René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Sequence iterator thread-safety","articleBody":"# Bug report\r\n\r\n### Bug description:\r\n\r\nSequence iterators are not thread-safe under the free-threaded build. They'll sometimes be accessed with the same index.\r\n\r\nHere is a minimal repro:\r\n```python\r\nimport concurrent.futures\r\n\r\nN = 10000\r\n\r\nfor _ in range(100):\r\n    it = iter(range(N))\r\n\r\n    with concurrent.futures.ThreadPoolExecutor() as executor:\r\n        data = set(executor.map(lambda _: next(it), range(N)))\r\n\r\n    assert len(data) == N, f\"Expected {N} distinct elements, got {len(data)}\"\r\n```\r\n\r\nI also tested it with `list` and `dict` iterators as well as a custom class implementing `__getitem__`.\r\n\r\n\r\n### CPython versions tested on:\r\n\r\nCPython main branch\r\n\r\n### Operating systems tested on:\r\n\r\nLinux, macOS\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-120534\n* gh-120540\n* gh-120591\n* gh-120685\n* gh-120706\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/rostan-t","@type":"Person","name":"rostan-t"},"datePublished":"2024-06-14T12:01:02.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":10},"url":"https://github.com/120496/cpython/issues/120496"}