I have drafted a PEP (not officially submitted yet) to unify built-in and Python functions. Cython could benefit from this because cyfunctions could finally be considered functions without sacrificing performance. You find the proposal at https://github.com/jdemeyer/PEP-functions For comments and discussion, please post on the python-ideas thread https://mail.python.org/pipermail/python-ideas/2018-March/049563.html Happy Easter, Jeroen.