created by the '
- 'built-in\n'
- ' "frozenset()" constructor. As a frozenset is immutable and\n'
- ' *hashable*, it can be used again as an element of another set, '
- 'or\n'
- ' as a dictionary key.\n'
- '\n'
- '\n'
- 'Mappings\n'
- '========\n'
- '\n'
- 'These represent finite sets of objects indexed by arbitrary index\n'
- 'sets. The subscript notation "a[k]" selects the item indexed by '
- '"k"\n'
- 'from the mapping "a"; this can be used in expressions and as the\n'
- 'target of assignments or "del" statements. The built-in function\n'
- '"len()" returns the number of items in a mapping.\n'
- '\n'
- 'There is currently a single intrinsic mapping type:\n'
- '\n'
- '\n'
- 'Dictionaries\n'
- '------------\n'
- '\n'
- 'These represent finite sets of objects indexed by nearly arbitrary\n'
- 'values. The only types of values not acceptable as keys are '
- 'values\n'
- 'containing lists or dictionaries or other mutable types that are\n'
- 'compared by value rather than by object identity, the reason being\n'
- 'that the efficient implementation of dictionaries requires a key’s\n'
- 'hash value to remain constant. Numeric types used for keys obey '
- 'the\n'
- 'normal rules for numeric comparison: if two numbers compare equal\n'
- '(e.g., "1" and "1.0") then they can be used interchangeably to '
- 'index\n'
- 'the same dictionary entry.\n'
- '\n'
- 'Dictionaries preserve insertion order, meaning that keys will be\n'
- 'produced in the same order they were added sequentially over the\n'
- 'dictionary. Replacing an existing key does not change the order,\n'
- 'however removing a key and re-inserting it will add it to the end\n'
- 'instead of keeping its old place.\n'
- '\n'
- 'Dictionaries are mutable; they can be created by the "{}" notation\n'
- '(see section Dictionary displays).\n'
- '\n'
- 'The extension modules "dbm.ndbm" and "dbm.gnu" provide additional\n'
- 'examples of mapping types, as does the "collections" module.\n'
- '\n'
- 'Changed in version 3.7: Dictionaries did not preserve insertion '
- 'order\n'
- 'in versions of Python before 3.6. In CPython 3.6, insertion order '
- 'was\n'
- 'preserved, but it was considered an implementation detail at that '
- 'time\n'
- 'rather than a language guarantee.\n'
- '\n'
- '\n'
- 'Callable types\n'
- '==============\n'
- '\n'
- 'These are the types to which the function call operation (see '
- 'section\n'
- 'Calls) can be applied:\n'
- '\n'
- '\n'
- 'User-defined functions\n'
- '----------------------\n'
- '\n'
- 'A user-defined function object is created by a function definition\n'
- '(see section Function definitions). It should be called with an\n'
- 'argument list containing the same number of items as the '
- 'function’s\n'
- 'formal parameter list.\n'
- '\n'
- '\n'
- 'Special read-only attributes\n'
- '~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n'
- '\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| Attribute | '
- 'Meaning |\n'
- '|====================================================|====================================================|\n'
- '| function.__globals__ | A reference '
- 'to the "dictionary" that holds the |\n'
- '| | function’s '
- 'global variables – the global namespace |\n'
- '| | of the '
- 'module in which the function was defined. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| function.__closure__ | "None" or a '
- '"tuple" of cells that contain bindings |\n'
- '| | for the '
- 'function’s free variables. A cell object |\n'
- '| | has the '
- 'attribute "cell_contents". This can be |\n'
- '| | used to get '
- 'the value of the cell, as well as set |\n'
- '| | the '
- 'value. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '\n'
- '\n'
- 'Special writable attributes\n'
- '~~~~~~~~~~~~~~~~~~~~~~~~~~~\n'
- '\n'
- 'Most of these attributes check the type of the assigned value:\n'
- '\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| Attribute | '
- 'Meaning |\n'
- '|====================================================|====================================================|\n'
- '| function.__doc__ | The '
- 'function’s documentation string, or "None" if |\n'
- '| | '
- 'unavailable. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| function.__name__ | The '
- 'function’s name. See also: "__name__ |\n'
- '| | '
- 'attributes". |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| function.__qualname__ | The '
- 'function’s *qualified name*. See also: |\n'
- '| | '
- '"__qualname__ attributes". Added in version 3.3. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| function.__module__ | The name of '
- 'the module the function was defined |\n'
- '| | in, or '
- '"None" if unavailable. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| function.__defaults__ | A "tuple" '
- 'containing default *parameter* values |\n'
- '| | for those '
- 'parameters that have defaults, or "None" |\n'
- '| | if no '
- 'parameters have a default value. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| function.__code__ | The code '
- 'object representing the compiled function |\n'
- '| | '
- 'body. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| function.__dict__ | The '
- 'namespace supporting arbitrary function |\n'
- '| | attributes. '
- 'See also: "__dict__ attributes". |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| function.__annotations__ | A '
- '"dictionary" containing annotations of |\n'
- '| | '
- '*parameters*. The keys of the dictionary are the |\n'
- '| | parameter '
- 'names, and "\'return\'" for the return |\n'
- '| | annotation, '
- 'if provided. See also: Annotations |\n'
- '| | Best '
- 'Practices. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| function.__kwdefaults__ | A '
- '"dictionary" containing defaults for keyword- |\n'
- '| | only '
- '*parameters*. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| function.__type_params__ | A "tuple" '
- 'containing the type parameters of a |\n'
- '| | generic '
- 'function. Added in version 3.12. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '\n'
- 'Function objects also support getting and setting arbitrary\n'
- 'attributes, which can be used, for example, to attach metadata to\n'
- 'functions. Regular attribute dot-notation is used to get and set '
- 'such\n'
- 'attributes.\n'
- '\n'
- '**CPython implementation detail:** CPython’s current '
- 'implementation\n'
- 'only supports function attributes on user-defined functions. '
- 'Function\n'
- 'attributes on built-in functions may be supported in the future.\n'
- '\n'
- 'Additional information about a function’s definition can be '
- 'retrieved\n'
- 'from its code object (accessible via the "__code__" attribute).\n'
- '\n'
- '\n'
- 'Instance methods\n'
- '----------------\n'
- '\n'
- 'An instance method object combines a class, a class instance and '
- 'any\n'
- 'callable object (normally a user-defined function).\n'
- '\n'
- 'Special read-only attributes:\n'
- '\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| method.__self__ | Refers to '
- 'the class instance object to which the |\n'
- '| | method is '
- 'bound |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| method.__func__ | Refers to '
- 'the original function object |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| method.__doc__ | The method’s '
- 'documentation (same as |\n'
- '| | '
- '"method.__func__.__doc__"). A "string" if the |\n'
- '| | original '
- 'function had a docstring, else "None". |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| method.__name__ | The name of '
- 'the method (same as |\n'
- '| | '
- '"method.__func__.__name__") |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| method.__module__ | The name of '
- 'the module the method was defined in, |\n'
- '| | or "None" if '
- 'unavailable. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '\n'
- 'Methods also support accessing (but not setting) the arbitrary\n'
- 'function attributes on the underlying function object.\n'
- '\n'
- 'User-defined method objects may be created when getting an '
- 'attribute\n'
- 'of a class (perhaps via an instance of that class), if that '
- 'attribute\n'
- 'is a user-defined function object or a "classmethod" object.\n'
- '\n'
- 'When an instance method object is created by retrieving a '
- 'user-defined\n'
- 'function object from a class via one of its instances, its '
- '"__self__"\n'
- 'attribute is the instance, and the method object is said to be\n'
- '*bound*. The new method’s "__func__" attribute is the original\n'
- 'function object.\n'
- '\n'
- 'When an instance method object is created by retrieving a\n'
- '"classmethod" object from a class or instance, its "__self__"\n'
- 'attribute is the class itself, and its "__func__" attribute is the\n'
- 'function object underlying the class method.\n'
- '\n'
- 'When an instance method object is called, the underlying function\n'
- '("__func__") is called, inserting the class instance ("__self__") '
- 'in\n'
- 'front of the argument list. For instance, when "C" is a class '
- 'which\n'
- 'contains a definition for a function "f()", and "x" is an instance '
- 'of\n'
- '"C", calling "x.f(1)" is equivalent to calling "C.f(x, 1)".\n'
- '\n'
- 'When an instance method object is derived from a "classmethod" '
- 'object,\n'
- 'the “class instance” stored in "__self__" will actually be the '
- 'class\n'
- 'itself, so that calling either "x.f(1)" or "C.f(1)" is equivalent '
- 'to\n'
- 'calling "f(C,1)" where "f" is the underlying function.\n'
- '\n'
- 'It is important to note that user-defined functions which are\n'
- 'attributes of a class instance are not converted to bound methods;\n'
- 'this *only* happens when the function is an attribute of the '
- 'class.\n'
- '\n'
- '\n'
- 'Generator functions\n'
- '-------------------\n'
- '\n'
- 'A function or method which uses the "yield" statement (see section '
- 'The\n'
- 'yield statement) is called a *generator function*. Such a '
- 'function,\n'
- 'when called, always returns an *iterator* object which can be used '
- 'to\n'
- 'execute the body of the function: calling the iterator’s\n'
- '"iterator.__next__()" method will cause the function to execute '
- 'until\n'
- 'it provides a value using the "yield" statement. When the '
- 'function\n'
- 'executes a "return" statement or falls off the end, a '
- '"StopIteration"\n'
- 'exception is raised and the iterator will have reached the end of '
- 'the\n'
- 'set of values to be returned.\n'
- '\n'
- '\n'
- 'Coroutine functions\n'
- '-------------------\n'
- '\n'
- 'A function or method which is defined using "async def" is called '
- 'a\n'
- '*coroutine function*. Such a function, when called, returns a\n'
- '*coroutine* object. It may contain "await" expressions, as well '
- 'as\n'
- '"async with" and "async for" statements. See also the Coroutine\n'
- 'Objects section.\n'
- '\n'
- '\n'
- 'Asynchronous generator functions\n'
- '--------------------------------\n'
- '\n'
- 'A function or method which is defined using "async def" and which '
- 'uses\n'
- 'the "yield" statement is called a *asynchronous generator '
- 'function*.\n'
- 'Such a function, when called, returns an *asynchronous iterator*\n'
- 'object which can be used in an "async for" statement to execute '
- 'the\n'
- 'body of the function.\n'
- '\n'
- 'Calling the asynchronous iterator’s "aiterator.__anext__" method '
- 'will\n'
- 'return an *awaitable* which when awaited will execute until it\n'
- 'provides a value using the "yield" expression. When the function\n'
- 'executes an empty "return" statement or falls off the end, a\n'
- '"StopAsyncIteration" exception is raised and the asynchronous '
- 'iterator\n'
- 'will have reached the end of the set of values to be yielded.\n'
- '\n'
- '\n'
- 'Built-in functions\n'
- '------------------\n'
- '\n'
- 'A built-in function object is a wrapper around a C function. '
- 'Examples\n'
- 'of built-in functions are "len()" and "math.sin()" ("math" is a\n'
- 'standard built-in module). The number and type of the arguments '
- 'are\n'
- 'determined by the C function. Special read-only attributes:\n'
- '\n'
- '* "__doc__" is the function’s documentation string, or "None" if\n'
- ' unavailable. See "function.__doc__".\n'
- '\n'
- '* "__name__" is the function’s name. See "function.__name__".\n'
- '\n'
- '* "__self__" is set to "None" (but see the next item).\n'
- '\n'
- '* "__module__" is the name of the module the function was defined '
- 'in\n'
- ' or "None" if unavailable. See "function.__module__".\n'
- '\n'
- '\n'
- 'Built-in methods\n'
- '----------------\n'
- '\n'
- 'This is really a different disguise of a built-in function, this '
