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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Output type of warnings.catch_warnings with record=True","articleBody":"Although [warnings.catch_warnings](https://docs.python.org/3/library/warnings.html#warnings.catch_warnings) with `record=True` returns\r\na list, mypy is not aware of that:\r\n\r\nFile `foo.py`:\r\n\r\n```python\r\nimport warnings\r\n\r\nwith warnings.catch_warnings(record=True) as w:\r\n    print(len(w))\r\n```\r\n\r\nCommand `mypy foo.py` gives:\r\n\r\n```\r\n$ mypy foo.py\r\nfoo.py:4: error: Argument 1 to \"len\" has incompatible type \"Optional[List[_Record]]\"; expected \"Sized\"\r\nFound 1 error in 1 file (checked 1 source file)\r\n```\r\n\r\nUsing recent mypy from master (`0.750+dev.e97377c454a1d5c019e9c56871d5f229db6b47b2`).\r\n\r\n---\r\n\r\nI've attached PR fixing this #3464.","author":{"url":"https://github.com/mslapek","@type":"Person","name":"mslapek"},"datePublished":"2019-11-14T07:11:54.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/3463/typeshed/issues/3463"}