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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"asyncio blocks custom BaseException exceptions","articleBody":"# Bug report\n\n### Checklist\n\n- [X] I am confident this is a bug in CPython, not a bug in a third-party project\n- [X] I have searched the [CPython issue tracker](https://github.com/python/cpython/issues?q=is%3Aissue+sort%3Acreated-desc),\nand am confident this bug has not been reported before\n\n\n### CPython versions tested on:\n\n3.11\n\n### Operating systems tested on:\n\nLinux\n\n### Output from running 'python -VV' on the command line:\n\nPython 3.11.4 (main, Jun  7 2023, 00:00:00) [GCC 13.1.1 20230511 (Red Hat 13.1.1-2)]\n\n### A clear and concise description of the bug:\n\nSince bpo-32528, this code no longer works:\n\n```python\nimport asyncio\n\nclass ShowStopper(BaseException):\n    pass\n\ndef hello_world(loop):\n    print('Hello World')\n    raise ShowStopper(\"Stop\")\n\nloop = asyncio.get_event_loop()\n\nloop.call_soon(hello_world, loop)\n\nloop.run_forever()\nloop.close()\n```\n\nI think this behaviour is very surprising as the general behaviour of exceptions based on `BaseException` is that they propagate over error handling. Currently, we'd need to do something hacky like inherit from `SystemExit` instead, basically relegating `BaseException` to something internal.\n\nThis issue was mentioned in the PR, and supposed to be adjusted for Python 3.9:\n\nhttps://github.com/python/cpython/pull/13528#pullrequestreview-241938649\n\nUnfortunately, it seems that was forgotten.","author":{"url":"https://github.com/CendioOssman","@type":"Person","name":"CendioOssman"},"datePublished":"2023-08-31T08:21:45.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/108711/cpython/issues/108711"}