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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"False positive `statement is unreachable` in try-finally related to KeyboardInterrupt","articleBody":"**Bug Report**\r\n\r\nA `KeyboardInterrupt` may interleave between the start of a `try` block and its contained statements. `mypy` seems to assume that the flow of execution will not be asynchronously interrupted.\r\n\r\n```python3\r\ndef fn() -\u003e None:\r\n    i: Optional[int] = None\r\n    try:\r\n        i = 1\r\n    finally:\r\n        if i is None:\r\n            return  # error: Statement is unreachable\r\n```\r\n\r\n**Expected Behavior**\r\n\r\nIt's trivial to show that this statement is reachable. Insert a `sleep` before the assignment:\r\n\r\n```python3\r\ndef fn() -\u003e None:\r\n    i: Optional[int] = None\r\n    try:\r\n        time.sleep(10)\r\n        i = 1\r\n    finally:\r\n        if i is None:\r\n            print(\"reachable\")\r\n            return\r\n```\r\n\r\nAnd then Ctrl+C (`KeyboardInterrupt`) the function during its execution. The `print` will run.\r\n\r\n**Your Environment**\r\n\r\n- Mypy version used: 0.960\r\n- Mypy command-line flags: `--warn-unreachable` seems to be the only flag necessary to reproduce this\r\n\r\n","author":{"url":"https://github.com/bbatliner","@type":"Person","name":"bbatliner"},"datePublished":"2022-07-11T18:41:57.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/13104/mypy/issues/13104"}