[Python-Dev] PEP 575 (Unifying function/method classes) update

Jeroen Demeyer J.Demeyer at UGent.be
Sat May 5 04:55:02 EDT 2018

Hello all,

I have updated PEP 575 in response to some posts on this mailing list 
and to some discussions in person with the core Cython developers.
See https://www.python.org/dev/peps/pep-0575/

The main differences with respect to the previous version are:

* "builtin_function" was renamed to "cfunction". Since we are changing 
the name anyway, "cfunction" looked like a better choice because the 
word "built-in" typically refers to things from the builtins module.

* defined_function now only defines an API (it must support all 
attributes that a Python function has) without specifying the 

* The "Two-phase Implementation" proposal for better backwards 
compatibility has been expanded and now offers 100% backwards 
compatibility for the classes and for the inspect functions.


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