Proposed patch makes _PyArg_NoKeywords(), _PyArg_NoStackKeywords() and _PyArg_NoPositional() macros. This eliminates the overhead of the cross-module function call in common case.

This idea was previously discussed in issue26822 and raised again in issue29452.

+1

New changeset 82d1c8d15e18 by Serhiy Storchaka in branch 'default':
Issue #29460: _PyArg_NoKeywords(), _PyArg_NoStackKeywords() and
https://hg.python.org/cpython/rev/82d1c8d15e18

Oh right, I recall that I proposed it. Thanks for this change :-)

The next question might it: would it be worth it to try using unlikely() macro on (kwargs == NULL) test in the macro? ;-)

I'm talking about GCC/Clang __builtin_expect:

#define unlikely(x)     __builtin_expect((x),0)

New changeset f5ef851ff6b26529382747cfea4674158c7c1ebc by Serhiy Storchaka in branch 'master':
Issue #29460: _PyArg_NoKeywords(), _PyArg_NoStackKeywords() and
https://github.com/python/cpython/commit/f5ef851ff6b26529382747cfea4674158c7c1ebc

> The next question might it: would it be worth it to try using unlikely()
> macro on (kwargs == NULL) test in the macro? ;-)

Perhaps this may help in some critical tight loops (in implementations of 
dict, string operations or long integer arithmetic), but I doubt it can have 
any measurable effect when used once per a call of a function calling 
PyArg_Parse* and using many other stuff.

I created the issue #29461: "Experiment usage of likely/unlikely in CPython core".