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gh-138859: Account forParamSpec defaults that are not lists …#138868
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python-cla-botbot commentedSep 13, 2025 • edited
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All commit authors signed the Contributor License Agreement. |
Most changes to Pythonrequire a NEWS entry. Add one using theblurb_it web app or theblurb command-line tool. If this change has little impact on Python users, wait for a maintainer to apply the |
Lib/typing.py Outdated
| elifisinstance(args[i],list): | ||
| args= (*args[:i],tuple(args[i]),*args[i+1:]) | ||
| else: | ||
| args= (*args[:i],args[i],*args[i+1:]) |
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this can be simplified toargs = tuple(args)
| @@ -0,0 +1 @@ | |||
| Fix failure during parameterization of generics when a non-type-list `ParamSpec` default is followed by another type variable default, and the `ParamSpec` is not provided as a type argument. | |||
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We userst, notmd in NEWS, so please use double backticks.
Lib/typing.py Outdated
| # Convert lists to tuples to help other libraries cache the results. | ||
| elifisinstance(args[i],list): | ||
| args= (*args[:i],tuple(args[i]),*args[i+1:]) | ||
| else: |
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Should we create a tuple directly on line 1103 above instead?
| @@ -0,0 +1 @@ | |||
| Fix failure during parameterization of generics when a non-type-list ``ParamSpec`` default is followed by another type variable default, and the ``ParamSpec`` is not provided as a type argument. | |||
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Sorry, I don't understand what "non-type-list" is. I propose this wording:
| Fix failure during parameterization of generics when a non-type-list ``ParamSpec`` default is followed by another type variable default, and the ``ParamSpec`` is not provided as a type argument. | |
| Fixes a:exc:`TypeError` when substituting a:class:`ParamSpec` with a default | |
| that is followed by another:class:`TypeVar` with a default. |
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Thanks, the original description was unclear. Unless there are other objections, I'll reduce it to
Fix generic type parameterization raising a :exc:
TypeErrorwhen omitting a :class:ParamSpecthat has a non-type-list default.
"Non-type-list default" refers to the bug occurring if the ParamSpec default isn't a list of types, such as... orP (another ParamSpec in scope). The bug would not be encountered if the default was a list of types (like[int, str]).
I think the closest wording for this construct in the documentation is actually "list of types" (see e.g.ParamSpec Defaults), but I don't think "list of types" is necessarily better than "type list".
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Let's say something like "default that is not a list of types". "type list" is definitely less clear to me than "list of types".
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Rewording suggestions done in9669479
@bzoracler Something left to do here? Is it ready for review? |
@sergey-miryanov I think I've addressed everything. @JelleZijlstra Are there any other concerns? |
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Thanks@bzoracler for the PR, and@JelleZijlstra for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14. |
pythonGH-138868)(cherry picked from commit379fd02)Co-authored-by: bzoracler <50305397+bzoracler@users.noreply.github.com>
pythonGH-138868)(cherry picked from commit379fd02)Co-authored-by: bzoracler <50305397+bzoracler@users.noreply.github.com>
GH-140207 is a backport of this pull request to the3.14 branch. |
GH-140208 is a backport of this pull request to the3.13 branch. |
@bzoracler it looks like you'll have to re-sign the CLA under a different email address for the backports (#140208 and#140207) to go through. As I understand it this can happen if you have different email addresses associated with your GitHub account and your commits. |
@JelleZijlstra oh, it looks like rebasing straight from the GitHub UI made the commits under a different email address ( Thanks all! |
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…when converting type argument list to tuple
Allows omitting common
ParamSpecdefaults, like...or anotherParamSpec.ParamSpec(default=...)fails if not provided as a type argument and not in the last position of a type list when passing type arguments #138859ParamSpec(default=...)fails if not provided as a type argument and not in the last position of a type list when passing type arguments #138859