Move getmethparlist function from turtle to inspect module

[adorilson]

Feature or enhancement

Proposal:

The getmethpartlist turtle module function does work which seems to be supposed to be done by the inspect module.

In fact, getmethpartlist calls inspect.signature and then iterates over it to produce a call to the callable. Perhaps this second part could also be implemented in the inspect module.

In an issue, @terryjreedy said, “For calls that just want the call signature, I wonder if calling getmethodparlist could be replaced by calling signature.”

So, my suggestion is to add two new methods to Signature class, which:

1. Returns the call:

class Signature():
    def as_call(self) -> string : ...

2. Returns a new Signature without the first parameter if ob is a method:

class Signature():
    def as_function(self): ...

Then, getmethpartlist could be:

def getmethpartlist(ob):
    defs = inspect.signature(ob).as_function()
    call = defs.as_call()
   return str(defs), call

Thoughts?

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

https://discuss.python.org/t/move-getmethparlist-function-from-turtle-to-inspect-module/97172

[serhiy-storchaka]

turtle.getmethparlist() is an internal function. It is so specific, that I doubt it would be useful anywhere else.

The first part is getting signature for a method from a function that implements the method. I.e. get rid of the "self" parameter. It uses a kind of hack:

orig_sig = inspect.signature(ob)
func_sig = orig_sig.replace(parameters=list(orig_sig.parameters.values())[1:])

It could be written in different ways:

func_sig = inspect.signature(functools.partial(ob, None))

or

func_sig = inspect.signature(ob.__get__(object()))

I had a plan for adding the Signature.partial() method which would allow to get a signature of partial function from a signature of function:

signature(callable).partial(*args, **kwargs) == signature(partial(callable, *args, **kwargs))

but I'm not sure how useful such a feature would be. At least for turtle there are other ways.

The second part of turtle.getmethparlist() is specific to turtle. It is only useful in the specific case of code generation. It does not work if you need to omit some arguments, pass additional arguments or pass other values as arguments.

[adorilson]

turtle.getmethparlist() is an internal function. It is so specific, that I doubt it would be useful anywhere else.

I had a slight doubt about this too.

I didn't find any other case in stdlib with this code pattern in the second part of turtle.getmethpartlist(), and I don't know another stdlib module with both interface (OO and module namespace), like turtle. But other people would know.

However, there are some cases outside stdlib: matplotlib.pyplot, PIL.Image, pygame, seaborn. I couldn't check deeply how its do this, but maybe they can benefit from a method like this.

These are the reasons I thought this could be a nice new enhancement, eventually.

Update: I found the multiprocessing stdlib module has a Context default object and exposes its methods via the module namespace. But does this in a way completely different from turtle.