Your __cmp__ method will always return 0, so all objects will be equal when you add the method, as Simon and Steve pointed out. The result is all objects will pass the test of being a member of excluded. If you do not add a __cmp__ method objects will be compared on identy - call the id() function to see the identity of an object. An alternative would be Steve's proposal to compare on the id attribute instead of the allocated attribute
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