ydb/contrib/deprecated/python/configparser

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The ancient ``ConfigParser`` module available in the standard library 2.x has
seen a major update in Python 3.2. This is a backport of those changes so that
they can be used directly in Python 2.6 - 3.5.

To use the ``configparser`` backport instead of the built-in version on both
Python 2 and Python 3, simply import it explicitly as a backport::

from backports import configparser

If you'd like to use the backport on Python 2 and the built-in version on
Python 3, use that invocation instead::

import configparser

For detailed documentation consult the vanilla version at
http://docs.python.org/3/library/configparser.html.

Why you'll love ``configparser``
--------------------------------

Whereas almost completely compatible with its older brother, ``configparser``
sports a bunch of interesting new features:

* full mapping protocol access (`more info
`_)::

>>> parser = ConfigParser()
>>> parser.read_string("""
[DEFAULT]
location = upper left
visible = yes
editable = no
color = blue

[main]
title = Main Menu
color = green

[options]
title = Options
""")
>>> parser['main']['color']
'green'
>>> parser['main']['editable']
'no'
>>> section = parser['options']
>>> section['title']
'Options'
>>> section['title'] = 'Options (editable: %(editable)s)'
>>> section['title']
'Options (editable: no)'

* there's now one default ``ConfigParser`` class, which basically is the old
``SafeConfigParser`` with a bunch of tweaks which make it more predictable for
users. Don't need interpolation? Simply use
``ConfigParser(interpolation=None)``, no need to use a distinct
``RawConfigParser`` anymore.

* the parser is highly `customizable upon instantiation
`__
supporting things like changing option delimiters, comment characters, the
name of the DEFAULT section, the interpolation syntax, etc.

* you can easily create your own interpolation syntax but there are two powerful
implementations built-in (`more info
`__):

* the classic ``%(string-like)s`` syntax (called ``BasicInterpolation``)

* a new ``${buildout:like}`` syntax (called ``ExtendedInterpolation``)

* fallback values may be specified in getters (`more info
`__)::

>>> config.get('closet', 'monster',
... fallback='No such things as monsters')
'No such things as monsters'

* ``ConfigParser`` objects can now read data directly `from strings
`__
and `from dictionaries
`__.
That means importing configuration from JSON or specifying default values for
the whole configuration (multiple sections) is now a single line of code. Same
goes for copying data from another ``ConfigParser`` instance, thanks to its
mapping protocol support.

* many smaller tweaks, updates and fixes

A few words about Unicode
-------------------------

``configparser`` comes from Python 3 and as such it works well with Unicode.
The library is generally cleaned up in terms of internal data storage and
reading/writing files. There are a couple of incompatibilities with the old
``ConfigParser`` due to that. However, the work required to migrate is well
worth it as it shows the issues that would likely come up during migration of
your project to Python 3.

The design assumes that Unicode strings are used whenever possible [1]_. That
gives you the certainty that what's stored in a configuration object is text.
Once your configuration is read, the rest of your application doesn't have to
deal with encoding issues. All you have is text [2]_. The only two phases when
you should explicitly state encoding is when you either read from an external
source (e.g. a file) or write back.

Versioning
----------

This project uses `semver `_ to
communicate the impact of various releases while periodically syncing
with the upstream implementation in CPython.
`The changelog `_
serves as a reference indicating which versions incorporate
which upstream functionality.

Prior to the ``4.0.0`` release, `another scheme
`_
was used to associate the CPython and backports releases.

Maintenance
-----------

This backport was originally authored by Łukasz Langa, the current vanilla
``configparser`` maintainer for CPython and is currently maintained by
Jason R. Coombs:

* `configparser repository `_

* `configparser issue tracker `_

Security Contact
----------------

To report a security vulnerability, please use the
`Tidelift security contact `_.
Tidelift will coordinate the fix and disclosure.

Conversion Process
------------------

This section is technical and should bother you only if you are wondering how
this backport is produced. If the implementation details of this backport are
not important for you, feel free to ignore the following content.

``configparser`` is converted using `python-future
`_. The project takes the following
branching approach:

* the ``3.x`` branch holds unchanged files synchronized from the upstream
CPython repository. The synchronization is currently done by manually copying
the required files and stating from which CPython changeset they come from.

* the ``master`` branch holds a version of the ``3.x`` code with some tweaks
that make it independent from libraries and constructions unavailable on 2.x.
Code on this branch still *must* work on the corresponding Python 3.x but
will also work on Python 2.6 and 2.7 (including PyPy). You can check this
running the supplied unit tests with ``tox``.

The process works like this:

1. In the ``3.x`` branch, run ``pip-run -- sync-upstream.py``, which
downloads the latest stable release of Python and copies the relevant
files from there into their new locations here and then commits those
changes with a nice reference to the relevant upstream commit hash.

2. I check for new names in ``__all__`` and update imports in
``configparser.py`` accordingly. I run the tests on Python 3. Commit.

3. I merge the new commit to ``master``. I run ``tox``. Commit.

4. If there are necessary changes, I do them now (on ``master``). Note that
the changes should be written in the syntax subset supported by Python
2.6.

5. I run ``tox``. If it works, I update the docs and release the new version.
Otherwise, I go back to point 3. I might use ``pasteurize`` to suggest me
required changes but usually I do them manually to keep resulting code in
a nicer form.


Footnotes
---------

.. [1] To somewhat ease migration, passing bytestrings is still supported but
they are converted to Unicode for internal storage anyway. This means
that for the vast majority of strings used in configuration files, it
won't matter if you pass them as bytestrings or Unicode. However, if you
pass a bytestring that cannot be converted to Unicode using the naive
ASCII codec, a ``UnicodeDecodeError`` will be raised. This is purposeful
and helps you manage proper encoding for all content you store in
memory, read from various sources and write back.

.. [2] Life gets much easier when you understand that you basically manage
**text** in your application. You don't care about bytes but about
letters. In that regard the concept of content encoding is meaningless.
The only time when you deal with raw bytes is when you write the data to
a file. Then you have to specify how your text should be encoded. On
the other end, to get meaningful text from a file, the application
reading it has to know which encoding was used during its creation. But
once the bytes are read and properly decoded, all you have is text. This
is especially powerful when you start interacting with multiple data
sources. Even if each of them uses a different encoding, inside your
application data is held in abstract text form. You can program your
business logic without worrying about which data came from which source.
You can freely exchange the data you store between sources. Only
reading/writing files requires encoding your text to bytes.