The Python Oracle

Override Python's 'in' operator?

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Track title: CC M Beethoven - Piano Sonata No 3 in C 3

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Chapters
00:00 Question
00:24 Accepted answer (Score 332)
00:38 Answer 2 (Score 269)
01:10 Answer 3 (Score 2)
01:36 Thank you

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Full question
https://stackoverflow.com/questions/2217...

Accepted answer links:
[MyClass.__contains__(self, item)]: http://docs.python.org/reference/datamod...

Answer 2 links:
[documentation on overloading ]: http://docs.python.org/reference/datamod...

Answer 3 links:
[__iter__]: https://docs.python.org/3/reference/data...

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Content licensed under CC BY-SA
https://meta.stackexchange.com/help/lice...

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Tags
#python #operatoroverloading #operators #inoperator

#avk47



ACCEPTED ANSWER

Score 359


MyClass.__contains__(self, item)




ANSWER 2

Score 280


A more complete answer is:

class MyClass(object):

    def __init__(self):
        self.numbers = [1,2,3,4,54]

    def __contains__(self, key):
        return key in self.numbers

Here you would get True when asking if 54 was in m:

>>> m = MyClass()
>>> 54 in m
True  

See documentation on overloading __contains__.




ANSWER 3

Score 3


Another way of having desired logic is to implement __iter__.

If you don't overload __contains__ python would use __iter__ (if it's overloaded) to check whether or not your data structure contains specified value.