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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"PEP 695 syntax doesn't work for generic NamedTuples","articleBody":"Since Python 3.11, defining generic `NamedTuple`s has been legal, like so:\r\n\r\n```pycon\r\n\u003e\u003e\u003e from typing import *\r\n\u003e\u003e\u003e T = TypeVar(\"T\")\r\n\u003e\u003e\u003e class Foo(NamedTuple, Generic[T]):\r\n...     x: T\r\n\u003e\u003e\u003e\r\n```\r\n\r\nHowever, using the new PEP-695 syntax for generic `NamedTuple`s fails with a slightly inexplicable error message:\r\n\r\n```pycon\r\n\u003e\u003e\u003e from typing import *\r\n\u003e\u003e\u003e class Foo[T](NamedTuple):\r\n...     x: T\r\n...\r\nTraceback (most recent call last):\r\n  File \"\u003cstdin\u003e\", line 1, in \u003cmodule\u003e\r\n  File \"\u003cstdin\u003e\", line 1, in \u003cgeneric parameters of Foo\u003e\r\n  File \"C:\\Users\\alexw\\coding\\cpython\\Lib\\typing.py\", line 2707, in __new__\r\n    setattr(nm_tpl, key, ns[key])\r\nAttributeError: attribute '__type_params__' of 'type' objects is not writable\r\n```\r\n\r\nUsing PEP-695 syntax for generic `TypedDict`s seems to work fine, but isn't tested anywhere in `test_typing.py`, as far as I can tell:\r\n\r\n```pycon\r\n\u003e\u003e\u003e class Bar[T](TypedDict):\r\n...     x: T\r\n...\r\n\u003e\u003e\u003e Bar.__type_params__\r\n(T,)\r\n\u003e\u003e\u003e Bar.__orig_bases__\r\n(\u003cfunction TypedDict at 0x0000017E9A17D9D0\u003e, typing.Generic[T])\r\n\u003e\u003e\u003e Bar.__mro__\r\n(\u003cclass '__main__.Bar'\u003e, \u003cclass 'typing.Generic'\u003e, \u003cclass 'dict'\u003e, \u003cclass 'object'\u003e)\r\n```\r\n\r\nCc. @JelleZijlstra","author":{"url":"https://github.com/AlexWaygood","@type":"Person","name":"AlexWaygood"},"datePublished":"2023-05-18T16:20:14.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/104616/cpython/issues/104616"}