Hi, the short version of my question is: when is a dictionary's __contains__ method behavior different to using the 'in' idiom? (because I have an example of a difference in my code).
Longer version: I have a user-defined class with a few overrides of special methods, particularly __eq__ and __ne__. I also have a dictionary keyed by instances of these classes, and I'm confused about the unexpected behavior trying to test whether an instance is in the dictionary's keys. The instance is i and the dictionary is d. I have been using the idiom i in d which I understood to be the pythonic way to test the keys, but it doesn't work. However, when I debug my code I see the instance in the list of keys, and in fact i in d.keys() and d.keys()[10] == i both return True. But d.__contains__(i) d.has_key(i) d.keys()[10] is i return False. I put a print statement in my class's __eq__ method and it is being called. It tests equality of some of my class instance's attributes. I didn't realize there was any situation where you could expect different results from i in d versus i in d.keys() -- am I misunderstanding something? I'm not sure what other details to provide! Thanks a lot, Rob -- http://mail.python.org/mailman/listinfo/python-list
