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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[1.20 regression] no longer accepts the empty tuple for `except ...:`","articleBody":"\u003c!--\nIf you're not sure whether what you're experiencing is a mypy bug, please see the \"Question and Help\" form instead.\nPlease consider:\n\n- checking our common issues page: https://mypy.readthedocs.io/en/stable/common_issues.html\n- searching our issue tracker: https://github.com/python/mypy/issues to see if it's already been reported\n- asking on gitter chat: https://gitter.im/python/typing\n--\u003e\n\n**Bug Report**\n\n\u003c!--\nIf you're reporting a problem with a specific library function, the typeshed tracker is better suited for this report: https://github.com/python/typeshed/issues\n\nIf the project you encountered the issue in is open source, please provide a link to the project.\n--\u003e\n\n`mypy` 1.20 no longer considers the empty tuple as a valid argument to `except ...:` unless it is explicitly annotated to be a (potentially empty) tuple of exception types. May be related to #17762 since the PR seems to be the last one that touched the exception-type-tuple handling for try-except block. \n\n(Same context as #21149: the [repo](https://gitlab.com/TTsangSC/pytest-autoprofile), the [failed pipeline](https://gitlab.com/TTsangSC/pytest-autoprofile/-/jobs/13742751853#L122), and the caveat about `mypy`-version behaviors [not lining up between `mypy` Playground and PyPI releases](https://github.com/python/mypy/issues/21149#user-content-fn-disclaimer-version-inconsistency-b9a62aedca4482d8cecd2b62fb6ffe81).)\n\n**To Reproduce**\n\n(Gist: https://gist.github.com/mypy-play/d0bd152e2e868b693ca73079096d13c6)\n\n```python\ndef this_no_longer_works() -\u003e None:\n    try:\n        pass\n    except ():\n        assert False, 'This should be unreachable'\n    \n\ndef but_this_still_does() -\u003e None:\n    accepted_errors: tuple[type[Exception], ...] = ()\n    try:\n        pass\n    except accepted_errors:\n        pass\n```\n\n(The real repo code of course doesn't just do a redundant `try: ... except: ...`, but uses it for e.g. [optional post-mortem debugging](https://gitlab.com/TTsangSC/pytest-autoprofile/-/blob/v0.19.1/.mock-ci/pytest_autoprofile_local_ci/cli.py?ref_type=tags#L368).)\n\n**Expected Behavior**\n\nType-check passes as with before\n\n**Actual Behavior**\n\n```log\nmain.py:4: error: Exception type must be derived from BaseException (or be a tuple of exception classes)  [misc]\nFound 1 error in 1 file (checked 1 source file)\n```\n\n**Your Environment**\n\n\u003c!-- Include as many relevant details about the environment you experienced the bug in --\u003e\n\n- Mypy version used: master (on Playground)\n- Mypy command-line flags: nil\n- Mypy configuration options from `mypy.ini` (and other config files): nil\n- Python version used: 3.14\n\n\u003c!-- You can freely edit this text, please remove all the lines you believe are unnecessary. --\u003e\n","author":{"url":"https://github.com/TTsangSC","@type":"Person","name":"TTsangSC"},"datePublished":"2026-04-02T22:59:12.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/21152/mypy/issues/21152"}