bpo-37547: add _PyObject_CallMethodOneArg

[jdemeyer]

https://bugs.python.org/issue37547

[aeros]

In a similar theme to the proposed CallMethodOneArg() and existing CallNoArg(), CallOneArg(), and CallMethodNoArgs(), would it make sense to also have a VectorcallNoKws()? There's several instances where Vectorcall() is being used with a null value for the kwnames argument.

Edit: This would probably be in it's own separate PR and issue, not this one

[jdemeyer]

There's several instances where Vectorcall() is being used with a null value for the kwnames argument.

There are only very few such use cases. It we would add another function in similar spirit, I think that _PyObject_CallTwoArgs() would make the most sense and that was rejected.

[methane]

would it make sense to also have a VectorcallNoKws()?

No. Passing NULL is not so hard, compared to (PyObject*[]){self, arg}.

[aeros]

@jdemeyer @methane Thanks for the clarification.