- 'time\n'
- 'containing an object passed to the C function as an implicit extra\n'
- 'argument. An example of a built-in method is "alist.append()",\n'
- 'assuming *alist* is a list object. In this case, the special '
- 'read-only\n'
- 'attribute "__self__" is set to the object denoted by *alist*. (The\n'
- 'attribute has the same semantics as it does with "other instance\n'
- 'methods".)\n'
- '\n'
- '\n'
- 'Classes\n'
- '-------\n'
- '\n'
- 'Classes are callable. These objects normally act as factories for '
- 'new\n'
- 'instances of themselves, but variations are possible for class '
- 'types\n'
- 'that override "__new__()". The arguments of the call are passed '
- 'to\n'
- '"__new__()" and, in the typical case, to "__init__()" to '
- 'initialize\n'
- 'the new instance.\n'
- '\n'
- '\n'
- 'Class Instances\n'
- '---------------\n'
- '\n'
- 'Instances of arbitrary classes can be made callable by defining a\n'
- '"__call__()" method in their class.\n'
- '\n'
- '\n'
- 'Modules\n'
- '=======\n'
- '\n'
- 'Modules are a basic organizational unit of Python code, and are\n'
- 'created by the import system as invoked either by the "import"\n'
- 'statement, or by calling functions such as '
- '"importlib.import_module()"\n'
- 'and built-in "__import__()". A module object has a namespace\n'
- 'implemented by a "dictionary" object (this is the dictionary\n'
- 'referenced by the "__globals__" attribute of functions defined in '
- 'the\n'
- 'module). Attribute references are translated to lookups in this\n'
- 'dictionary, e.g., "m.x" is equivalent to "m.__dict__["x"]". A '
- 'module\n'
- 'object does not contain the code object used to initialize the '
- 'module\n'
- '(since it isn’t needed once the initialization is done).\n'
- '\n'
- 'Attribute assignment updates the module’s namespace dictionary, '
- 'e.g.,\n'
- '"m.x = 1" is equivalent to "m.__dict__["x"] = 1".\n'
- '\n'
- '\n'
- 'Import-related attributes on module objects\n'
- '-------------------------------------------\n'
- '\n'
- 'Module objects have the following attributes that relate to the '
- 'import\n'
- 'system. When a module is created using the machinery associated '
- 'with\n'
- 'the import system, these attributes are filled in based on the\n'
- 'module’s *spec*, before the *loader* executes and loads the '
- 'module.\n'
- '\n'
- 'To create a module dynamically rather than using the import '
- 'system,\n'
- 'it’s recommended to use "importlib.util.module_from_spec()", which\n'
- 'will set the various import-controlled attributes to appropriate\n'
- 'values. It’s also possible to use the "types.ModuleType" '
- 'constructor\n'
- 'to create modules directly, but this technique is more error-prone, '
- 'as\n'
- 'most attributes must be manually set on the module object after it '
- 'has\n'
- 'been created when using this approach.\n'
- '\n'
- 'Caution:\n'
- '\n'
- ' With the exception of "__name__", it is **strongly** recommended\n'
- ' that you rely on "__spec__" and its attributes instead of any of '
- 'the\n'
- ' other individual attributes listed in this subsection. Note that\n'
- ' updating an attribute on "__spec__" will not update the\n'
- ' corresponding attribute on the module itself:\n'
- '\n'
- ' >>> import typing\n'
- ' >>> typing.__name__, typing.__spec__.name\n'
- " ('typing', 'typing')\n"
- " >>> typing.__spec__.name = 'spelling'\n"
- ' >>> typing.__name__, typing.__spec__.name\n'
- " ('typing', 'spelling')\n"
- " >>> typing.__name__ = 'keyboard_smashing'\n"
- ' >>> typing.__name__, typing.__spec__.name\n'
- " ('keyboard_smashing', 'spelling')\n"
- '\n'
- 'module.__name__\n'
- '\n'
- ' The name used to uniquely identify the module in the import '
- 'system.\n'
- ' For a directly executed module, this will be set to '
- '""__main__"".\n'
- '\n'
- ' This attribute must be set to the fully qualified name of the\n'
- ' module. It is expected to match the value of\n'
- ' "module.__spec__.name".\n'
- '\n'
- 'module.__spec__\n'
- '\n'
- ' A record of the module’s import-system-related state.\n'
- '\n'
- ' Set to the "module spec" that was used when importing the '
- 'module.\n'
- ' See Module specs for more details.\n'
- '\n'
- ' Added in version 3.4.\n'
- '\n'
- 'module.__package__\n'
- '\n'
- ' The *package* a module belongs to.\n'
- '\n'
- ' If the module is top-level (that is, not a part of any specific\n'
- ' package) then the attribute should be set to "\'\'" (the empty\n'
- ' string). Otherwise, it should be set to the name of the '
- 'module’s\n'
- ' package (which can be equal to "module.__name__" if the module\n'
- ' itself is a package). See **PEP 366** for further details.\n'
- '\n'
- ' This attribute is used instead of "__name__" to calculate '
- 'explicit\n'
- ' relative imports for main modules. It defaults to "None" for\n'
- ' modules created dynamically using the "types.ModuleType"\n'
- ' constructor; use "importlib.util.module_from_spec()" instead to\n'
- ' ensure the attribute is set to a "str".\n'
- '\n'
- ' It is **strongly** recommended that you use\n'
- ' "module.__spec__.parent" instead of "module.__package__".\n'
- ' "__package__" is now only used as a fallback if '
- '"__spec__.parent"\n'
- ' is not set, and this fallback path is deprecated.\n'
- '\n'
- ' Changed in version 3.4: This attribute now defaults to "None" '
- 'for\n'
- ' modules created dynamically using the "types.ModuleType"\n'
- ' constructor. Previously the attribute was optional.\n'
- '\n'
- ' Changed in version 3.6: The value of "__package__" is expected '
- 'to\n'
- ' be the same as "__spec__.parent". "__package__" is now only used '
- 'as\n'
- ' a fallback during import resolution if "__spec__.parent" is not\n'
- ' defined.\n'
- '\n'
- ' Changed in version 3.10: "ImportWarning" is raised if an import\n'
- ' resolution falls back to "__package__" instead of\n'
- ' "__spec__.parent".\n'
- '\n'
- ' Changed in version 3.12: Raise "DeprecationWarning" instead of\n'
- ' "ImportWarning" when falling back to "__package__" during '
- 'import\n'
- ' resolution.\n'
- '\n'
- 'module.__loader__\n'
- '\n'
- ' The *loader* object that the import machinery used to load the\n'
- ' module.\n'
- '\n'
- ' This attribute is mostly useful for introspection, but can be '
- 'used\n'
- ' for additional loader-specific functionality, for example '
- 'getting\n'
- ' data associated with a loader.\n'
- '\n'
- ' "__loader__" defaults to "None" for modules created dynamically\n'
- ' using the "types.ModuleType" constructor; use\n'
- ' "importlib.util.module_from_spec()" instead to ensure the '
- 'attribute\n'
- ' is set to a *loader* object.\n'
- '\n'
- ' It is **strongly** recommended that you use\n'
- ' "module.__spec__.loader" instead of "module.__loader__".\n'
- '\n'
- ' Changed in version 3.4: This attribute now defaults to "None" '
- 'for\n'
- ' modules created dynamically using the "types.ModuleType"\n'
- ' constructor. Previously the attribute was optional.\n'
- '\n'
- ' Deprecated since version 3.12, will be removed in version 3.16:\n'
- ' Setting "__loader__" on a module while failing to set\n'
- ' "__spec__.loader" is deprecated. In Python 3.16, "__loader__" '
- 'will\n'
- ' cease to be set or taken into consideration by the import system '
- 'or\n'
- ' the standard library.\n'
- '\n'
- 'module.__path__\n'
- '\n'
- ' A (possibly empty) *sequence* of strings enumerating the '
- 'locations\n'
- ' where the package’s submodules will be found. Non-package '
- 'modules\n'
- ' should not have a "__path__" attribute. See __path__ attributes '
- 'on\n'
- ' modules for more details.\n'
- '\n'
- ' It is **strongly** recommended that you use\n'
- ' "module.__spec__.submodule_search_locations" instead of\n'
- ' "module.__path__".\n'
- '\n'
- 'module.__file__\n'
- '\n'
- 'module.__cached__\n'
- '\n'
- ' "__file__" and "__cached__" are both optional attributes that '
- 'may\n'
- ' or may not be set. Both attributes should be a "str" when they '
- 'are\n'
- ' available.\n'
- '\n'
- ' "__file__" indicates the pathname of the file from which the '
- 'module\n'
- ' was loaded (if loaded from a file), or the pathname of the '
- 'shared\n'
- ' library file for extension modules loaded dynamically from a '
- 'shared\n'
- ' library. It might be missing for certain types of modules, such '
- 'as\n'
- ' C modules that are statically linked into the interpreter, and '
- 'the\n'
- ' import system may opt to leave it unset if it has no semantic\n'
- ' meaning (for example, a module loaded from a database).\n'
- '\n'
- ' If "__file__" is set then the "__cached__" attribute might also '
- 'be\n'
- ' set, which is the path to any compiled version of the code '
- '(for\n'
- ' example, a byte-compiled file). The file does not need to exist '
- 'to\n'
- ' set this attribute; the path can simply point to where the '
- 'compiled\n'
- ' file *would* exist (see **PEP 3147**).\n'
- '\n'
- ' Note that "__cached__" may be set even if "__file__" is not '
- 'set.\n'
- ' However, that scenario is quite atypical. Ultimately, the '
- '*loader*\n'
- ' is what makes use of the module spec provided by the *finder* '
- '(from\n'
- ' which "__file__" and "__cached__" are derived). So if a loader '
- 'can\n'
- ' load from a cached module but otherwise does not load from a '
- 'file,\n'
- ' that atypical scenario may be appropriate.\n'
- '\n'
- ' It is **strongly** recommended that you use\n'
- ' "module.__spec__.cached" instead of "module.__cached__".\n'
- '\n'
- '\n'
- 'Other writable attributes on module objects\n'
- '-------------------------------------------\n'
- '\n'
- 'As well as the import-related attributes listed above, module '
- 'objects\n'
- 'also have the following writable attributes:\n'
- '\n'
- 'module.__doc__\n'
- '\n'
- ' The module’s documentation string, or "None" if unavailable. '
- 'See\n'
- ' also: "__doc__ attributes".\n'
- '\n'
- 'module.__annotations__\n'
- '\n'
- ' A dictionary containing *variable annotations* collected during\n'
- ' module body execution. For best practices on working with\n'
- ' "__annotations__", please see Annotations Best Practices.\n'
- '\n'
- '\n'
- 'Module dictionaries\n'
- '-------------------\n'
- '\n'
- 'Module objects also have the following special read-only '
- 'attribute:\n'
- '\n'
- 'module.__dict__\n'
- '\n'
- ' The module’s namespace as a dictionary object. Uniquely among '
- 'the\n'
- ' attributes listed here, "__dict__" cannot be accessed as a '
- 'global\n'
- ' variable from within a module; it can only be accessed as an\n'
- ' attribute on module objects.\n'
- '\n'
- ' **CPython implementation detail:** Because of the way CPython\n'
- ' clears module dictionaries, the module dictionary will be '
- 'cleared\n'
- ' when the module falls out of scope even if the dictionary still '
- 'has\n'
- ' live references. To avoid this, copy the dictionary or keep '
- 'the\n'
- ' module around while using its dictionary directly.\n'
- '\n'
- '\n'
- 'Custom classes\n'
- '==============\n'
- '\n'
- 'Custom class types are typically created by class definitions (see\n'
- 'section Class definitions). A class has a namespace implemented by '
- 'a\n'
- 'dictionary object. Class attribute references are translated to\n'
- 'lookups in this dictionary, e.g., "C.x" is translated to\n'
- '"C.__dict__["x"]" (although there are a number of hooks which '
- 'allow\n'
- 'for other means of locating attributes). When the attribute name '
- 'is\n'
- 'not found there, the attribute search continues in the base '
- 'classes.\n'
- 'This search of the base classes uses the C3 method resolution '
- 'order\n'
- 'which behaves correctly even in the presence of ‘diamond’ '
- 'inheritance\n'
- 'structures where there are multiple inheritance paths leading back '
- 'to\n'
- 'a common ancestor. Additional details on the C3 MRO used by Python '
- 'can\n'
- 'be found at The Python 2.3 Method Resolution Order.\n'
- '\n'
- 'When a class attribute reference (for class "C", say) would yield '
- 'a\n'
- 'class method object, it is transformed into an instance method '
- 'object\n'
- 'whose "__self__" attribute is "C". When it would yield a\n'
- '"staticmethod" object, it is transformed into the object wrapped '
- 'by\n'
- 'the static method object. See section Implementing Descriptors for\n'
- 'another way in which attributes retrieved from a class may differ '
- 'from\n'
- 'those actually contained in its "__dict__".\n'
- '\n'
- 'Class attribute assignments update the class’s dictionary, never '
- 'the\n'
- 'dictionary of a base class.\n'
- '\n'
- 'A class object can be called (see above) to yield a class instance\n'
- '(see below).\n'
- '\n'
- '\n'
- 'Special attributes\n'
- '------------------\n'
- '\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| Attribute | '
- 'Meaning |\n'
- '|====================================================|====================================================|\n'
- '| type.__name__ | The class’s '
- 'name. See also: "__name__ attributes". |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| type.__qualname__ | The class’s '
- '*qualified name*. See also: |\n'
- '| | '
- '"__qualname__ attributes". |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| type.__module__ | The name of '
- 'the module in which the class was |\n'
- '| | '
- 'defined. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| type.__dict__ | A "mapping '
- 'proxy" providing a read-only view of |\n'
- '| | the class’s '
- 'namespace. See also: "__dict__ |\n'
- '| | '
- 'attributes". |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| type.__bases__ | A "tuple" '
- 'containing the class’s bases. In most |\n'
- '| | cases, for a '
- 'class defined as "class X(A, B, C)", |\n'
- '| | '
- '"X.__bases__" will be exactly equal to "(A, B, |\n'
- '| | '
- 'C)". |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| type.__doc__ | The class’s '
- 'documentation string, or "None" if |\n'
- '| | undefined. '
- 'Not inherited by subclasses. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| type.__annotations__ | A dictionary '
- 'containing *variable annotations* |\n'
- '| | collected '
- 'during class body execution. For best |\n'
- '| | practices on '
- 'working with "__annotations__", |\n'
- '| | please see '
- 'Annotations Best Practices. Caution: |\n'
- '| | Accessing '
- 'the "__annotations__" attribute of a |\n'
- '| | class object '
- 'directly may yield incorrect results |\n'
- '| | in the '
- 'presence of metaclasses. In addition, the |\n'
- '| | attribute '
- 'may not exist for some classes. Use |\n'
- '| | '
- '"inspect.get_annotations()" to retrieve class |\n'
- '| | annotations '
- 'safely. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| type.__type_params__ | A "tuple" '
- 'containing the type parameters of a |\n'
- '| | generic '
- 'class. Added in version 3.12. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| type.__mro__ | The "tuple" '
- 'of classes that are considered when |\n'
- '| | looking for '
- 'base classes during method resolution. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '\n'
- '\n'
- 'Special methods\n'
- '---------------\n'
- '\n'
- 'In addition to the special attributes described above, all Python\n'
- 'classes also have the following two methods available:\n'
- '\n'
- 'type.mro()\n'
- '\n'
- ' This method can be overridden by a metaclass to customize the\n'
- ' method resolution order for its instances. It is called at '
- 'class\n'
- ' instantiation, and its result is stored in "__mro__".\n'
- '\n'
- 'type.__subclasses__()\n'
- '\n'
- ' Each class keeps a list of weak references to its immediate\n'
- ' subclasses. This method returns a list of all those references\n'
- ' still alive. The list is in definition order. Example:\n'
- '\n'
- ' >>> class A: pass\n'
- ' >>> class B(A): pass\n'
- ' >>> A.__subclasses__()\n'
- " [<class 'B'>]\n"
- '\n'
- '\n'
- 'Class instances\n'
- '===============\n'
- '\n'
- 'A class instance is created by calling a class object (see above). '
- 'A\n'
- 'class instance has a namespace implemented as a dictionary which '
- 'is\n'
- 'the first place in which attribute references are searched. When '
- 'an\n'
- 'attribute is not found there, and the instance’s class has an\n'
- 'attribute by that name, the search continues with the class\n'
- 'attributes. If a class attribute is found that is a user-defined\n'
- 'function object, it is transformed into an instance method object\n'
- 'whose "__self__" attribute is the instance. Static method and '
- 'class\n'
- 'method objects are also transformed; see above under “Classes”. '
- 'See\n'
- 'section Implementing Descriptors for another way in which '
- 'attributes\n'
- 'of a class retrieved via its instances may differ from the objects\n'
- 'actually stored in the class’s "__dict__". If no class attribute '
- 'is\n'
- 'found, and the object’s class has a "__getattr__()" method, that '
- 'is\n'
- 'called to satisfy the lookup.\n'
- '\n'
- 'Attribute assignments and deletions update the instance’s '
- 'dictionary,\n'
- 'never a class’s dictionary. If the class has a "__setattr__()" or\n'
- '"__delattr__()" method, this is called instead of updating the\n'
- 'instance dictionary directly.\n'
- '\n'
- 'Class instances can pretend to be numbers, sequences, or mappings '
- 'if\n'
- 'they have methods with certain special names. See section Special\n'
- 'method names.\n'
- '\n'
- '\n'
- 'Special attributes\n'
- '------------------\n'
- '\n'
- 'object.__class__\n'
- '\n'
- ' The class to which a class instance belongs.\n'
- '\n'
- 'object.__dict__\n'
- '\n'
- ' A dictionary or other mapping object used to store an object’s\n'
- ' (writable) attributes. Not all instances have a "__dict__"\n'
- ' attribute; see the section on __slots__ for more details.\n'
- '\n'
- '\n'
- 'I/O objects (also known as file objects)\n'
- '========================================\n'
- '\n'
- 'A *file object* represents an open file. Various shortcuts are\n'
- 'available to create file objects: the "open()" built-in function, '
- 'and\n'
- 'also "os.popen()", "os.fdopen()", and the "makefile()" method of\n'
- 'socket objects (and perhaps by other functions or methods provided '
- 'by\n'
- 'extension modules).\n'
- '\n'
- 'The objects "sys.stdin", "sys.stdout" and "sys.stderr" are '
- 'initialized\n'
- 'to file objects corresponding to the interpreter’s standard input,\n'
- 'output and error streams; they are all open in text mode and '
- 'therefore\n'
- 'follow the interface defined by the "io.TextIOBase" abstract '
- 'class.\n'
- '\n'
- '\n'
- 'Internal types\n'
- '==============\n'
- '\n'
- 'A few types used internally by the interpreter are exposed to the\n'
- 'user. Their definitions may change with future versions of the\n'
- 'interpreter, but they are mentioned here for completeness.\n'
- '\n'
- '\n'
- 'Code objects\n'
- '------------\n'
- '\n'
- 'Code objects represent *byte-compiled* executable Python code, or\n'
- '*bytecode*. The difference between a code object and a function '
- 'object\n'
- 'is that the function object contains an explicit reference to the\n'
- 'function’s globals (the module in which it was defined), while a '
- 'code\n'
- 'object contains no context; also the default argument values are\n'
- 'stored in the function object, not in the code object (because '
- 'they\n'
- 'represent values calculated at run-time). Unlike function '
- 'objects,\n'
- 'code objects are immutable and contain no references (directly or\n'
- 'indirectly) to mutable objects.\n'
- '\n'
- '\n'
- 'Special read-only attributes\n'
- '~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n'
- '\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_name | The function '
- 'name |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_qualname | The fully '
- 'qualified function name Added in |\n'
- '| | version '
- '3.11. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_argcount | The total '
- 'number of positional *parameters* |\n'
- '| | (including '
- 'positional-only parameters and |\n'
- '| | parameters '
- 'with default values) that the function |\n'
- '| | '
- 'has |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_posonlyargcount | The number '
- 'of positional-only *parameters* |\n'
- '| | (including '
- 'arguments with default values) that the |\n'
- '| | function '
- 'has |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_kwonlyargcount | The number '
- 'of keyword-only *parameters* (including |\n'
- '| | arguments '
- 'with default values) that the function |\n'
- '| | '
- 'has |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_nlocals | The number '
- 'of local variables used by the function |\n'
- '| | (including '
- 'parameters) |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_varnames | A "tuple" '
- 'containing the names of the local |\n'
- '| | variables in '
- 'the function (starting with the |\n'
- '| | parameter '
- 'names) |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_cellvars | A "tuple" '
- 'containing the names of local variables |\n'
- '| | that are '
- 'referenced by nested functions inside the |\n'
- '| | '
- 'function |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_freevars | A "tuple" '
- 'containing the names of free variables |\n'
- '| | in the '
- 'function |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_code | A string '
- 'representing the sequence of *bytecode* |\n'
- '| | instructions '
- 'in the function |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_consts | A "tuple" '
- 'containing the literals used by the |\n'
- '| | *bytecode* '
- 'in the function |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_names | A "tuple" '
- 'containing the names used by the |\n'
- '| | *bytecode* '
- 'in the function |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_filename | The name of '
- 'the file from which the code was |\n'
- '| | '
- 'compiled |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_firstlineno | The line '
- 'number of the first line of the function |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_lnotab | A string '
- 'encoding the mapping from *bytecode* |\n'
- '| | offsets to '
- 'line numbers. For details, see the |\n'
- '| | source code '
- 'of the interpreter. Deprecated since |\n'
- '| | version '
- '3.12: This attribute of code objects is |\n'
- '| | deprecated, '
- 'and may be removed in Python 3.15. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_stacksize | The required '
- 'stack size of the code object |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| codeobject.co_flags | An "integer" '
- 'encoding a number of flags for the |\n'
- '| | '
- 'interpreter. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '\n'
- 'The following flag bits are defined for "co_flags": bit "0x04" is '
- 'set\n'
- 'if the function uses the "*arguments" syntax to accept an '
- 'arbitrary\n'
- 'number of positional arguments; bit "0x08" is set if the function '
- 'uses\n'
- 'the "**keywords" syntax to accept arbitrary keyword arguments; bit\n'
- '"0x20" is set if the function is a generator. See Code Objects Bit\n'
- 'Flags for details on the semantics of each flags that might be\n'
- 'present.\n'
- '\n'
- 'Future feature declarations ("from __future__ import division") '
- 'also\n'
- 'use bits in "co_flags" to indicate whether a code object was '
- 'compiled\n'
- 'with a particular feature enabled: bit "0x2000" is set if the '
- 'function\n'
- 'was compiled with future division enabled; bits "0x10" and '
- '"0x1000"\n'
- 'were used in earlier versions of Python.\n'
- '\n'
- 'Other bits in "co_flags" are reserved for internal use.\n'
- '\n'
- 'If a code object represents a function, the first item in '
- '"co_consts"\n'
- 'is the documentation string of the function, or "None" if '
- 'undefined.\n'
- '\n'
- '\n'
- 'Methods on code objects\n'
- '~~~~~~~~~~~~~~~~~~~~~~~\n'
- '\n'
- 'codeobject.co_positions()\n'
- '\n'
- ' Returns an iterable over the source code positions of each\n'
- ' *bytecode* instruction in the code object.\n'
- '\n'
- ' The iterator returns "tuple"s containing the "(start_line,\n'
- ' end_line, start_column, end_column)". The *i-th* tuple '
- 'corresponds\n'
- ' to the position of the source code that compiled to the *i-th* '
- 'code\n'
- ' unit. Column information is 0-indexed utf-8 byte offsets on the\n'
- ' given source line.\n'
- '\n'
- ' This positional information can be missing. A non-exhaustive '
- 'lists\n'
- ' of cases where this may happen:\n'
- '\n'
- ' * Running the interpreter with "-X" "no_debug_ranges".\n'
- '\n'
- ' * Loading a pyc file compiled while using "-X" '
- '"no_debug_ranges".\n'
- '\n'
- ' * Position tuples corresponding to artificial instructions.\n'
- '\n'
- ' * Line and column numbers that can’t be represented due to\n'
- ' implementation specific limitations.\n'
- '\n'
- ' When this occurs, some or all of the tuple elements can be '
- '"None".\n'
- '\n'
- ' Added in version 3.11.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' This feature requires storing column positions in code '
- 'objects\n'
- ' which may result in a small increase of disk usage of '
- 'compiled\n'
- ' Python files or interpreter memory usage. To avoid storing '
- 'the\n'
