Although comment stated that "merging keyword arguments for vector call is messy" (not exact quote), but I have found that it is fairly straight forward.

This achieves 2 goals:

1. Solves the raised issue ofpartial being stuck intp_call after keywords are deleted even if function supportsvectorcall.
2. Improves performance whenlen(pto-kw) != 0 and function supportsvectorcall.

Number 1. is solved better than it was in#119125 as there are no more switching between methods and fastervectorcall is used whenever appropriate. Also, this does not require additional variable in class struct.

Comparison of performance:

defsub(a,b):returna-bp=partial(sub,b=2)# Before%timeitp(1)# 240 ns# After%timeitp(1)# 180 ns# Using simpler but slower approach with `_PyObject_VectorcallDictTstate`%timeitp(1)# 200 ns

This is only initial attempt and I think the code can be made simpler. (much simpler if decide to use_PyObject_VectorcallDictTstate).

This will need to be adjusted to#119827 so do not merge.

• Issue:functools.partial does not re-set vector call. #119109