Op 2004-12-18, Roy Smith schreef <[EMAIL PROTECTED]>: > Nick Coghlan <[EMAIL PROTECTED]> wrote: > [quoting from the Reference Manual] >> If a class defines mutable objects and implements a __cmp__() >> or __eq__() method, it should not implement __hash__(), since the dictionary >> implementation requires that a key's hash value is immutable (if the >> object's >> hash value changes, it will be in the wrong hash bucket)." > > I know that's what it says, but I don't think it's good advice. All > that is really required is that __hash__() always returns the same value > over the lifetime of the object, and that objects which __cmp__() the > same always return the same hash value. That's it. That's all a > dictionary cares about.
It cares about even less. It only cares that these conditions are met while the object is a key. If those things would change before or after the object is a key, the dictionary wouldn't care about it. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