- ' extra information and/or deactivate printing the extra '
- 'traceback\n'
- ' information, the "-X" "no_debug_ranges" command line flag or '
- 'the\n'
- ' "PYTHONNODEBUGRANGES" environment variable can be used.\n'
- '\n'
- 'codeobject.co_lines()\n'
- '\n'
- ' Returns an iterator that yields information about successive '
- 'ranges\n'
- ' of *bytecode*s. Each item yielded is a "(start, end, lineno)"\n'
- ' "tuple":\n'
- '\n'
- ' * "start" (an "int") represents the offset (inclusive) of the '
- 'start\n'
- ' of the *bytecode* range\n'
- '\n'
- ' * "end" (an "int") represents the offset (exclusive) of the end '
- 'of\n'
- ' the *bytecode* range\n'
- '\n'
- ' * "lineno" is an "int" representing the line number of the\n'
- ' *bytecode* range, or "None" if the bytecodes in the given '
- 'range\n'
- ' have no line number\n'
- '\n'
- ' The items yielded will have the following properties:\n'
- '\n'
- ' * The first range yielded will have a "start" of 0.\n'
- '\n'
- ' * The "(start, end)" ranges will be non-decreasing and '
- 'consecutive.\n'
- ' That is, for any pair of "tuple"s, the "start" of the second '
- 'will\n'
- ' be equal to the "end" of the first.\n'
- '\n'
- ' * No range will be backwards: "end >= start" for all triples.\n'
- '\n'
- ' * The last "tuple" yielded will have "end" equal to the size of '
- 'the\n'
- ' *bytecode*.\n'
- '\n'
- ' Zero-width ranges, where "start == end", are allowed. '
- 'Zero-width\n'
- ' ranges are used for lines that are present in the source code, '
- 'but\n'
- ' have been eliminated by the *bytecode* compiler.\n'
- '\n'
- ' Added in version 3.10.\n'
- '\n'
- ' See also:\n'
- '\n'
- ' **PEP 626** - Precise line numbers for debugging and other '
- 'tools.\n'
- ' The PEP that introduced the "co_lines()" method.\n'
- '\n'
- 'codeobject.replace(**kwargs)\n'
- '\n'
- ' Return a copy of the code object with new values for the '
- 'specified\n'
- ' fields.\n'
- '\n'
- ' Added in version 3.8.\n'
- '\n'
- '\n'
- 'Frame objects\n'
- '-------------\n'
- '\n'
- 'Frame objects represent execution frames. They may occur in '
- 'traceback\n'
- 'objects, and are also passed to registered trace functions.\n'
- '\n'
- '\n'
- 'Special read-only attributes\n'
- '~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n'
- '\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| frame.f_back | Points to '
- 'the previous stack frame (towards the |\n'
- '| | caller), or '
- '"None" if this is the bottom stack |\n'
- '| | '
- 'frame |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| frame.f_code | The code '
- 'object being executed in this frame. |\n'
- '| | Accessing '
- 'this attribute raises an auditing event |\n'
- '| | '
- '"object.__getattr__" with arguments "obj" and |\n'
- '| | '
- '""f_code"". |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| frame.f_locals | The '
- 'dictionary used by the frame to look up local |\n'
- '| | '
- 'variables |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| frame.f_globals | The '
- 'dictionary used by the frame to look up global |\n'
- '| | '
- 'variables |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| frame.f_builtins | The '
- 'dictionary used by the frame to look up built- |\n'
- '| | in '
- '(intrinsic) names |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| frame.f_lasti | The “precise '
- 'instruction” of the frame object |\n'
- '| | (this is an '
- 'index into the *bytecode* string of |\n'
- '| | the code '
- 'object) |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '\n'
- '\n'
- 'Special writable attributes\n'
- '~~~~~~~~~~~~~~~~~~~~~~~~~~~\n'
- '\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| frame.f_trace | If not '
- '"None", this is a function called for |\n'
- '| | various '
- 'events during code execution (this is used |\n'
- '| | by '
- 'debuggers). Normally an event is triggered for |\n'
- '| | each new '
- 'source line (see "f_trace_lines"). |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| frame.f_trace_lines | Set this '
- 'attribute to "False" to disable |\n'
- '| | triggering a '
- 'tracing event for each source line. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| frame.f_trace_opcodes | Set this '
- 'attribute to "True" to allow per-opcode |\n'
- '| | events to be '
- 'requested. Note that this may lead to |\n'
- '| | undefined '
- 'interpreter behaviour if exceptions |\n'
- '| | raised by '
- 'the trace function escape to the |\n'
- '| | function '
- 'being traced. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| frame.f_lineno | The current '
- 'line number of the frame – writing to |\n'
- '| | this from '
- 'within a trace function jumps to the |\n'
- '| | given line '
- '(only for the bottom-most frame). A |\n'
- '| | debugger can '
- 'implement a Jump command (aka Set |\n'
- '| | Next '
- 'Statement) by writing to this attribute. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '\n'
- '\n'
- 'Frame object methods\n'
- '~~~~~~~~~~~~~~~~~~~~\n'
- '\n'
- 'Frame objects support one method:\n'
- '\n'
- 'frame.clear()\n'
- '\n'
- ' This method clears all references to local variables held by '
- 'the\n'
- ' frame. Also, if the frame belonged to a *generator*, the '
- 'generator\n'
- ' is finalized. This helps break reference cycles involving '
- 'frame\n'
- ' objects (for example when catching an exception and storing its\n'
- ' traceback for later use).\n'
- '\n'
- ' "RuntimeError" is raised if the frame is currently executing.\n'
- '\n'
- ' Added in version 3.4.\n'
- '\n'
- '\n'
- 'Traceback objects\n'
- '-----------------\n'
- '\n'
- 'Traceback objects represent the stack trace of an exception. A\n'
- 'traceback object is implicitly created when an exception occurs, '
- 'and\n'
- 'may also be explicitly created by calling "types.TracebackType".\n'
- '\n'
- 'Changed in version 3.7: Traceback objects can now be explicitly\n'
- 'instantiated from Python code.\n'
- '\n'
- 'For implicitly created tracebacks, when the search for an '
- 'exception\n'
- 'handler unwinds the execution stack, at each unwound level a '
- 'traceback\n'
- 'object is inserted in front of the current traceback. When an\n'
- 'exception handler is entered, the stack trace is made available to '
- 'the\n'
- 'program. (See section The try statement.) It is accessible as the\n'
- 'third item of the tuple returned by "sys.exc_info()", and as the\n'
- '"__traceback__" attribute of the caught exception.\n'
- '\n'
- 'When the program contains no suitable handler, the stack trace is\n'
- 'written (nicely formatted) to the standard error stream; if the\n'
- 'interpreter is interactive, it is also made available to the user '
- 'as\n'
- '"sys.last_traceback".\n'
- '\n'
- 'For explicitly created tracebacks, it is up to the creator of the\n'
- 'traceback to determine how the "tb_next" attributes should be '
- 'linked\n'
- 'to form a full stack trace.\n'
- '\n'
- 'Special read-only attributes:\n'
- '\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| traceback.tb_frame | Points to '
- 'the execution frame of the current |\n'
- '| | level. '
- 'Accessing this attribute raises an |\n'
- '| | auditing '
- 'event "object.__getattr__" with arguments |\n'
- '| | "obj" and '
- '""tb_frame"". |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| traceback.tb_lineno | Gives the '
- 'line number where the exception occurred |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '| traceback.tb_lasti | Indicates '
- 'the “precise instruction”. |\n'
- '+----------------------------------------------------+----------------------------------------------------+\n'
- '\n'
- 'The line number and last instruction in the traceback may differ '
- 'from\n'
- 'the line number of its frame object if the exception occurred in a\n'
- '"try" statement with no matching except clause or with a "finally"\n'
- 'clause.\n'
- '\n'
- 'traceback.tb_next\n'
- '\n'
- ' The special writable attribute "tb_next" is the next level in '
- 'the\n'
- ' stack trace (towards the frame where the exception occurred), '
- 'or\n'
- ' "None" if there is no next level.\n'
- '\n'
- ' Changed in version 3.7: This attribute is now writable\n'
- '\n'
- '\n'
- 'Slice objects\n'
- '-------------\n'
- '\n'
- 'Slice objects are used to represent slices for "__getitem__()"\n'
- 'methods. They are also created by the built-in "slice()" '
- 'function.\n'
- '\n'
- 'Special read-only attributes: "start" is the lower bound; "stop" '
- 'is\n'
- 'the upper bound; "step" is the step value; each is "None" if '
- 'omitted.\n'
- 'These attributes can have any type.\n'
- '\n'
- 'Slice objects support one method:\n'
- '\n'
- 'slice.indices(self, length)\n'
- '\n'
- ' This method takes a single integer argument *length* and '
- 'computes\n'
- ' information about the slice that the slice object would describe '
- 'if\n'
- ' applied to a sequence of *length* items. It returns a tuple of\n'
- ' three integers; respectively these are the *start* and *stop*\n'
- ' indices and the *step* or stride length of the slice. Missing '
- 'or\n'
- ' out-of-bounds indices are handled in a manner consistent with\n'
- ' regular slices.\n'
- '\n'
- '\n'
- 'Static method objects\n'
- '---------------------\n'
- '\n'
- 'Static method objects provide a way of defeating the transformation '
- 'of\n'
- 'function objects to method objects described above. A static '
- 'method\n'
- 'object is a wrapper around any other object, usually a '
- 'user-defined\n'
- 'method object. When a static method object is retrieved from a '
- 'class\n'
- 'or a class instance, the object actually returned is the wrapped\n'
- 'object, which is not subject to any further transformation. Static\n'
- 'method objects are also callable. Static method objects are created '
- 'by\n'
- 'the built-in "staticmethod()" constructor.\n'
- '\n'
- '\n'
- 'Class method objects\n'
- '--------------------\n'
- '\n'
- 'A class method object, like a static method object, is a wrapper\n'
- 'around another object that alters the way in which that object is\n'
- 'retrieved from classes and class instances. The behaviour of class\n'
- 'method objects upon such retrieval is described above, under '
- '“instance\n'
- 'methods”. Class method objects are created by the built-in\n'
- '"classmethod()" constructor.\n',
- 'typesfunctions': 'Functions\n'
- '*********\n'
- '\n'
- 'Function objects are created by function definitions. The '
- 'only\n'
- 'operation on a function object is to call it: '
- '"func(argument-list)".\n'
- '\n'
- 'There are really two flavors of function objects: built-in '
- 'functions\n'
- 'and user-defined functions. Both support the same '
- 'operation (to call\n'
- 'the function), but the implementation is different, hence '
- 'the\n'
- 'different object types.\n'
- '\n'
- 'See Function definitions for more information.\n',
- 'typesmapping': 'Mapping Types — "dict"\n'
- '**********************\n'
- '\n'
- 'A *mapping* object maps *hashable* values to arbitrary '
- 'objects.\n'
- 'Mappings are mutable objects. There is currently only one '
- 'standard\n'
- 'mapping type, the *dictionary*. (For other containers see '
- 'the built-\n'
- 'in "list", "set", and "tuple" classes, and the "collections" '
- 'module.)\n'
- '\n'
- 'A dictionary’s keys are *almost* arbitrary values. Values '
- 'that are\n'
- 'not *hashable*, that is, values containing lists, '
- 'dictionaries or\n'
- 'other mutable types (that are compared by value rather than '
- 'by object\n'
- 'identity) may not be used as keys. Values that compare equal '
- '(such as\n'
- '"1", "1.0", and "True") can be used interchangeably to index '
- 'the same\n'
- 'dictionary entry.\n'
- '\n'
- 'class dict(**kwargs)\n'
- 'class dict(mapping, **kwargs)\n'
- 'class dict(iterable, **kwargs)\n'
- '\n'
- ' Return a new dictionary initialized from an optional '
- 'positional\n'
- ' argument and a possibly empty set of keyword arguments.\n'
- '\n'
- ' Dictionaries can be created by several means:\n'
- '\n'
- ' * Use a comma-separated list of "key: value" pairs within '
- 'braces:\n'
- ' "{\'jack\': 4098, \'sjoerd\': 4127}" or "{4098: '
- "'jack', 4127:\n"
- ' \'sjoerd\'}"\n'
- '\n'
- ' * Use a dict comprehension: "{}", "{x: x ** 2 for x in '
- 'range(10)}"\n'
- '\n'
- ' * Use the type constructor: "dict()", "dict([(\'foo\', '
- "100), ('bar',\n"
- ' 200)])", "dict(foo=100, bar=200)"\n'
- '\n'
- ' If no positional argument is given, an empty dictionary '
- 'is created.\n'
- ' If a positional argument is given and it defines a '
- '"keys()" method,\n'
- ' a dictionary is created by calling "__getitem__()" on the '
- 'argument\n'
- ' with each returned key from the method. Otherwise, the '
