there's a bug in the copy function that i wanted to fix: def copy(obj): cls, state = obj.__getstate__() return cls.__setstate__(state) also, but there's a reason why __getstate__ returns "(cls, state)" rather than just "state", and that's to keep things agile. i don't want to be necessarily tightly-coupled to a certain type. the cls will be used to reconstruct the object (cls.__setstate__), much like the function returned by __reduce__, so normally, __getstate__ would just return self.__class__ for cls. but there are times, especially when object proxies are involved, that we may want to "lie" about the actual type, i.e., use a different type to reconstruct the object with. here's an example that shows why: class ListProxy: ... def __getstate__(self): return list, self._value instances of ListProxy, when stored in a file (i.e., shelf), want to be pickled by value. moreover, when they are loaded from a file, they want to loaded as actual lists, not proxies, as the proxied object is long lost. so returning a tuple of (cls, state) gives more freedom to frameworks and other utilities. of course, again, most code would just return (self.__class__, state) -tomer