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pythonpython-2.7superpython-object

'super' object has no attribute '__eq__'

When I try to override the magic method __eq__, and use super to access the base method found in object, I get an error. There's no way this is a bug, but it sure feels like one:

class A(object):
    def __eq__(self, other):
        return super(A, self).__eq__(other)
A() == 0

# raises AttributeError: 'super' object has no attribute '__eq__'

This is unintuitive because object.__eq__ exists, but for class A(object): pass it doesn't. If I'm not mistaken __eq__ resorts to an is check, so that may be the workaround here, but using is instead of super isn't mixin friendly. Going that route is ok in my case, but in others it might not be.

Any suggestions, or info on why __eq__ works this way would be great.

Solution

  • As noted in Will's answer, object() does not actually implement __eq__ at all for instances (in python 2.7).

    You are being deceived by the fact that object.__eq__ exists into believing it must be a method that checks if instances of object are equal

    Instead, object.__eq__ is actually a class method, inherited from type, that is used to check if types are equal.

    That is, to handle expressions such as object == int and object == object.