3.3.5. Emulating container types object.__reversed__(self) says in 3.0 and 3.1 and I assume in 2.x: "Objects should normally only provide __reversed__() if they do not support the sequence protocol and an efficient implementation of reverse iteration is possible." The builtin sequences violate this because because they do support the sequence and have __ reversed__ methods anyway. And iterables that do not support that protocol obviously *must* provide a method to be reverse iterable. I believe the point is that it is hard for Python code to beat the C-coded version of the obvious def __reversed__(self): for i in reversed(range(self.__len__)): yield self.__getitem__(i) So I think the entry should say: "Objects that support the sequence protocol should only provide __reversed__ if they can provide an implementation that is more efficient than the one provided by reversed()." possibly followed by "Objects that do not supposrt the sequence protocol must provide __reversed__ to be reverse iterable."

Thanks, fixed in r72675.