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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"3.12.0b4 Backwards incompatible change with reassignment of `cls.__new__` and `super()`","articleBody":"\u003c!--\r\n  If you're new to Python and you're not sure whether what you're experiencing is a bug, the CPython issue tracker is not\r\n  the right place to seek help. Consider the following options instead:\r\n\r\n  - reading the Python tutorial: https://docs.python.org/3/tutorial/\r\n  - posting in the \"Users\" category on discuss.python.org: https://discuss.python.org/c/users/7\r\n  - emailing the Python-list mailing list: https://mail.python.org/mailman/listinfo/python-list\r\n  - searching our issue tracker (https://github.com/python/cpython/issues) to see if\r\n    your problem has already been reported\r\n--\u003e\r\n\r\n# Bug report\r\n\r\nNoticed this while testing `3.12.0b4`. While in my particular case I can work around it, it never the less is a change in behavior to `3.11`.\r\n\r\n```py\r\nclass FixedIntType(int):\r\n    _signed: bool\r\n\r\n    def __new__(cls, *args, **kwargs):\r\n        print(f\"{cls}, {args=}\")\r\n        return super().__new__(cls, *args, **kwargs)\r\n\r\n    def __init_subclass__(cls, signed: int | None = None) -\u003e None:\r\n        super().__init_subclass__()\r\n        if signed is not None:\r\n            cls._signed = signed\r\n\r\n        if \"__new__\" not in cls.__dict__:\r\n            cls.__new__ = cls.__new__  # \u003c-- This line triggers the error\r\n\r\nclass uint_t(FixedIntType, signed=False):\r\n    pass\r\n\r\nclass CustomInt(uint_t):\r\n    def __new__(cls, value: int = 0):\r\n        return super().__new__(cls, value)\r\n\r\n    def with_id(self, value: int):\r\n        return type(self)(value)\r\n\r\nCustomInt().with_id(1024)\r\n```\r\n\r\n```\r\n\u003cclass '__main__.CustomInt'\u003e, args=(0,)\r\n\u003cclass '__main__.CustomInt'\u003e, args=(\u003cclass '__main__.CustomInt'\u003e, 1024)\r\nTraceback (most recent call last):\r\n  File \"/.../cpython/test.py\", line 26, in \u003cmodule\u003e\r\n    CustomInt().with_id(1024)\r\n  File \"/.../cpython/test.py\", line 24, in with_id\r\n    return type(self)(value)\r\n           ^^^^^^^^^^^^^^^^^\r\n  File \"/.../cpython/test.py\", line 21, in __new__\r\n    return super().__new__(cls, value)\r\n           ^^^^^^^^^^^^^^^^^^^^^^^^^^^\r\n  File \"/.../cpython/test.py\", line 6, in __new__\r\n    return super().__new__(cls, *args, **kwargs)\r\n           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\r\nValueError: int() base must be \u003e= 2 and \u003c= 36, or 0\r\n```\r\n\r\nWithout `cls.__new__ = cls.__new__`\r\n```\r\n\u003cclass '__main__.CustomInt'\u003e, args=(0,)\r\n\u003cclass '__main__.CustomInt'\u003e, args=(1024,)\r\n```\r\n\r\nI bisected the issue to #103497.\r\n/CC: @carljm\r\n\r\n# Your environment\r\n\r\n- CPython versions tested on: `3.120b4`\r\n- Operating system and architecture: macOS ARM64\r\n\r\n\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-106977\n* gh-107204\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/cdce8p","@type":"Person","name":"cdce8p"},"datePublished":"2023-07-20T16:16:55.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/106917/cpython/issues/106917"}