- 'positional\n'
- ' argument must be an *iterable* object. Each item in the '
- 'iterable\n'
- ' must itself be an iterable with exactly two elements. '
- 'The first\n'
- ' element of each item becomes a key in the new dictionary, '
- 'and the\n'
- ' second element the corresponding value. If a key occurs '
- 'more than\n'
- ' once, the last value for that key becomes the '
- 'corresponding value\n'
- ' in the new dictionary.\n'
- '\n'
- ' If keyword arguments are given, the keyword arguments and '
- 'their\n'
- ' values are added to the dictionary created from the '
- 'positional\n'
- ' argument. If a key being added is already present, the '
- 'value from\n'
- ' the keyword argument replaces the value from the '
- 'positional\n'
- ' argument.\n'
- '\n'
- ' To illustrate, the following examples all return a '
- 'dictionary equal\n'
- ' to "{"one": 1, "two": 2, "three": 3}":\n'
- '\n'
- ' >>> a = dict(one=1, two=2, three=3)\n'
- " >>> b = {'one': 1, 'two': 2, 'three': 3}\n"
- " >>> c = dict(zip(['one', 'two', 'three'], [1, 2, 3]))\n"
- " >>> d = dict([('two', 2), ('one', 1), ('three', 3)])\n"
- " >>> e = dict({'three': 3, 'one': 1, 'two': 2})\n"
- " >>> f = dict({'one': 1, 'three': 3}, two=2)\n"
- ' >>> a == b == c == d == e == f\n'
- ' True\n'
- '\n'
- ' Providing keyword arguments as in the first example only '
- 'works for\n'
- ' keys that are valid Python identifiers. Otherwise, any '
- 'valid keys\n'
- ' can be used.\n'
- '\n'
- ' These are the operations that dictionaries support (and '
- 'therefore,\n'
- ' custom mapping types should support too):\n'
- '\n'
- ' list(d)\n'
- '\n'
- ' Return a list of all the keys used in the dictionary '
- '*d*.\n'
- '\n'
- ' len(d)\n'
- '\n'
- ' Return the number of items in the dictionary *d*.\n'
- '\n'
- ' d[key]\n'
- '\n'
- ' Return the item of *d* with key *key*. Raises a '
- '"KeyError" if\n'
- ' *key* is not in the map.\n'
- '\n'
- ' If a subclass of dict defines a method "__missing__()" '
- 'and *key*\n'
- ' is not present, the "d[key]" operation calls that '
- 'method with\n'
- ' the key *key* as argument. The "d[key]" operation '
- 'then returns\n'
- ' or raises whatever is returned or raised by the\n'
- ' "__missing__(key)" call. No other operations or '
- 'methods invoke\n'
- ' "__missing__()". If "__missing__()" is not defined, '
- '"KeyError"\n'
- ' is raised. "__missing__()" must be a method; it cannot '
- 'be an\n'
- ' instance variable:\n'
- '\n'
- ' >>> class Counter(dict):\n'
- ' ... def __missing__(self, key):\n'
- ' ... return 0\n'
- ' ...\n'
- ' >>> c = Counter()\n'
- " >>> c['red']\n"
- ' 0\n'
- " >>> c['red'] += 1\n"
- " >>> c['red']\n"
- ' 1\n'
- '\n'
- ' The example above shows part of the implementation of\n'
- ' "collections.Counter". A different "__missing__" '
- 'method is used\n'
- ' by "collections.defaultdict".\n'
- '\n'
- ' d[key] = value\n'
- '\n'
- ' Set "d[key]" to *value*.\n'
- '\n'
- ' del d[key]\n'
- '\n'
- ' Remove "d[key]" from *d*. Raises a "KeyError" if '
- '*key* is not\n'
- ' in the map.\n'
- '\n'
- ' key in d\n'
- '\n'
- ' Return "True" if *d* has a key *key*, else "False".\n'
- '\n'
- ' key not in d\n'
- '\n'
- ' Equivalent to "not key in d".\n'
- '\n'
- ' iter(d)\n'
- '\n'
- ' Return an iterator over the keys of the dictionary. '
- 'This is a\n'
- ' shortcut for "iter(d.keys())".\n'
- '\n'
- ' clear()\n'
- '\n'
- ' Remove all items from the dictionary.\n'
- '\n'
- ' copy()\n'
- '\n'
- ' Return a shallow copy of the dictionary.\n'
- '\n'
- ' classmethod fromkeys(iterable, value=None, /)\n'
- '\n'
- ' Create a new dictionary with keys from *iterable* and '
- 'values set\n'
- ' to *value*.\n'
- '\n'
- ' "fromkeys()" is a class method that returns a new '
- 'dictionary.\n'
- ' *value* defaults to "None". All of the values refer '
- 'to just a\n'
- ' single instance, so it generally doesn’t make sense '
- 'for *value*\n'
- ' to be a mutable object such as an empty list. To get '
- 'distinct\n'
- ' values, use a dict comprehension instead.\n'
- '\n'
- ' get(key, default=None)\n'
- '\n'
- ' Return the value for *key* if *key* is in the '
- 'dictionary, else\n'
- ' *default*. If *default* is not given, it defaults to '
- '"None", so\n'
- ' that this method never raises a "KeyError".\n'
- '\n'
- ' items()\n'
- '\n'
- ' Return a new view of the dictionary’s items ("(key, '
- 'value)"\n'
- ' pairs). See the documentation of view objects.\n'
- '\n'
- ' keys()\n'
- '\n'
- ' Return a new view of the dictionary’s keys. See the\n'
- ' documentation of view objects.\n'
- '\n'
- ' pop(key[, default])\n'
- '\n'
- ' If *key* is in the dictionary, remove it and return '
- 'its value,\n'
- ' else return *default*. If *default* is not given and '
- '*key* is\n'
- ' not in the dictionary, a "KeyError" is raised.\n'
- '\n'
- ' popitem()\n'
- '\n'
- ' Remove and return a "(key, value)" pair from the '
- 'dictionary.\n'
- ' Pairs are returned in LIFO (last-in, first-out) '
- 'order.\n'
- '\n'
- ' "popitem()" is useful to destructively iterate over a\n'
- ' dictionary, as often used in set algorithms. If the '
- 'dictionary\n'
- ' is empty, calling "popitem()" raises a "KeyError".\n'
- '\n'
- ' Changed in version 3.7: LIFO order is now guaranteed. '
- 'In prior\n'
- ' versions, "popitem()" would return an arbitrary '
- 'key/value pair.\n'
- '\n'
- ' reversed(d)\n'
- '\n'
- ' Return a reverse iterator over the keys of the '
- 'dictionary. This\n'
- ' is a shortcut for "reversed(d.keys())".\n'
- '\n'
- ' Added in version 3.8.\n'
- '\n'
- ' setdefault(key, default=None)\n'
- '\n'
- ' If *key* is in the dictionary, return its value. If '
- 'not, insert\n'
- ' *key* with a value of *default* and return *default*. '
- '*default*\n'
- ' defaults to "None".\n'
- '\n'
- ' update([other])\n'
- '\n'
- ' Update the dictionary with the key/value pairs from '
- '*other*,\n'
- ' overwriting existing keys. Return "None".\n'
- '\n'
- ' "update()" accepts either another object with a '
- '"keys()" method\n'
- ' (in which case "__getitem__()" is called with every '
- 'key returned\n'
- ' from the method) or an iterable of key/value pairs (as '
- 'tuples or\n'
- ' other iterables of length two). If keyword arguments '
- 'are\n'
- ' specified, the dictionary is then updated with those '
- 'key/value\n'
- ' pairs: "d.update(red=1, blue=2)".\n'
- '\n'
- ' values()\n'
- '\n'
- ' Return a new view of the dictionary’s values. See '
- 'the\n'
- ' documentation of view objects.\n'
- '\n'
- ' An equality comparison between one "dict.values()" '
- 'view and\n'
- ' another will always return "False". This also applies '
- 'when\n'
- ' comparing "dict.values()" to itself:\n'
- '\n'
- " >>> d = {'a': 1}\n"
- ' >>> d.values() == d.values()\n'
- ' False\n'
- '\n'
- ' d | other\n'
- '\n'
- ' Create a new dictionary with the merged keys and '
- 'values of *d*\n'
- ' and *other*, which must both be dictionaries. The '
- 'values of\n'
- ' *other* take priority when *d* and *other* share '
- 'keys.\n'
- '\n'
- ' Added in version 3.9.\n'
- '\n'
- ' d |= other\n'
- '\n'
- ' Update the dictionary *d* with keys and values from '
- '*other*,\n'
- ' which may be either a *mapping* or an *iterable* of '
- 'key/value\n'
- ' pairs. The values of *other* take priority when *d* '
- 'and *other*\n'
- ' share keys.\n'
- '\n'
- ' Added in version 3.9.\n'
- '\n'
- ' Dictionaries compare equal if and only if they have the '
- 'same "(key,\n'
- ' value)" pairs (regardless of ordering). Order comparisons '
- '(‘<’,\n'
- ' ‘<=’, ‘>=’, ‘>’) raise "TypeError".\n'
- '\n'
- ' Dictionaries preserve insertion order. Note that '
- 'updating a key\n'
- ' does not affect the order. Keys added after deletion are '
- 'inserted\n'
- ' at the end.\n'
- '\n'
- ' >>> d = {"one": 1, "two": 2, "three": 3, "four": 4}\n'
- ' >>> d\n'
- " {'one': 1, 'two': 2, 'three': 3, 'four': 4}\n"
- ' >>> list(d)\n'
- " ['one', 'two', 'three', 'four']\n"
- ' >>> list(d.values())\n'
- ' [1, 2, 3, 4]\n'
- ' >>> d["one"] = 42\n'
- ' >>> d\n'
- " {'one': 42, 'two': 2, 'three': 3, 'four': 4}\n"
- ' >>> del d["two"]\n'
- ' >>> d["two"] = None\n'
- ' >>> d\n'
- " {'one': 42, 'three': 3, 'four': 4, 'two': None}\n"
- '\n'
- ' Changed in version 3.7: Dictionary order is guaranteed to '
- 'be\n'
- ' insertion order. This behavior was an implementation '
- 'detail of\n'
- ' CPython from 3.6.\n'
- '\n'
- ' Dictionaries and dictionary views are reversible.\n'
- '\n'
- ' >>> d = {"one": 1, "two": 2, "three": 3, "four": 4}\n'
- ' >>> d\n'
- " {'one': 1, 'two': 2, 'three': 3, 'four': 4}\n"
- ' >>> list(reversed(d))\n'
- " ['four', 'three', 'two', 'one']\n"
- ' >>> list(reversed(d.values()))\n'
- ' [4, 3, 2, 1]\n'
- ' >>> list(reversed(d.items()))\n'
- " [('four', 4), ('three', 3), ('two', 2), ('one', 1)]\n"
- '\n'
- ' Changed in version 3.8: Dictionaries are now reversible.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' "types.MappingProxyType" can be used to create a read-only '
- 'view of a\n'
- ' "dict".\n'
- '\n'
- '\n'
- 'Dictionary view objects\n'
- '=======================\n'
- '\n'
- 'The objects returned by "dict.keys()", "dict.values()" and\n'
- '"dict.items()" are *view objects*. They provide a dynamic '
- 'view on the\n'
- 'dictionary’s entries, which means that when the dictionary '
- 'changes,\n'
- 'the view reflects these changes.\n'
- '\n'
- 'Dictionary views can be iterated over to yield their '
- 'respective data,\n'
- 'and support membership tests:\n'
- '\n'
- 'len(dictview)\n'
- '\n'
- ' Return the number of entries in the dictionary.\n'
- '\n'
- 'iter(dictview)\n'
- '\n'
- ' Return an iterator over the keys, values or items '
- '(represented as\n'
- ' tuples of "(key, value)") in the dictionary.\n'
- '\n'
- ' Keys and values are iterated over in insertion order. '
- 'This allows\n'
- ' the creation of "(value, key)" pairs using "zip()": '
- '"pairs =\n'
- ' zip(d.values(), d.keys())". Another way to create the '
- 'same list is\n'
- ' "pairs = [(v, k) for (k, v) in d.items()]".\n'
- '\n'
- ' Iterating views while adding or deleting entries in the '
- 'dictionary\n'
- ' may raise a "RuntimeError" or fail to iterate over all '
- 'entries.\n'
- '\n'
- ' Changed in version 3.7: Dictionary order is guaranteed to '
- 'be\n'
- ' insertion order.\n'
- '\n'
- 'x in dictview\n'
- '\n'
- ' Return "True" if *x* is in the underlying dictionary’s '
- 'keys, values\n'
- ' or items (in the latter case, *x* should be a "(key, '
- 'value)"\n'
- ' tuple).\n'
- '\n'
- 'reversed(dictview)\n'
- '\n'
- ' Return a reverse iterator over the keys, values or items '
- 'of the\n'
- ' dictionary. The view will be iterated in reverse order of '
- 'the\n'
- ' insertion.\n'
- '\n'
- ' Changed in version 3.8: Dictionary views are now '
- 'reversible.\n'
- '\n'
- 'dictview.mapping\n'
- '\n'
- ' Return a "types.MappingProxyType" that wraps the '
- 'original\n'
- ' dictionary to which the view refers.\n'
- '\n'
- ' Added in version 3.10.\n'
- '\n'
- 'Keys views are set-like since their entries are unique and '
- '*hashable*.\n'
- 'Items views also have set-like operations since the (key, '
- 'value) pairs\n'
- 'are unique and the keys are hashable. If all values in an '
- 'items view\n'
- 'are hashable as well, then the items view can interoperate '
- 'with other\n'
- 'sets. (Values views are not treated as set-like since the '
- 'entries are\n'
- 'generally not unique.) For set-like views, all of the '
- 'operations\n'
- 'defined for the abstract base class "collections.abc.Set" '
- 'are\n'
- 'available (for example, "==", "<", or "^"). While using '
- 'set\n'
- 'operators, set-like views accept any iterable as the other '
- 'operand,\n'
- 'unlike sets which only accept sets as the input.\n'
- '\n'
- 'An example of dictionary view usage:\n'
- '\n'
- " >>> dishes = {'eggs': 2, 'sausage': 1, 'bacon': 1, "
- "'spam': 500}\n"
- ' >>> keys = dishes.keys()\n'
- ' >>> values = dishes.values()\n'
- '\n'
- ' >>> # iteration\n'
- ' >>> n = 0\n'
- ' >>> for val in values:\n'
- ' ... n += val\n'
- ' ...\n'
- ' >>> print(n)\n'
- ' 504\n'
- '\n'
- ' >>> # keys and values are iterated over in the same order '
- '(insertion order)\n'
- ' >>> list(keys)\n'
- " ['eggs', 'sausage', 'bacon', 'spam']\n"
- ' >>> list(values)\n'
- ' [2, 1, 1, 500]\n'
- '\n'
- ' >>> # view objects are dynamic and reflect dict changes\n'
- " >>> del dishes['eggs']\n"
- " >>> del dishes['sausage']\n"
- ' >>> list(keys)\n'
- " ['bacon', 'spam']\n"
- '\n'
- ' >>> # set operations\n'
- " >>> keys & {'eggs', 'bacon', 'salad'}\n"
- " {'bacon'}\n"
- " >>> keys ^ {'sausage', 'juice'} == {'juice', 'sausage', "
- "'bacon', 'spam'}\n"
- ' True\n'
