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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Python 3.12 breaks backwards compatibility for logging configuration","articleBody":"# Bug report\n\n### Bug description:\n\nThis worked fine on previous versions:\n\n```python\nimport logging\nimport logging.config\nimport logging.handlers\nimport multiprocessing as mp\n\n\ndef main():\n    config = {\n        'version': 1,\n        'handlers': {\n            'sink': {\n                'class': 'logging.handlers.QueueHandler',\n                'queue': mp.get_context('spawn').Queue(),\n            },\n        },\n        'root': {\n            'handlers': ['sink'],\n            'level': 'DEBUG',\n        },\n    }\n    logging.config.dictConfig(config)\n\n\nif __name__ == '__main__':\n    main()\n```\n\nWith Python 3.12, it drops an error:\n\n```\nTraceback (most recent call last):\n  File \"/home/egor/.pyenv/versions/3.12-dev/lib/python3.12/logging/config.py\", line 581, in configure\n    handler = self.configure_handler(handlers[name])\n              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/home/egor/.pyenv/versions/3.12-dev/lib/python3.12/logging/config.py\", line 786, in configure_handler\n    raise ValueError('No handlers specified for a QueueHandler')\nValueError: No handlers specified for a QueueHandler\n\nThe above exception was the direct cause of the following exception:\n\nTraceback (most recent call last):\n  File \"/home/egor/workspace/personal/cimple/../test.py\", line 25, in \u003cmodule\u003e\n    main()\n  File \"/home/egor/workspace/personal/cimple/../test.py\", line 21, in main\n    logging.config.dictConfig(config)\n  File \"/home/egor/.pyenv/versions/3.12-dev/lib/python3.12/logging/config.py\", line 912, in dictConfig\n    dictConfigClass(config).configure()\n  File \"/home/egor/.pyenv/versions/3.12-dev/lib/python3.12/logging/config.py\", line 588, in configure\n    raise ValueError('Unable to configure handler '\nValueError: Unable to configure handler 'sink'\n```\n\nMore than that, even the example in the Logging Cookbook is broken now: https://docs.python.org/3/howto/logging-cookbook.html#a-more-elaborate-multiprocessing-example (fails with the same error).\n\nVersion info:\n\n```\n# python -VV\nPython 3.12.0+ (heads/3.12:f108785, Nov  1 2023, 19:47:19) [GCC 13.2.1 20230801]\n```\n\n### CPython versions tested on:\n\n3.12\n\n### Operating systems tested on:\n\nLinux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-111638\n* gh-113507\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/egor-tensin","@type":"Person","name":"egor-tensin"},"datePublished":"2023-11-01T19:34:08.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/111615/cpython/issues/111615"}