[New-bugs-announce] [issue45295] _PyObject_GetMethod/LOAD_METHOD for C classmethods

Ken Jin report at bugs.python.org
Sun Sep 26 12:29:41 EDT 2021

New submission from Ken Jin <kenjin4096 at gmail.com>:

LOAD_METHOD + CALL_METHOD currently doesn't work for Python @classmethod and C classmethod (METH_CLASS). They still create bound classmethods which are fairly expensive.

I propose supporting classmethods. I have an implementation for C classmethods. It passes most of the test suite, and I've also got it to play along with PEP 659 specialization.

Some numbers from Windows release build (PGO build will likely be less favorable):

python.exe -m timeit "int.from_bytes(b'')"
2000000 loops, best of 5: 107 nsec per loop
5000000 loops, best of 5: 72.4 nsec per loop

Funnily enough, `(1).from_bytes()` still needs a bound classmethod, but I think people usually use the other form.

A toy PR will be up for review. I will then split the change into two parts (one for _PyObject_GetMethod changes, another for PEP 659 specialization) to help decide if the maintenance-perf ratio is worth it.

components: Interpreter Core
messages: 402668
nosy: kj
priority: normal
severity: normal
status: open
title: _PyObject_GetMethod/LOAD_METHOD for C classmethods
type: performance
versions: Python 3.11

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