René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Many functions that accept Iterable should actually accept Iterable | SupportsGetItem","articleBody":"Many functions in stdlib that are documented to accept an \"iterable\" are annotated as `Iterable[T]`. This means the arguments must have `__iter__`. However, the actual functions don't require the arguments to have `__iter__`, they also work with arguments that have only `__getitem__`. That's because internally they use `iter` (in Python) or [PySequence_Fast](https://docs.python.org/3/c-api/sequence.html#c.PySequence_Fast) (in C).\r\n\r\nAs the docs for both `iter` and `PySequence_Fast` functions show, these functions support two protocols for the argument: the \"iterable\" protocol (`__iter__`) and the \"sequence\" protocol (`__getitem__`).\r\n\r\nExample functions that have this bug right now:\r\n```\r\nenumerate\r\niter\r\nstr.join\r\nbytes.__new__\r\nbytes.join\r\n```\r\n\r\nFor enumerate, a bug was actually filed [on the mypy repo](https://github.com/python/mypy/issues/9737) but in fact I believe this should be corrected in typeshed.\r\n\r\nAside: `for` loops also similarly accept \"iterables\" that have only `__getitem__`, but that is implemented inside type checkers themselves. For now mypy [still doesn't](https://github.com/python/mypy/issues/11695) support it properly, but Pyright does.\r\n","author":{"url":"https://github.com/matangover","@type":"Person","name":"matangover"},"datePublished":"2022-05-09T21:32:37.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":28},"url":"https://github.com/7813/typeshed/issues/7813"}