Difference between the in keyword and __contains__ in Python -


i wondering if 1 explain difference between "in" keyword of python , contains method

i working sample list , found behavior. when 2 supposed used? there efficiency can achieved if use 1 on other.

    >>> my_list = ["a", "b", "c"]     >>> my_list.__contains__("a")     true     >>> "a" in my_list     true

from docs:

for list , tuple types, x in y true if , if there exists index such x == y[i] true.

string types, x in y true if , if x substring of y. equivalent test y.find(x) != -1.

for user-defined classes define __contains__() method, x in y true if , if y.__contains__(x) true.

for user-defined classes not define __contains__() define __iter__(), x in y true if value z x == z produced while iterating on y. if exception raised during iteration, if in raised exception.

lastly, old-style iteration protocol tried: if class defines __getitem__(), x in y true if , if there non-negative integer index such x == y[i], , lower integer indices not raise indexerror exception.


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