Hi, I am currently at a CPython sprint 2017 at Facebook. We are discussing my idea of writing a new C API for CPython hiding implementation details and replacing macros with function calls. I wrote a short blog post to explain the issue of the current API, the link between the API and the ABI, and give examples of optimizations which become possible with an "unsable" stable ABI: https://haypo.github.io/new-python-c-api.html I am sorry, I'm too busy to write a proper PEP. But here is the link to my old PEP draft written in June. I didn't update it yet. But multiple people are asking me for the PEP draft, so here you have! https://github.com/haypo/misc/blob/master/python/pep_c_api.rst See also the thread on python-ideas last June, where I first proposed my draft: [Python-ideas] PEP: Hide implementation details in the C API https://mail.python.org/pipermail/python-ideas/2017-July/046399.html This is not a request for comments :-) I will write a proper PEP for that. Victor