René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"3.11.4: ValueError when inverting enum.Flag member with mask member","articleBody":"With code such as:\r\n\r\n```python\r\nimport enum\r\n\r\nclass Flag(enum.Flag):\r\n    A = 0x01\r\n    B = 0x02\r\n    Mask = 0xff\r\n\r\nprint(~Flag.A)\r\n```\r\n\r\nPython 3.10.11 prints `Flag.B`, and so does Python 3.11.3. However, with Python 3.11.4, this happens instead:\r\n\r\n```pytb\r\nTraceback (most recent call last):\r\n  File \"/home/florian/tmp/f.py\", line 9, in \u003cmodule\u003e\r\n    print(~Flag.A)\r\n          ^^^^^^^\r\n  File \"/usr/lib/python3.11/enum.py\", line 1542, in __invert__\r\n    self._inverted_ = self.__class__(self._flag_mask_ ^ self._value_)\r\n                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\r\n  File \"/usr/lib/python3.11/enum.py\", line 711, in __call__\r\n    return cls.__new__(cls, value)\r\n           ^^^^^^^^^^^^^^^^^^^^^^^\r\n  File \"/usr/lib/python3.11/enum.py\", line 1136, in __new__\r\n    raise exc\r\n  File \"/usr/lib/python3.11/enum.py\", line 1113, in __new__\r\n    result = cls._missing_(value)\r\n             ^^^^^^^^^^^^^^^^^^^^\r\n  File \"/usr/lib/python3.11/enum.py\", line 1454, in _missing_\r\n    raise ValueError('%r: no members with value %r' % (cls, unknown))\r\nValueError: \u003cflag 'Flag'\u003e: no members with value 252\r\n```\r\n\r\nAs a workaround, a detour via `.value` works in this case:\r\n\r\n```python\r\n\u003e\u003e\u003e Flag((Flag.A | Flag.B).value \u0026 ~Flag.A.value)\r\n\u003cFlag.B: 2\u003e\r\n```\r\n\r\nThis causes issues with PyQt, which has the following flags ([as bindings from C++](https://github.com/qt/qtbase/blob/v6.5.1/src/corelib/global/qnamespace.h#L1047-L1057)):\r\n\r\n```python\r\n\u003e\u003e\u003e from PyQt6.QtCore import Qt\r\n\u003e\u003e\u003e for e in Qt.KeyboardModifier:\r\n...     print(f\"{e.name} = {hex(e.value)}\")\r\n... \r\nNoModifier = 0x0\r\nShiftModifier = 0x2000000\r\nControlModifier = 0x4000000\r\nAltModifier = 0x8000000\r\nMetaModifier = 0x10000000\r\nKeypadModifier = 0x20000000\r\nGroupSwitchModifier = 0x40000000\r\nKeyboardModifierMask = 0xfe000000\r\n```\r\n\r\n(Output from Python 3.10 - with Python 3.11, `KeyboardModifierMask` goes missing in the output, and so does `Flag.Mask` above, but that seems like a different issue?)\r\n\r\nWith my project, I'm [trying to remove a modifier](https://github.com/qutebrowser/qutebrowser/issues/7735) from the given flags. With Python 3.10.11 and 3.11.3:\r\n\r\n```python\r\n\u003e\u003e\u003e (Qt.KeyboardModifier.ShiftModifier | Qt.KeyboardModifier.ControlModifier) \u0026 ~Qt.KeyboardModifier.ControlModifier\r\n\u003cKeyboardModifier.ShiftModifier: 33554432\u003e\r\n```\r\n\r\nBut with Python 3.11.4, same issue as above:\r\n\r\n```pytb\r\n\u003e\u003e\u003e from PyQt6.QtCore import Qt\r\n\u003e\u003e\u003e (Qt.KeyboardModifier.ShiftModifier | Qt.KeyboardModifier.ControlModifier) \u0026 ~Qt.KeyboardModifier.ControlModifier\r\nTraceback (most recent call last):\r\n  File \"\u003cstdin\u003e\", line 1, in \u003cmodule\u003e\r\n  File \"/usr/lib/python3.11/enum.py\", line 1542, in __invert__\r\n    self._inverted_ = self.__class__(self._flag_mask_ ^ self._value_)\r\n                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\r\n  File \"/usr/lib/python3.11/enum.py\", line 711, in __call__\r\n    return cls.__new__(cls, value)\r\n           ^^^^^^^^^^^^^^^^^^^^^^^\r\n  File \"/usr/lib/python3.11/enum.py\", line 1136, in __new__\r\n    raise exc\r\n  File \"/usr/lib/python3.11/enum.py\", line 1113, in __new__\r\n    result = cls._missing_(value)\r\n             ^^^^^^^^^^^^^^^^^^^^\r\n  File \"/usr/lib/python3.11/enum.py\", line 1454, in _missing_\r\n    raise ValueError('%r: no members with value %r' % (cls, unknown))\r\nValueError: \u003cflag 'KeyboardModifier'\u003e: no members with value 2147483648\r\n```\r\n\r\nAs a culprit, I suspect:\r\n\r\n- #103365\r\n- #103494\r\n- #103513\r\n\r\ncc @ethanfurman @benburrill\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-105542\n* gh-105571\n* gh-105572\n* gh-106468\n* gh-106620\n* gh-106621\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/The-Compiler","@type":"Person","name":"The-Compiler"},"datePublished":"2023-06-08T12:22:42.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":14},"url":"https://github.com/105497/cpython/issues/105497"}