Starting in Python 3.2, range() supports fast containment checking for integers (i.e. based on an O(1) arithmetic calculation rather than an O(N) iteration through the entire sequence). Currently, this fast path ignores objects that implement __index__ - they are relegated to the slow iterative search. This seems wrong to me - the semantics of __index__ are such that it is meant to be used for objects that are alternative representations of the corresponding Python integers (e.g. numpy scalars, or integers that use a particular number of bits in memory). Under that interpretation, if an object provides __index__, we should use the fast path instead of calling __eq__ multiple times. Thoughts? Regards, Nick. -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia