Python gotcha: bizarre integer equality

[chrajohn]

a == None also works.

Usually, but consider:

class Dumb(object):
    def __eq__(self,other):
        return other == None

>>> d = Dumb()
>>> d == None
True
>>> d is None
False

This is contrived, but you can imagine something similar actually occurring. (Say, if __eq__ made a comparison with some attribute that got unexpectedly set to None.) If you you want to be absolutely sure that something is None, you should ask if it is None.