functools.partial should use PEP612 ParamSpec (depends on #8708)
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Description
Currently, functools.partial's __call__ method takes *args: Any, **kwargs: Any and returns _T (a TypeVar for the return type of the callable the partial is wrapping). This is decent, but matching the parameter typing would make this more useful in more situations.
I can sort of see how to deal with this, although I'll admit I'm unsure how to make this generically work. I imagine you could probably deal with some number of Concatenates (maybe up to 5 or 10) to deal with most cases. It's possible fixing this requires another PEP to allow an arbitrary-length Concatenate-type pattern.
Related to https://github.com/python/mypy/issues/1484
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with stdlib/functools.pyi around line 75 and review PEP 612's ParamSpec and Concatenate concepts. Check the dependency on issue #8708 and the related mypy issue before deciding whether the requested typing is expressible. Done means functools.partial's call preserves the wrapped callable's parameter typing rather than using Any.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- tooling
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 25/100