bpo-41559: Documentation for PEP 612 #24000
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Fidget-Spinner
requested review from
gvanrossum and
ilevkivskyi
as code owners
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@gvanrossum. Sorry, I did the reverse of what I'd initially promised - I was in a writing mood :). Really no hurry to review it though, we have a long way till 3.10 beta. This felt more difficult to write than what I did for PEP 585 and PEP 604 combined! Thinking of useful examples which were also understandable by users and copy-pastable/fully working as is wasn't easy. Maybe this is a sign that the typing module needs some refactoring work by the future Docs WG people. |
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Hmm I wonder if we should reorder the PEP-sized what's new items while we're at it. Strange that the current order is PEP 563, 613, 604, 612. |
| .. note:: | ||
| A ``GenericAlias`` object with :class:`typing.ParamSpec` parameters may not | ||
| have correct ``__parameters__`` after substitution because | ||
| :class:`typing.ParamSpec` is intended primarily for static type checking. |
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You don't need to add this to the note, but privately I'm interested in an example where it goes wrong?
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'''This example is from the typing module, though it will behave the same with the builtin GenericAlias'''
from typing import ParamSpec, TypeVar, Generic
P = ParamSpec('P')
T = TypeVar('T')
class X(Generic[P]): ...
# Empty tuple, because T is nested inside that list
print(X[int, str, T].__parameters__)
Co-Authored-By: Guido van Rossum <gvanrossum@users.noreply.github.com>
You're welcome! Unfortunately I have no clue how mypy works internally, so I don't think I'm the right person for that right now. |
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Thank you for taking the time to review this prosaic chunk of text. Getting this approved is an awesome way to start the new year! BTW, |
Please skip news, it shares the same news entry as GH-23702, thanks!
https://bugs.python.org/issue41559