Hello, Just a quick note that I have a working PEP 3151 implementation at http://hg.python.org/features/pep-3151/, in named branch "pep-3151". The implementation is (should be) complete on the feature side, so you can play with it right now. It still lacks a deprecation mechanism for old names. It is tracked in http://bugs.python.org/issue12555. Regards Antoine.