- " >>> keys | ['juice', 'juice', 'juice'] == {'bacon', "
- "'spam', 'juice'}\n"
- ' True\n'
- '\n'
- ' >>> # get back a read-only proxy for the original '
- 'dictionary\n'
- ' >>> values.mapping\n'
- " mappingproxy({'bacon': 1, 'spam': 500})\n"
- " >>> values.mapping['spam']\n"
- ' 500\n',
- 'typesmethods': 'Methods\n'
- '*******\n'
- '\n'
- 'Methods are functions that are called using the attribute '
- 'notation.\n'
- 'There are two flavors: built-in methods (such as "append()" '
- 'on lists)\n'
- 'and class instance method. Built-in methods are described '
- 'with the\n'
- 'types that support them.\n'
- '\n'
- 'If you access a method (a function defined in a class '
- 'namespace)\n'
- 'through an instance, you get a special object: a *bound '
- 'method* (also\n'
- 'called instance method) object. When called, it will add the '
- '"self"\n'
- 'argument to the argument list. Bound methods have two '
- 'special read-\n'
- 'only attributes: "m.__self__" is the object on which the '
- 'method\n'
- 'operates, and "m.__func__" is the function implementing the '
- 'method.\n'
- 'Calling "m(arg-1, arg-2, ..., arg-n)" is completely '
- 'equivalent to\n'
- 'calling "m.__func__(m.__self__, arg-1, arg-2, ..., arg-n)".\n'
- '\n'
- 'Like function objects, bound method objects support getting '
- 'arbitrary\n'
- 'attributes. However, since method attributes are actually '
- 'stored on\n'
- 'the underlying function object ("method.__func__"), setting '
- 'method\n'
- 'attributes on bound methods is disallowed. Attempting to '
- 'set an\n'
- 'attribute on a method results in an "AttributeError" being '
- 'raised. In\n'
- 'order to set a method attribute, you need to explicitly set '
- 'it on the\n'
- 'underlying function object:\n'
- '\n'
- ' >>> class C:\n'
- ' ... def method(self):\n'
- ' ... pass\n'
- ' ...\n'
- ' >>> c = C()\n'
- " >>> c.method.whoami = 'my name is method' # can't set on "
- 'the method\n'
- ' Traceback (most recent call last):\n'
- ' File "<stdin>", line 1, in <module>\n'
- " AttributeError: 'method' object has no attribute "
- "'whoami'\n"
- " >>> c.method.__func__.whoami = 'my name is method'\n"
- ' >>> c.method.whoami\n'
- " 'my name is method'\n"
- '\n'
- 'See Instance methods for more information.\n',
- 'typesmodules': 'Modules\n'
- '*******\n'
- '\n'
- 'The only special operation on a module is attribute access: '
- '"m.name",\n'
- 'where *m* is a module and *name* accesses a name defined in '
- '*m*’s\n'
- 'symbol table. Module attributes can be assigned to. (Note '
- 'that the\n'
- '"import" statement is not, strictly speaking, an operation '
- 'on a module\n'
- 'object; "import foo" does not require a module object named '
- '*foo* to\n'
- 'exist, rather it requires an (external) *definition* for a '
- 'module\n'
- 'named *foo* somewhere.)\n'
- '\n'
- 'A special attribute of every module is "__dict__". This is '
- 'the\n'
- 'dictionary containing the module’s symbol table. Modifying '
- 'this\n'
- 'dictionary will actually change the module’s symbol table, '
- 'but direct\n'
- 'assignment to the "__dict__" attribute is not possible (you '
- 'can write\n'
- '"m.__dict__[\'a\'] = 1", which defines "m.a" to be "1", but '
- 'you can’t\n'
- 'write "m.__dict__ = {}"). Modifying "__dict__" directly is '
- 'not\n'
- 'recommended.\n'
- '\n'
- 'Modules built into the interpreter are written like this: '
- '"<module\n'
- '\'sys\' (built-in)>". If loaded from a file, they are '
- 'written as\n'
- '"<module \'os\' from '
- '\'/usr/local/lib/pythonX.Y/os.pyc\'>".\n',
- 'typesseq': 'Sequence Types — "list", "tuple", "range"\n'
- '*****************************************\n'
- '\n'
- 'There are three basic sequence types: lists, tuples, and range\n'
- 'objects. Additional sequence types tailored for processing of '
- 'binary\n'
- 'data and text strings are described in dedicated sections.\n'
- '\n'
- '\n'
- 'Common Sequence Operations\n'
- '==========================\n'
- '\n'
- 'The operations in the following table are supported by most '
- 'sequence\n'
- 'types, both mutable and immutable. The '
- '"collections.abc.Sequence" ABC\n'
- 'is provided to make it easier to correctly implement these '
- 'operations\n'
- 'on custom sequence types.\n'
- '\n'
- 'This table lists the sequence operations sorted in ascending '
- 'priority.\n'
- 'In the table, *s* and *t* are sequences of the same type, *n*, '
- '*i*,\n'
- '*j* and *k* are integers and *x* is an arbitrary object that '
- 'meets any\n'
- 'type and value restrictions imposed by *s*.\n'
- '\n'
- 'The "in" and "not in" operations have the same priorities as '
- 'the\n'
- 'comparison operations. The "+" (concatenation) and "*" '
- '(repetition)\n'
- 'operations have the same priority as the corresponding numeric\n'
- 'operations. [3]\n'
- '\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| Operation | Result '
- '| Notes |\n'
- '|============================|==================================|============|\n'
- '| "x in s" | "True" if an item of *s* is '
- '| (1) |\n'
- '| | equal to *x*, else "False" '
- '| |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| "x not in s" | "False" if an item of *s* is '
- '| (1) |\n'
- '| | equal to *x*, else "True" '
- '| |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| "s + t" | the concatenation of *s* and *t* '
- '| (6)(7) |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| "s * n" or "n * s" | equivalent to adding *s* to '
- '| (2)(7) |\n'
- '| | itself *n* times '
- '| |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| "s[i]" | *i*th item of *s*, origin 0 '
- '| (3) |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| "s[i:j]" | slice of *s* from *i* to *j* '
- '| (3)(4) |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| "s[i:j:k]" | slice of *s* from *i* to *j* '
- '| (3)(5) |\n'
- '| | with step *k* '
- '| |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| "len(s)" | length of *s* '
- '| |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| "min(s)" | smallest item of *s* '
- '| |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| "max(s)" | largest item of *s* '
- '| |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| "s.index(x[, i[, j]])" | index of the first occurrence of '
- '| (8) |\n'
- '| | *x* in *s* (at or after index '
- '| |\n'
- '| | *i* and before index *j*) '
- '| |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '| "s.count(x)" | total number of occurrences of '
- '| |\n'
- '| | *x* in *s* '
- '| |\n'
- '+----------------------------+----------------------------------+------------+\n'
- '\n'
- 'Sequences of the same type also support comparisons. In '
- 'particular,\n'
- 'tuples and lists are compared lexicographically by comparing\n'
- 'corresponding elements. This means that to compare equal, every\n'
- 'element must compare equal and the two sequences must be of the '
- 'same\n'
- 'type and have the same length. (For full details see '
- 'Comparisons in\n'
- 'the language reference.)\n'
- '\n'
- 'Forward and reversed iterators over mutable sequences access '
- 'values\n'
- 'using an index. That index will continue to march forward (or\n'
- 'backward) even if the underlying sequence is mutated. The '
- 'iterator\n'
- 'terminates only when an "IndexError" or a "StopIteration" is\n'
- 'encountered (or when the index drops below zero).\n'
- '\n'
- 'Notes:\n'
- '\n'
- '1. While the "in" and "not in" operations are used only for '
- 'simple\n'
- ' containment testing in the general case, some specialised '
- 'sequences\n'
- ' (such as "str", "bytes" and "bytearray") also use them for\n'
- ' subsequence testing:\n'
- '\n'
- ' >>> "gg" in "eggs"\n'
- ' True\n'
- '\n'
- '2. Values of *n* less than "0" are treated as "0" (which yields '
- 'an\n'
- ' empty sequence of the same type as *s*). Note that items in '
- 'the\n'
- ' sequence *s* are not copied; they are referenced multiple '
- 'times.\n'
- ' This often haunts new Python programmers; consider:\n'
- '\n'
- ' >>> lists = [[]] * 3\n'
- ' >>> lists\n'
- ' [[], [], []]\n'
- ' >>> lists[0].append(3)\n'
- ' >>> lists\n'
- ' [[3], [3], [3]]\n'
- '\n'
- ' What has happened is that "[[]]" is a one-element list '
- 'containing\n'
- ' an empty list, so all three elements of "[[]] * 3" are '
- 'references\n'
- ' to this single empty list. Modifying any of the elements of\n'
- ' "lists" modifies this single list. You can create a list of\n'
- ' different lists this way:\n'
- '\n'
- ' >>> lists = [[] for i in range(3)]\n'
- ' >>> lists[0].append(3)\n'
- ' >>> lists[1].append(5)\n'
- ' >>> lists[2].append(7)\n'
- ' >>> lists\n'
- ' [[3], [5], [7]]\n'
- '\n'
- ' Further explanation is available in the FAQ entry How do I '
- 'create a\n'
- ' multidimensional list?.\n'
- '\n'
- '3. If *i* or *j* is negative, the index is relative to the end '
- 'of\n'
- ' sequence *s*: "len(s) + i" or "len(s) + j" is substituted. '
- 'But\n'
- ' note that "-0" is still "0".\n'
- '\n'
- '4. The slice of *s* from *i* to *j* is defined as the sequence '
- 'of\n'
- ' items with index *k* such that "i <= k < j". If *i* or *j* '
- 'is\n'
- ' greater than "len(s)", use "len(s)". If *i* is omitted or '
- '"None",\n'
- ' use "0". If *j* is omitted or "None", use "len(s)". If *i* '
- 'is\n'
- ' greater than or equal to *j*, the slice is empty.\n'
- '\n'
- '5. The slice of *s* from *i* to *j* with step *k* is defined as '
- 'the\n'
- ' sequence of items with index "x = i + n*k" such that "0 <= n '
- '<\n'
- ' (j-i)/k". In other words, the indices are "i", "i+k", '
- '"i+2*k",\n'
- ' "i+3*k" and so on, stopping when *j* is reached (but never\n'
- ' including *j*). When *k* is positive, *i* and *j* are '
- 'reduced to\n'
- ' "len(s)" if they are greater. When *k* is negative, *i* and '
- '*j* are\n'
- ' reduced to "len(s) - 1" if they are greater. If *i* or *j* '
- 'are\n'
- ' omitted or "None", they become “end” values (which end '
- 'depends on\n'
- ' the sign of *k*). Note, *k* cannot be zero. If *k* is '
- '"None", it\n'
- ' is treated like "1".\n'
- '\n'
- '6. Concatenating immutable sequences always results in a new '
- 'object.\n'
- ' This means that building up a sequence by repeated '
- 'concatenation\n'
- ' will have a quadratic runtime cost in the total sequence '
- 'length.\n'
- ' To get a linear runtime cost, you must switch to one of the\n'
- ' alternatives below:\n'
- '\n'
- ' * if concatenating "str" objects, you can build a list and '
- 'use\n'
- ' "str.join()" at the end or else write to an "io.StringIO"\n'
- ' instance and retrieve its value when complete\n'
- '\n'
- ' * if concatenating "bytes" objects, you can similarly use\n'
- ' "bytes.join()" or "io.BytesIO", or you can do in-place\n'
- ' concatenation with a "bytearray" object. "bytearray" '
- 'objects are\n'
- ' mutable and have an efficient overallocation mechanism\n'
- '\n'
- ' * if concatenating "tuple" objects, extend a "list" instead\n'
- '\n'
- ' * for other types, investigate the relevant class '
- 'documentation\n'
- '\n'
- '7. Some sequence types (such as "range") only support item '
- 'sequences\n'
- ' that follow specific patterns, and hence don’t support '
- 'sequence\n'
- ' concatenation or repetition.\n'
- '\n'
- '8. "index" raises "ValueError" when *x* is not found in *s*. Not '
- 'all\n'
- ' implementations support passing the additional arguments *i* '
- 'and\n'
- ' *j*. These arguments allow efficient searching of subsections '
- 'of\n'
- ' the sequence. Passing the extra arguments is roughly '
- 'equivalent to\n'
- ' using "s[i:j].index(x)", only without copying any data and '
- 'with the\n'
- ' returned index being relative to the start of the sequence '
- 'rather\n'
- ' than the start of the slice.\n'
- '\n'
- '\n'
- 'Immutable Sequence Types\n'
- '========================\n'
- '\n'
- 'The only operation that immutable sequence types generally '
- 'implement\n'
- 'that is not also implemented by mutable sequence types is '
- 'support for\n'
- 'the "hash()" built-in.\n'
- '\n'
- 'This support allows immutable sequences, such as "tuple" '
- 'instances, to\n'
- 'be used as "dict" keys and stored in "set" and "frozenset" '
- 'instances.\n'
- '\n'
- 'Attempting to hash an immutable sequence that contains '
- 'unhashable\n'
- 'values will result in "TypeError".\n'
- '\n'
- '\n'
- 'Mutable Sequence Types\n'
- '======================\n'
- '\n'
- 'The operations in the following table are defined on mutable '
- 'sequence\n'
- 'types. The "collections.abc.MutableSequence" ABC is provided to '
- 'make\n'
- 'it easier to correctly implement these operations on custom '
- 'sequence\n'
- 'types.\n'
- '\n'
- 'In the table *s* is an instance of a mutable sequence type, *t* '
- 'is any\n'
- 'iterable object and *x* is an arbitrary object that meets any '
- 'type and\n'
- 'value restrictions imposed by *s* (for example, "bytearray" '
- 'only\n'
- 'accepts integers that meet the value restriction "0 <= x <= '
- '255").\n'
- '\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| Operation | '
- 'Result | Notes |\n'
- '|================================|==================================|=======================|\n'
- '| "s[i] = x" | item *i* of *s* is replaced '
- 'by | |\n'
- '| | '
- '*x* | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s[i:j] = t" | slice of *s* from *i* to *j* '
- 'is | |\n'
- '| | replaced by the contents of '
- 'the | |\n'
- '| | iterable '
- '*t* | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "del s[i:j]" | same as "s[i:j] = '
- '[]" | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s[i:j:k] = t" | the elements of "s[i:j:k]" '
- 'are | (1) |\n'
- '| | replaced by those of '
- '*t* | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "del s[i:j:k]" | removes the elements '
- 'of | |\n'
- '| | "s[i:j:k]" from the '
- 'list | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.append(x)" | appends *x* to the end of '
- 'the | |\n'
- '| | sequence (same '
- 'as | |\n'
- '| | "s[len(s):len(s)] = '
- '[x]") | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.clear()" | removes all items from *s* '
- '(same | (5) |\n'
- '| | as "del '
- 's[:]") | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.copy()" | creates a shallow copy of '
- '*s* | (5) |\n'
- '| | (same as '
- '"s[:]") | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.extend(t)" or "s += t" | extends *s* with the contents '
- 'of | |\n'
- '| | *t* (for the most part the '
- 'same | |\n'
- '| | as "s[len(s):len(s)] = '
- 't") | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s *= n" | updates *s* with its '
- 'contents | (6) |\n'
- '| | repeated *n* '
- 'times | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.insert(i, x)" | inserts *x* into *s* at '
- 'the | |\n'
- '| | index given by *i* (same '
- 'as | |\n'
- '| | "s[i:i] = '
- '[x]") | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.pop()" or "s.pop(i)" | retrieves the item at *i* '
- 'and | (2) |\n'
- '| | also removes it from '
- '*s* | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.remove(x)" | removes the first item from '
- '*s* | (3) |\n'
- '| | where "s[i]" is equal to '
- '*x* | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.reverse()" | reverses the items of *s* '
- 'in | (4) |\n'
- '| | '
- 'place | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '\n'
- 'Notes:\n'
- '\n'
- '1. If *k* is not equal to "1", *t* must have the same length as '
- 'the\n'
- ' slice it is replacing.\n'
- '\n'
- '2. The optional argument *i* defaults to "-1", so that by '
- 'default the\n'
- ' last item is removed and returned.\n'
- '\n'
- '3. "remove()" raises "ValueError" when *x* is not found in *s*.\n'
- '\n'
- '4. The "reverse()" method modifies the sequence in place for '
- 'economy\n'
- ' of space when reversing a large sequence. To remind users '
- 'that it\n'
- ' operates by side effect, it does not return the reversed '
- 'sequence.\n'
- '\n'
- '5. "clear()" and "copy()" are included for consistency with the\n'
- ' interfaces of mutable containers that don’t support slicing\n'
- ' operations (such as "dict" and "set"). "copy()" is not part '
- 'of the\n'
- ' "collections.abc.MutableSequence" ABC, but most concrete '
- 'mutable\n'
- ' sequence classes provide it.\n'
- '\n'
- ' Added in version 3.3: "clear()" and "copy()" methods.\n'
- '\n'
- '6. The value *n* is an integer, or an object implementing\n'
- ' "__index__()". Zero and negative values of *n* clear the '
- 'sequence.\n'
- ' Items in the sequence are not copied; they are referenced '
- 'multiple\n'
- ' times, as explained for "s * n" under Common Sequence '
- 'Operations.\n'
- '\n'
- '\n'
- 'Lists\n'
- '=====\n'
- '\n'
- 'Lists are mutable sequences, typically used to store collections '
- 'of\n'
- 'homogeneous items (where the precise degree of similarity will '
- 'vary by\n'
- 'application).\n'
- '\n'
- 'class list([iterable])\n'
- '\n'
- ' Lists may be constructed in several ways:\n'
- '\n'
- ' * Using a pair of square brackets to denote the empty list: '
- '"[]"\n'
- '\n'
- ' * Using square brackets, separating items with commas: "[a]", '
- '"[a,\n'
- ' b, c]"\n'
- '\n'
- ' * Using a list comprehension: "[x for x in iterable]"\n'
- '\n'
- ' * Using the type constructor: "list()" or "list(iterable)"\n'
- '\n'
- ' The constructor builds a list whose items are the same and in '
- 'the\n'
- ' same order as *iterable*’s items. *iterable* may be either '
- 'a\n'
- ' sequence, a container that supports iteration, or an '
- 'iterator\n'
- ' object. If *iterable* is already a list, a copy is made and\n'
- ' returned, similar to "iterable[:]". For example, '
- '"list(\'abc\')"\n'
- ' returns "[\'a\', \'b\', \'c\']" and "list( (1, 2, 3) )" '
- 'returns "[1, 2,\n'
- ' 3]". If no argument is given, the constructor creates a new '
- 'empty\n'
- ' list, "[]".\n'
- '\n'
- ' Many other operations also produce lists, including the '
- '"sorted()"\n'
- ' built-in.\n'
- '\n'
- ' Lists implement all of the common and mutable sequence '
- 'operations.\n'
- ' Lists also provide the following additional method:\n'
- '\n'
- ' sort(*, key=None, reverse=False)\n'
- '\n'
- ' This method sorts the list in place, using only "<" '
- 'comparisons\n'
- ' between items. Exceptions are not suppressed - if any '
- 'comparison\n'
- ' operations fail, the entire sort operation will fail (and '
- 'the\n'
- ' list will likely be left in a partially modified state).\n'
- '\n'
- ' "sort()" accepts two arguments that can only be passed by\n'
- ' keyword (keyword-only arguments):\n'
- '\n'
- ' *key* specifies a function of one argument that is used '
- 'to\n'
- ' extract a comparison key from each list element (for '
- 'example,\n'
- ' "key=str.lower"). The key corresponding to each item in '
- 'the list\n'
- ' is calculated once and then used for the entire sorting '
- 'process.\n'
- ' The default value of "None" means that list items are '
- 'sorted\n'
- ' directly without calculating a separate key value.\n'
- '\n'
- ' The "functools.cmp_to_key()" utility is available to '
- 'convert a\n'
- ' 2.x style *cmp* function to a *key* function.\n'
- '\n'
- ' *reverse* is a boolean value. If set to "True", then the '
- 'list\n'
- ' elements are sorted as if each comparison were reversed.\n'
- '\n'
- ' This method modifies the sequence in place for economy of '
- 'space\n'
- ' when sorting a large sequence. To remind users that it '
- 'operates\n'
- ' by side effect, it does not return the sorted sequence '
- '(use\n'
- ' "sorted()" to explicitly request a new sorted list '
- 'instance).\n'
- '\n'
- ' The "sort()" method is guaranteed to be stable. A sort '
- 'is\n'
- ' stable if it guarantees not to change the relative order '
- 'of\n'
- ' elements that compare equal — this is helpful for sorting '
- 'in\n'
- ' multiple passes (for example, sort by department, then by '
- 'salary\n'
- ' grade).\n'
- '\n'
- ' For sorting examples and a brief sorting tutorial, see '
- 'Sorting\n'
- ' Techniques.\n'
- '\n'
- ' **CPython implementation detail:** While a list is being '
- 'sorted,\n'
- ' the effect of attempting to mutate, or even inspect, the '
- 'list is\n'
- ' undefined. The C implementation of Python makes the list '
- 'appear\n'
- ' empty for the duration, and raises "ValueError" if it can '
- 'detect\n'
- ' that the list has been mutated during a sort.\n'
- '\n'
- '\n'
- 'Tuples\n'
- '======\n'
- '\n'
- 'Tuples are immutable sequences, typically used to store '
- 'collections of\n'
- 'heterogeneous data (such as the 2-tuples produced by the '
- '"enumerate()"\n'
- 'built-in). Tuples are also used for cases where an immutable '
- 'sequence\n'
- 'of homogeneous data is needed (such as allowing storage in a '
- '"set" or\n'
- '"dict" instance).\n'
- '\n'
- 'class tuple([iterable])\n'
- '\n'
- ' Tuples may be constructed in a number of ways:\n'
- '\n'
- ' * Using a pair of parentheses to denote the empty tuple: '
- '"()"\n'
- '\n'
- ' * Using a trailing comma for a singleton tuple: "a," or '
- '"(a,)"\n'
- '\n'
- ' * Separating items with commas: "a, b, c" or "(a, b, c)"\n'
- '\n'
- ' * Using the "tuple()" built-in: "tuple()" or '
- '"tuple(iterable)"\n'
- '\n'
- ' The constructor builds a tuple whose items are the same and '
- 'in the\n'
- ' same order as *iterable*’s items. *iterable* may be either '
- 'a\n'
- ' sequence, a container that supports iteration, or an '
- 'iterator\n'
- ' object. If *iterable* is already a tuple, it is returned\n'
- ' unchanged. For example, "tuple(\'abc\')" returns "(\'a\', '
- '\'b\', \'c\')"\n'
- ' and "tuple( [1, 2, 3] )" returns "(1, 2, 3)". If no argument '
- 'is\n'
- ' given, the constructor creates a new empty tuple, "()".\n'
- '\n'
- ' Note that it is actually the comma which makes a tuple, not '
- 'the\n'
- ' parentheses. The parentheses are optional, except in the '
- 'empty\n'
- ' tuple case, or when they are needed to avoid syntactic '
- 'ambiguity.\n'
- ' For example, "f(a, b, c)" is a function call with three '
- 'arguments,\n'
- ' while "f((a, b, c))" is a function call with a 3-tuple as the '
- 'sole\n'
- ' argument.\n'
- '\n'
- ' Tuples implement all of the common sequence operations.\n'
- '\n'
- 'For heterogeneous collections of data where access by name is '
- 'clearer\n'
- 'than access by index, "collections.namedtuple()" may be a more\n'
- 'appropriate choice than a simple tuple object.\n'
- '\n'
- '\n'
- 'Ranges\n'
- '======\n'
- '\n'
- 'The "range" type represents an immutable sequence of numbers and '
- 'is\n'
- 'commonly used for looping a specific number of times in "for" '
- 'loops.\n'
- '\n'
- 'class range(stop)\n'
- 'class range(start, stop[, step])\n'
- '\n'
- ' The arguments to the range constructor must be integers '
- '(either\n'
- ' built-in "int" or any object that implements the '
- '"__index__()"\n'
- ' special method). If the *step* argument is omitted, it '
- 'defaults to\n'
- ' "1". If the *start* argument is omitted, it defaults to "0". '
- 'If\n'
- ' *step* is zero, "ValueError" is raised.\n'
- '\n'
- ' For a positive *step*, the contents of a range "r" are '
- 'determined\n'
- ' by the formula "r[i] = start + step*i" where "i >= 0" and '
- '"r[i] <\n'
- ' stop".\n'
- '\n'
- ' For a negative *step*, the contents of the range are still\n'
- ' determined by the formula "r[i] = start + step*i", but the\n'
- ' constraints are "i >= 0" and "r[i] > stop".\n'
- '\n'
- ' A range object will be empty if "r[0]" does not meet the '
- 'value\n'
- ' constraint. Ranges do support negative indices, but these '
- 'are\n'
- ' interpreted as indexing from the end of the sequence '
- 'determined by\n'
- ' the positive indices.\n'
- '\n'
- ' Ranges containing absolute values larger than "sys.maxsize" '
- 'are\n'
- ' permitted but some features (such as "len()") may raise\n'
- ' "OverflowError".\n'
- '\n'
- ' Range examples:\n'
- '\n'
- ' >>> list(range(10))\n'
- ' [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n'
- ' >>> list(range(1, 11))\n'
- ' [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]\n'
- ' >>> list(range(0, 30, 5))\n'
- ' [0, 5, 10, 15, 20, 25]\n'
- ' >>> list(range(0, 10, 3))\n'
- ' [0, 3, 6, 9]\n'
- ' >>> list(range(0, -10, -1))\n'
- ' [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]\n'
- ' >>> list(range(0))\n'
- ' []\n'
- ' >>> list(range(1, 0))\n'
- ' []\n'
- '\n'
- ' Ranges implement all of the common sequence operations '
- 'except\n'
- ' concatenation and repetition (due to the fact that range '
- 'objects\n'
- ' can only represent sequences that follow a strict pattern '
- 'and\n'
- ' repetition and concatenation will usually violate that '
- 'pattern).\n'
- '\n'
- ' start\n'
- '\n'
- ' The value of the *start* parameter (or "0" if the '
- 'parameter was\n'
- ' not supplied)\n'
- '\n'
- ' stop\n'
- '\n'
- ' The value of the *stop* parameter\n'
- '\n'
- ' step\n'
- '\n'
- ' The value of the *step* parameter (or "1" if the parameter '
- 'was\n'
- ' not supplied)\n'
- '\n'
- 'The advantage of the "range" type over a regular "list" or '
- '"tuple" is\n'
- 'that a "range" object will always take the same (small) amount '
- 'of\n'
- 'memory, no matter the size of the range it represents (as it '
- 'only\n'
- 'stores the "start", "stop" and "step" values, calculating '
- 'individual\n'
- 'items and subranges as needed).\n'
- '\n'
