[New-bugs-announce] [issue29318] Optimize _PyFunction_FastCallDict() for **kwargs

STINNER Victor report at bugs.python.org
Thu Jan 19 06:33:01 EST 2017

New submission from STINNER Victor:

def func(x, y):
    print(x, y)

def proxy2(func, **kw):

def proxy1(func, **kw):
    proxy2(func, **kw)

The "proxy2(func, **kw)" call in proxy1() is currently inefficient: _PyFunction_FastCallDict() converts the dictionary into a C array [key1, value1, key2, value2, ...] and then _PyEval_EvalCodeWithName() rebuilds the dictionary from the C array.

Since "func(*args, **kw)" proxies are common in Python, especially to call the parent constructor when overriding __init__, I think that it would be interesting to optimize this code path.

I first expected that it was a regression of FASTCALL, but Python < 3.6 doesn't optimize this code neither.

components: Interpreter Core
messages: 285773
nosy: haypo, inada.naoki
priority: normal
severity: normal
status: open
title: Optimize _PyFunction_FastCallDict() for **kwargs
type: performance
versions: Python 3.7

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