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 -- http://mail.python.org/mailman/listinfo/python-list
