mk, 06.11.2009 15:32:
>  Stefan Behnel wrote:
> >    class Test(object):
> >        def __eq__(self, other):
> >            return other == None
> >
> >    print Test() == None, Test() is None
>  
>  Err, I don't want to sound daft, but what is wrong in this example? It
>  should work as expected:
>  
>  >>> class Test(object):
>  ...     def __eq__(self, other):
>  ...         return other == None
>  ...
>  >>> Test() is None
>  False
>  >>> Test() == None
>  True

Yes, and it shows you that things can compare equal to None without being None.


>  Or perhaps your example was supposed to show that I should test for
>  identity with None, not for value with None?

Instead of "value" you mean "equality" here, I suppose. While there are
certain rare use cases where evaluating non-None objects as equal to None
makes sense, in normal use, you almost always want to know if a value is
exactly None, not just something that happens to return True when
calculating its equality to None, be it because of a programmer's concious
consideration or buggy implementation.

Stefan
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