gh-117516: Implement typing.TypeIs #117517
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carljm
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Apr 3, 2024
Doc/library/typing.rst
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| ``TypeGuard`` also works with type variables. See :pep:`647` for more details. | ||
| ``TypeIs`` also works with type variables. For more information, see | ||
| PEP 742 (Narrowing types with ``TypeIs``). |
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Same question here as below -- should we link to typing spec instead of PEP?
If we do link to PEP, should probably make it a real link using :pep: role
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Adding the link for now, we should figure out how to set up intersphinx to enable linking to the spec.
carljm
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Apr 5, 2024
Doc/library/typing.rst
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| are incompatible (e.g., ``list[object]`` to ``list[int]``) and when the | ||
| function does not return ``True`` for all instances of the narrowed type. | ||
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| Using ``-> TypeIs`` tells the static type checker that for a given |
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Would it be clearer to use TypeIs[...] or TypeIs[SomeType] here? The latter would also give you a name that might be clearer/shorter than "the type inside TypeIs" below.
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Good idea, done. Also changed the docstrings of TypeGuard and TypeIs accordingly.
Co-authored-by: Carl Meyer <carl@oddbird.net>
picnixz
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Apr 6, 2024
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
diegorusso
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Apr 17, 2024
See PEP 742. Co-authored-by: Carl Meyer <carl@oddbird.net> Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
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This adds
typing.TypeIs, as proposed in PEP-742.The runtime implementation is trivial but the documentation is important here. As suggested in the PEP (https://peps.python.org/pep-0742/#how-to-teach-this), I made the documentation emphasize TypeIs over TypeGuard, and the TypeGuard docs now focus on how it is different from TypeIs.
📚 Documentation preview 📚: https://cpython-previews--117517.org.readthedocs.build/