- 'Range objects implement the "collections.abc.Sequence" ABC, and\n'
- 'provide features such as containment tests, element index '
- 'lookup,\n'
- 'slicing and support for negative indices (see Sequence Types — '
- 'list,\n'
- 'tuple, range):\n'
- '\n'
- '>>> r = range(0, 20, 2)\n'
- '>>> r\n'
- 'range(0, 20, 2)\n'
- '>>> 11 in r\n'
- 'False\n'
- '>>> 10 in r\n'
- 'True\n'
- '>>> r.index(10)\n'
- '5\n'
- '>>> r[5]\n'
- '10\n'
- '>>> r[:5]\n'
- 'range(0, 10, 2)\n'
- '>>> r[-1]\n'
- '18\n'
- '\n'
- 'Testing range objects for equality with "==" and "!=" compares '
- 'them as\n'
- 'sequences. That is, two range objects are considered equal if '
- 'they\n'
- 'represent the same sequence of values. (Note that two range '
- 'objects\n'
- 'that compare equal might have different "start", "stop" and '
- '"step"\n'
- 'attributes, for example "range(0) == range(2, 1, 3)" or '
- '"range(0, 3,\n'
- '2) == range(0, 4, 2)".)\n'
- '\n'
- 'Changed in version 3.2: Implement the Sequence ABC. Support '
- 'slicing\n'
- 'and negative indices. Test "int" objects for membership in '
- 'constant\n'
- 'time instead of iterating through all items.\n'
- '\n'
- 'Changed in version 3.3: Define ‘==’ and ‘!=’ to compare range '
- 'objects\n'
- 'based on the sequence of values they define (instead of '
- 'comparing\n'
- 'based on object identity).Added the "start", "stop" and "step"\n'
- 'attributes.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' * The linspace recipe shows how to implement a lazy version of '
- 'range\n'
- ' suitable for floating-point applications.\n',
- 'typesseq-mutable': 'Mutable Sequence Types\n'
- '**********************\n'
- '\n'
- 'The operations in the following table are defined on '
- 'mutable sequence\n'
- 'types. The "collections.abc.MutableSequence" ABC is '
- 'provided to make\n'
- 'it easier to correctly implement these operations on '
- 'custom sequence\n'
- 'types.\n'
- '\n'
- 'In the table *s* is an instance of a mutable sequence '
- 'type, *t* is any\n'
- 'iterable object and *x* is an arbitrary object that '
- 'meets any type and\n'
- 'value restrictions imposed by *s* (for example, '
- '"bytearray" only\n'
- 'accepts integers that meet the value restriction "0 <= x '
- '<= 255").\n'
- '\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| Operation | '
- 'Result | Notes '
- '|\n'
- '|================================|==================================|=======================|\n'
- '| "s[i] = x" | item *i* of *s* is '
- 'replaced by | |\n'
- '| | '
- '*x* | '
- '|\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s[i:j] = t" | slice of *s* from *i* '
- 'to *j* is | |\n'
- '| | replaced by the '
- 'contents of the | |\n'
- '| | iterable '
- '*t* | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "del s[i:j]" | same as "s[i:j] = '
- '[]" | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s[i:j:k] = t" | the elements of '
- '"s[i:j:k]" are | (1) |\n'
- '| | replaced by those of '
- '*t* | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "del s[i:j:k]" | removes the elements '
- 'of | |\n'
- '| | "s[i:j:k]" from the '
- 'list | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.append(x)" | appends *x* to the '
- 'end of the | |\n'
- '| | sequence (same '
- 'as | |\n'
- '| | "s[len(s):len(s)] = '
- '[x]") | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.clear()" | removes all items '
- 'from *s* (same | (5) |\n'
- '| | as "del '
- 's[:]") | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.copy()" | creates a shallow '
- 'copy of *s* | (5) |\n'
- '| | (same as '
- '"s[:]") | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.extend(t)" or "s += t" | extends *s* with the '
- 'contents of | |\n'
- '| | *t* (for the most '
- 'part the same | |\n'
- '| | as "s[len(s):len(s)] '
- '= t") | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s *= n" | updates *s* with its '
- 'contents | (6) |\n'
- '| | repeated *n* '
- 'times | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.insert(i, x)" | inserts *x* into *s* '
- 'at the | |\n'
- '| | index given by *i* '
- '(same as | |\n'
- '| | "s[i:i] = '
- '[x]") | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.pop()" or "s.pop(i)" | retrieves the item at '
- '*i* and | (2) |\n'
- '| | also removes it from '
- '*s* | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.remove(x)" | removes the first '
- 'item from *s* | (3) |\n'
- '| | where "s[i]" is equal '
- 'to *x* | |\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '| "s.reverse()" | reverses the items of '
- '*s* in | (4) |\n'
- '| | '
- 'place | '
- '|\n'
- '+--------------------------------+----------------------------------+-----------------------+\n'
- '\n'
- 'Notes:\n'
- '\n'
- '1. If *k* is not equal to "1", *t* must have the same '
- 'length as the\n'
- ' slice it is replacing.\n'
- '\n'
- '2. The optional argument *i* defaults to "-1", so that '
- 'by default the\n'
- ' last item is removed and returned.\n'
- '\n'
- '3. "remove()" raises "ValueError" when *x* is not found '
- 'in *s*.\n'
- '\n'
- '4. The "reverse()" method modifies the sequence in place '
- 'for economy\n'
- ' of space when reversing a large sequence. To remind '
- 'users that it\n'
- ' operates by side effect, it does not return the '
- 'reversed sequence.\n'
- '\n'
- '5. "clear()" and "copy()" are included for consistency '
- 'with the\n'
- ' interfaces of mutable containers that don’t support '
- 'slicing\n'
- ' operations (such as "dict" and "set"). "copy()" is '
- 'not part of the\n'
- ' "collections.abc.MutableSequence" ABC, but most '
- 'concrete mutable\n'
- ' sequence classes provide it.\n'
- '\n'
- ' Added in version 3.3: "clear()" and "copy()" '
- 'methods.\n'
- '\n'
- '6. The value *n* is an integer, or an object '
- 'implementing\n'
- ' "__index__()". Zero and negative values of *n* clear '
- 'the sequence.\n'
- ' Items in the sequence are not copied; they are '
- 'referenced multiple\n'
- ' times, as explained for "s * n" under Common Sequence '
- 'Operations.\n',
- 'unary': 'Unary arithmetic and bitwise operations\n'
- '***************************************\n'
- '\n'
- 'All unary arithmetic and bitwise operations have the same '
- 'priority:\n'
- '\n'
- ' u_expr ::= power | "-" u_expr | "+" u_expr | "~" u_expr\n'
- '\n'
- 'The unary "-" (minus) operator yields the negation of its numeric\n'
- 'argument; the operation can be overridden with the "__neg__()" '
- 'special\n'
- 'method.\n'
- '\n'
- 'The unary "+" (plus) operator yields its numeric argument '
- 'unchanged;\n'
- 'the operation can be overridden with the "__pos__()" special '
- 'method.\n'
- '\n'
- 'The unary "~" (invert) operator yields the bitwise inversion of '
- 'its\n'
- 'integer argument. The bitwise inversion of "x" is defined as\n'
- '"-(x+1)". It only applies to integral numbers or to custom '
- 'objects\n'
- 'that override the "__invert__()" special method.\n'
- '\n'
- 'In all three cases, if the argument does not have the proper type, '
- 'a\n'
- '"TypeError" exception is raised.\n',
- 'while': 'The "while" statement\n'
- '*********************\n'
- '\n'
- 'The "while" statement is used for repeated execution as long as an\n'
- 'expression is true:\n'
- '\n'
- ' while_stmt ::= "while" assignment_expression ":" suite\n'
- ' ["else" ":" suite]\n'
- '\n'
- 'This repeatedly tests the expression and, if it is true, executes '
- 'the\n'
- 'first suite; if the expression is false (which may be the first '
- 'time\n'
- 'it is tested) the suite of the "else" clause, if present, is '
- 'executed\n'
- 'and the loop terminates.\n'
- '\n'
- 'A "break" statement executed in the first suite terminates the '
- 'loop\n'
- 'without executing the "else" clause’s suite. A "continue" '
- 'statement\n'
- 'executed in the first suite skips the rest of the suite and goes '
- 'back\n'
- 'to testing the expression.\n',
- 'with': 'The "with" statement\n'
- '********************\n'
- '\n'
- 'The "with" statement is used to wrap the execution of a block with\n'
- 'methods defined by a context manager (see section With Statement\n'
- 'Context Managers). This allows common "try"…"except"…"finally" '
- 'usage\n'
- 'patterns to be encapsulated for convenient reuse.\n'
- '\n'
- ' with_stmt ::= "with" ( "(" with_stmt_contents ","? ")" | '
- 'with_stmt_contents ) ":" suite\n'
- ' with_stmt_contents ::= with_item ("," with_item)*\n'
- ' with_item ::= expression ["as" target]\n'
- '\n'
- 'The execution of the "with" statement with one “item” proceeds as\n'
- 'follows:\n'
- '\n'
- '1. The context expression (the expression given in the "with_item") '
- 'is\n'
- ' evaluated to obtain a context manager.\n'
- '\n'
- '2. The context manager’s "__enter__()" is loaded for later use.\n'
- '\n'
- '3. The context manager’s "__exit__()" is loaded for later use.\n'
- '\n'
- '4. The context manager’s "__enter__()" method is invoked.\n'
- '\n'
- '5. If a target was included in the "with" statement, the return '
- 'value\n'
- ' from "__enter__()" is assigned to it.\n'
- '\n'
- ' Note:\n'
- '\n'
- ' The "with" statement guarantees that if the "__enter__()" '
- 'method\n'
- ' returns without an error, then "__exit__()" will always be\n'
- ' called. Thus, if an error occurs during the assignment to the\n'
- ' target list, it will be treated the same as an error occurring\n'
- ' within the suite would be. See step 7 below.\n'
- '\n'
- '6. The suite is executed.\n'
- '\n'
- '7. The context manager’s "__exit__()" method is invoked. If an\n'
- ' exception caused the suite to be exited, its type, value, and\n'
- ' traceback are passed as arguments to "__exit__()". Otherwise, '
- 'three\n'
- ' "None" arguments are supplied.\n'
- '\n'
- ' If the suite was exited due to an exception, and the return '
- 'value\n'
- ' from the "__exit__()" method was false, the exception is '
- 'reraised.\n'
- ' If the return value was true, the exception is suppressed, and\n'
- ' execution continues with the statement following the "with"\n'
- ' statement.\n'
- '\n'
- ' If the suite was exited for any reason other than an exception, '
- 'the\n'
- ' return value from "__exit__()" is ignored, and execution '
- 'proceeds\n'
- ' at the normal location for the kind of exit that was taken.\n'
- '\n'
- 'The following code:\n'
- '\n'
- ' with EXPRESSION as TARGET:\n'
- ' SUITE\n'
- '\n'
- 'is semantically equivalent to:\n'
- '\n'
- ' manager = (EXPRESSION)\n'
- ' enter = type(manager).__enter__\n'
- ' exit = type(manager).__exit__\n'
- ' value = enter(manager)\n'
- ' hit_except = False\n'
- '\n'
- ' try:\n'
- ' TARGET = value\n'
- ' SUITE\n'
- ' except:\n'
- ' hit_except = True\n'
- ' if not exit(manager, *sys.exc_info()):\n'
- ' raise\n'
- ' finally:\n'
- ' if not hit_except:\n'
- ' exit(manager, None, None, None)\n'
- '\n'
- 'With more than one item, the context managers are processed as if\n'
- 'multiple "with" statements were nested:\n'
- '\n'
- ' with A() as a, B() as b:\n'
- ' SUITE\n'
- '\n'
- 'is semantically equivalent to:\n'
- '\n'
- ' with A() as a:\n'
- ' with B() as b:\n'
- ' SUITE\n'
- '\n'
- 'You can also write multi-item context managers in multiple lines if\n'
- 'the items are surrounded by parentheses. For example:\n'
- '\n'
- ' with (\n'
- ' A() as a,\n'
- ' B() as b,\n'
- ' ):\n'
- ' SUITE\n'
- '\n'
- 'Changed in version 3.1: Support for multiple context expressions.\n'
- '\n'
- 'Changed in version 3.10: Support for using grouping parentheses to\n'
- 'break the statement in multiple lines.\n'
- '\n'
- 'See also:\n'
- '\n'
- ' **PEP 343** - The “with” statement\n'
- ' The specification, background, and examples for the Python '
- '"with"\n'
- ' statement.\n',
- 'yield': 'The "yield" statement\n'
- '*********************\n'
- '\n'
- ' yield_stmt ::= yield_expression\n'
- '\n'
- 'A "yield" statement is semantically equivalent to a yield '
- 'expression.\n'
- 'The "yield" statement can be used to omit the parentheses that '
- 'would\n'
- 'otherwise be required in the equivalent yield expression '
- 'statement.\n'
- 'For example, the yield statements\n'
- '\n'
- ' yield <expr>\n'
- ' yield from <expr>\n'
- '\n'
- 'are equivalent to the yield expression statements\n'
- '\n'
- ' (yield <expr>)\n'
- ' (yield from <expr>)\n'
- '\n'
- 'Yield expressions and statements are only used when defining a\n'
- '*generator* function, and are only used in the body of the '
- 'generator\n'
- 'function. Using "yield" in a function definition is sufficient to\n'
- 'cause that definition to create a generator function instead of a\n'
- 'normal function.\n'
- '\n'
- 'For full details of "yield" semantics, refer to the Yield '
- 'expressions\n'
- 'section.\n'}
|