René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"`_pickle.PicklingError` on 3.14.0a1+ where it didn't before due to the start method change from fork to forkserver","articleBody":"# Bug report\n\n### Bug description:\n\nCode dating back to Python 2 had to do `super(OwnClassName, self)` instead of `super()`. Modules designed to be reloadable could not use the `super(OwnClassName, self)` syntax in their non-constructor method, as `OwnClassName` was re-binded to the class of the new module, rather than the class that had the name when the object was constructed (which differs when the object was constructed before a reload). Therefore, such modules defined classes like this:\n\n```python\nclass Subclass(Superclass):\n    def __init__(self):\n        self.__parent = super(Subclass, self)\n\n    def method1(self, arg):\n        self.__parent.method1(arg + 2)\n```\n\nPython 3.14.0a1+ breaks existing code using this trick on subclasses of `multiprocessing.Process`.\n\nFor example:\n\n```python\nimport multiprocessing\n\nclass MyProcess(multiprocessing.Process):\n    def __init__(self, target=None, args=(), kwargs={}):\n        self.__parent = super(MyProcess, self)\n        self.__parent.__init__(target=target, args=args, kwargs=kwargs)\n\n    def run(self):\n        self.__parent.run()\n    \nif __name__ == \"__main__\":\n    p = MyProcess()\n    p.start()\n```\n\nworked fine on previous versions, but now errors with:\n\n```\nTraceback (most recent call last):\n  File \"/home/dev-irc/Limnoria/repro.py\", line 12, in \u003cmodule\u003e\n    p.start()\n    ~~~~~~~^^\n  File \"/home/dev-irc/.local-py-git/lib/python3.14/multiprocessing/process.py\", line 121, in start\n    self._popen = self._Popen(self)\n                  ~~~~~~~~~~~^^^^^^\n  File \"/home/dev-irc/.local-py-git/lib/python3.14/multiprocessing/context.py\", line 224, in _Popen\n    return _default_context.get_context().Process._Popen(process_obj)\n           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^\n  File \"/home/dev-irc/.local-py-git/lib/python3.14/multiprocessing/context.py\", line 300, in _Popen\n    return Popen(process_obj)\n  File \"/home/dev-irc/.local-py-git/lib/python3.14/multiprocessing/popen_forkserver.py\", line 35, in __init__\n    super().__init__(process_obj)\n    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^\n  File \"/home/dev-irc/.local-py-git/lib/python3.14/multiprocessing/popen_fork.py\", line 20, in __init__\n    self._launch(process_obj)\n    ~~~~~~~~~~~~^^^^^^^^^^^^^\n  File \"/home/dev-irc/.local-py-git/lib/python3.14/multiprocessing/popen_forkserver.py\", line 47, in _launch\n    reduction.dump(process_obj, buf)\n    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^\n  File \"/home/dev-irc/.local-py-git/lib/python3.14/multiprocessing/reduction.py\", line 60, in dump\n    ForkingPickler(file, protocol).dump(obj)\n    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^\n_pickle.PicklingError: first argument to __newobj__() must be \u003cclass 'super'\u003e, not \u003cclass '__main__.MyProcess'\u003e\nwhen serializing super object\nwhen serializing dict item '_MyProcess__parent'\nwhen serializing MyProcess state\nwhen serializing MyProcess object\n```\n\nFull version string: `Python 3.14.0a1+ (heads/main:c8fd4b12e3d, Oct 18 2024, 22:51:39) [GCC 12.2.0] on linux`\n\n### CPython versions tested on:\n\n3.14, CPython main branch\n\n### Operating systems tested on:\n\nLinux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-125750\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/progval","@type":"Person","name":"progval"},"datePublished":"2024-10-18T21:20:28.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":11},"url":"https://github.com/125714/cpython/issues/125714"}