René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"co_instrumentation and co_monitoring Unexpectedly Set","articleBody":"# Bug report\n\n### Bug description:\n\nI ran into the following problematic case with gh-133221 (which had to be reverted):\n\n```python\nimport sys\nimport _testinternalcapi\n\ndef foo():\n    pass\n\ndef trace_temporarily():\n    sys._getframe().f_trace_opcodes = True\n    sys.settrace(print)\n    sys.settrace(None)\n    sys._getframe().f_trace_opcodes = False\ntrace_temporarily()\n\n_testinternalcapi.verify_stateless_code(foo.__code__)\nfoo()\n_testinternalcapi.verify_stateless_code(foo.__code__)  # fails\n```\n\n(See https://github.com/python/cpython/pull/133221#issuecomment-2853467104.)\n\nI would expect `co_instrumentation` and `co_monitoring` to have remained NULL.\n\nCC @markshannon \n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\n_No response_","author":{"url":"https://github.com/ericsnowcurrently","@type":"Person","name":"ericsnowcurrently"},"datePublished":"2025-05-06T15:26:30.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/133524/cpython/issues/133524"}