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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Cannot call `issubclass()` against `typing.Protocol` on Python 3.12","articleBody":"# Bug report\r\n\r\nOn Python 3.11, you can do this:\r\n\r\n```pycon\r\n\u003e\u003e\u003e import typing\r\n\u003e\u003e\u003e issubclass(object, typing.Protocol)\r\nFalse\r\n```\r\n\r\nBut on Python 3.12 (following the backport of https://github.com/python/cpython/commit/c05c31db8c9dfd708b9857bb57f8e5f3ce40266d), this raises:\r\n\r\n```pycon\r\n\u003e\u003e\u003e import typing\r\n\u003e\u003e\u003e issubclass(object, typing.Protocol)\r\nTraceback (most recent call last):\r\n  File \"\u003cstdin\u003e\", line 1, in \u003cmodule\u003e\r\n  File \"C:\\Users\\alexw\\coding\\cpython\\Lib\\typing.py\", line 1797, in __subclasscheck__\r\n    raise TypeError(\r\nTypeError: Instance and class checks can only be used with @runtime_checkable protocols\r\n```\r\n\r\nThe new behaviour doesn't make sense. That `TypeError` should only be triggered if a user is calling `issubclass()` against a _subclass_ of `typing.Protocol`. `typing.Protocol` itself should be exempted.\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-105239\n* gh-105316\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/AlexWaygood","@type":"Person","name":"AlexWaygood"},"datePublished":"2023-06-02T12:48:09.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/105237/cpython/issues/105237"}