I was recently playing around with decorators and experimenting with defining a function's signature dynamically at runtime, and came across the builtins.function class constructor (more easily accessible through the types.FunctionType alias). I quickly realized, however, that even though the constructor has a parameter (argdefs) that is used to specify default values for the resulting function's positional arguments, there is no corresponding parameter for keyword-only argument defaults. This seems like a glaring omission, especially considering the fact that argdefs takes a tuple that is directly assigned (unmodified) to the __defaults__ attribute. I can't find any obvious reason why there shouldn't be a similar "kwdefs" parameter that takes a dict and assigns it to __kwdefaults__. I downloaded the cpython repo, made this change myself as proof-of-concept, and compiled it, and it appears to work fine. This brings me to two questions:
1. Is there a reason for this disparity that I'm not seeing (e.g. breaking some other feature), or is it just an oversight?
2. If I wanted to submit this as an actual language change, would I need to write a full PEP or is it small enough that it could go to the issue tracker? (Note that the documentation says this constructor can vary between implementations, so the change would only apply to cpython if that matters.)
Also, if this is the wrong place to ask this, please feel free to set me straight; I'm completely new to this whole process, so any help on where to start would be appreciated.