ydb/yql/essentials/tests/s-expressions/suites/Udf/PythonAvg.yqls

(
(let config (DataSource 'config))

# prepare python udf
(let ui32 (DataType 'Uint32))
(let dbl (DataType 'Double))
(let rt (ResourceType 'Python2))

(let udfScript (String '@@
class AvgCalc:
    def __init__(self):
        self.__count = 0
        self.__sum = 0

    def add(self, value):
        self.__sum = self.__sum + value
        self.__count = self.__count + 1

    def result(self):
        return self.__sum / float(self.__count)

def avg_create():
    return AvgCalc()

def avg_add(avg, value):
    avg.add(value)
    return avg

def avg_result(avg):
    return avg.result()

@@))

(let avgCreate (ScriptUdf 'Python3 'avg_create (CallableType '() '(rt)) udfScript))
(let avgAdd (ScriptUdf 'Python3 'avg_add (CallableType '() '(rt) '(rt) '(ui32)) udfScript))
(let avgResult (ScriptUdf 'Python3 'avg_result (CallableType '() '(dbl) '(rt)) udfScript))

# data
(let x (Uint32 '10))
(let y (Uint32 '30))
(let z (Uint32 '5))

# call udfs
(let avg (Apply avgCreate))
(let avg (Apply avgAdd avg x))
(let avg (Apply avgAdd avg y))
(let avg (Apply avgAdd avg z))
(let result (Apply avgResult avg))

# output result with type
(let res_sink (DataSink 'result))
(let world (Write! world res_sink (Key) result '( '('type) )))

# finish
(return (Commit! world res_sink))
)