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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Inverted enum.Flag","articleBody":"# Bug report\r\n\r\n## Checklist\r\n- [X] I am confident this is a bug in CPython, not a bug in a third-party project\r\n- [X] I have searched the CPython issue tracker, and am confident this bug has not been reported before\r\n\r\n## A clear and concise description of the bug\r\nAdding **inverted** option to enum.Flag brakes  logic of enum. \r\nI assume it caused by ambiguous implementation of `bitwise NOT` in Flag which processes ~value option different inside class scope and outside class scope unlike `bitwise OR`\r\n\r\n  ```py\r\nimport enum\r\n\r\nclass X(enum.Flag):\r\n    a = enum.auto()\r\n    b = enum.auto()\r\n    c = a | b\r\n\r\n\r\nassert list(X) == [X.a, X.b]\r\nassert ~X.a == X.b\r\nassert list(~X.a) == [X.b]\r\n\r\n\r\nclass Y(enum.Flag):\r\n    a = enum.auto()\r\n    b = enum.auto()\r\n    c = a | b\r\n    d = ~a  # this line brakes the code\r\n\r\n\r\nassert list(Y) == [Y.a, Y.b]\r\nassert ~Y.a == Y.b  # AssertionError\r\nassert list(~Y.a) == [Y.b]  # ValueError: -2 is not a positive integer\r\n  ```\r\nTraceback:\r\n  ``` bash\r\nTraceback (most recent call last):\r\n  File \"\u003cstdin\u003e\", line 1, in \u003cmodule\u003e\r\n  File \"/opt/homebrew/Cellar/python@3.11/3.11.4_1/Frameworks/Python.framework/Versions/3.11/lib/python3.11/enum.py\", line 1482, in __iter__\r\n    yield from self._iter_member_(self._value_)\r\n  File \"/opt/homebrew/Cellar/python@3.11/3.11.4_1/Frameworks/Python.framework/Versions/3.11/lib/python3.11/enum.py\", line 1359, in _iter_member_by_value_\r\n    for val in _iter_bits_lsb(value \u0026 cls._flag_mask_):\r\n  File \"/opt/homebrew/Cellar/python@3.11/3.11.4_1/Frameworks/Python.framework/Versions/3.11/lib/python3.11/enum.py\", line 122, in _iter_bits_lsb\r\n    raise ValueError('%r is not a positive integer' % original)\r\nValueError: -2 is not a positive integer\r\n```\r\n# Your environment\r\n- CPython versions tested on: Clang 14.0.3 (clang-1403.0.22.14.1)\r\n- Operating system and architecture: 22.5.0 Darwin Kernel Version 22.5.0: Thu Jun  8 22:22:20 PDT 2023; root:xnu-8796.121.3~7/RELEASE_ARM64_T6000 arm64\r\n\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-132273\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/GrafLearnt","@type":"Person","name":"GrafLearnt"},"datePublished":"2023-08-01T13:54:59.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":10},"url":"https://github.com/107538/cpython/issues/107538"}