[Python-Dev] Expected stability of PyCode_New() and types.CodeType() signatures
31.05.19 11:46, Petr Viktorin ????:
> PEP 570 (Positional-Only Parameters) changed the signatures of
> PyCode_New() and types.CodeType(), adding a new argument for "posargcount".
> Our policy for such changes seems to be fragmented tribal knowledge. I'm
> writing to check if my understanding is reasonable, so I can apply it
> and document it explicitly.
> There is a surprisingly large ecosystem of tools that create code objects.
> The expectation seems to be that these tools will need to be adapted for
> each minor version of Python.
I have a related proposition. Yesterday I have reported two bugs (and
Pablo quickly fixed them) related to handling positional-only arguments.
These bugs were occurred due to subtle changing the meaning of
co_argcount. When we make some existing parameters positional-only, we
do not add new arguments, but mark existing parameters. But co_argcount
now means the only number of positional-or-keyword parameters. Most code
which used co_argcount needs now to be changed to use
I propose to make co_argcount meaning the number of positional
parameters (i.e. positional-only + positional-or-keyword). This would
remove the need of changing the code that uses co_argcount.
As for the code object constructor, I propose to make posonlyargcount an
optional parameter (default 0) added after existing parameters.
PyCode_New() can be kept unchanged, but we can add new PyCode_New2() or
PyCode_NewEx() with different signature.