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[spec] Document NotImplemented special casing? #2109

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[spec] Document NotImplemented special casing?#2109
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topic: typing specFor improving the typing spec

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@randolf-scholz
randolf-scholz
opened on Nov 2, 2025

Type checkers and typeshed special case NotImplemented to be treated as Any, this appears to be not documented in the spec currently.

A small paragraph should probably go here: https://typing.python.org/en/latest/spec/special-types.html

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  1. randolf-scholz
    added
    topic: documentationDocumentation-related issues and PRs
    on Nov 2, 2025
  2. srittau
    added
    topic: typing specFor improving the typing spec
    and removed
    topic: documentationDocumentation-related issues and PRs
    on Nov 2, 2025

  3. tyralla commented on Nov 7, 2025

    @tyralla
    tyralla
    on Nov 7, 2025

    I am not aware of a case where treating NotImplemented as Any is really useful, and recently opened python/mypy#20114 to remove this special casing from Mypy. An idea is to use NotImplemented / NotImplementedType to specify the behaviour of binary operators as discussed in #1548.

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