[Python-Dev] Comparing PEP 576 and PEP 580

Petr Viktorin encukou at gmail.com
Fri Jul 6 14:33:26 EDT 2018

On 07/05/18 13:59, Jeroen Demeyer wrote:
> On 2018-07-05 13:32, INADA Naoki wrote:
>> Core devs interested in this area is limited resource.
> I know and unfortunately there is nothing that I can do about that. It 
> would be a pity that PEP 580 (or a variant like PEP 576) is not accepted 
> simply because no core developer cares enough.

I do care about this, and I'm really sorry I've been mostly silent here.
Unfortunately, this is the kind of work that can't be done with a few 
hours in the evenings, and currently an urgent project is sucking up all 
the big blocks of time I have :(
That project should be done in a month or two, however.

>> As far as I understand, there are some important topics to discuss.
>> a. Low level calling convention, including argument parsing API.
>> b. New API for calling objects without argument tuple and dict.
>> c. How more types can support FASTCALL, LOAD_METHOD and CALL_METHOD.
>> d. How to reorganize existing builtin types, without breaking stable ABI.
> Right, that's why I wanted PEP 580 to be only about (c) and nothing 
> else. I made the mistake in PEP 575 of also involving (d).
> I still don't understand why we must finish (a) before we can even start 
> discussing (c).
>> Reference implementation helps discussion.
> METH_FASTCALL and argument parsing for METH_FASTCALL is already 
> implemented in CPython. Not in documented public functions, but the 
> implementation exists.
> And PEP 580 also has a reference implementation:
> https://github.com/jdemeyer/cpython/tree/pep580
> Jeroen.
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