How does a Python set([]) check if two objects are equal? What methods does an object need to define to customise this?
Yes, you need a __hash__()-method AND the comparing-operator which you already provided.
class Item(object): def __init__(self, foo, bar): self.foo = foo self.bar = bar def __repr__(self): return "Item(%s, %s)" % (self.foo, self.bar) def __eq__(self, other): if isinstance(other, Item): return ((self.foo == other.foo) and (self.bar == other.bar)) else: return False def __ne__(self, other): return (not self.__eq__(other)) def __hash__(self): return hash(self.__repr__())
I am afraid you will have to provide a __hash__() method. But you can code it the way, that it does not depend on the mutable attributes of your Item.