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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[3.12] Behavior change: __getattr__ gets called after property raises NotImplementedError ","articleBody":"Hi,\r\n\r\n**Version**: `3.12.0a7`\r\n**OS**: Windows\r\n\r\nWhile [testing pytest in 3.12](https://github.com/pytest-dev/pytest/pull/10894#issuecomment-1509303587) on Windows, we noticed an odd behavior that we believe might be a bug/regression.\r\n\r\nConsider this minimal example:\r\n\r\n```python\r\nclass Stat:\r\n    @property\r\n    def owner(self):\r\n        print(\"--\u003e accessing owner\")\r\n        raise NotImplementedError(\"owner not implemented\")\r\n\r\n    def __getattr__(self, item):\r\n        return getattr(1, \"foobar\")\r\n\r\n\r\ns = Stat()\r\ns.owner\r\n``` \r\n\r\n(Using `getattr(1, ...)` there just to have an object in-place; in the real code `1` is actually another object, but the outcome is the same).\r\n\r\nRunning this in Python `3.11.2` (and previous versions), we get this output:\r\n\r\n```\r\nλ py -3.11 --version\r\nPython 3.11.2\r\n\r\nλ py -3.11 .tmp\\reproducer.py\r\n--\u003e accessing owner\r\nTraceback (most recent call last):\r\n  File \"e:\\projects\\pytest\\.tmp\\reproducer.py\", line 12, in \u003cmodule\u003e\r\n    s.owner\r\n  File \"e:\\projects\\pytest\\.tmp\\reproducer.py\", line 5, in owner\r\n    raise NotImplementedError(\"owner not implemented\")\r\nNotImplementedError: owner not implemented\r\n```\r\n\r\n`NotImplementedError` is raised from the property access, and `__getattr__` is never called.\r\n\r\nIn Python `3.12.0a7` however we get:\r\n\r\n```\r\nλ py -3.12 --version\r\nPython 3.12.0a7\r\n\r\nλ py -3.12 .tmp\\reproducer.py\r\n--\u003e accessing owner\r\nTraceback (most recent call last):\r\n  File \"e:\\projects\\pytest\\.tmp\\reproducer.py\", line 12, in \u003cmodule\u003e\r\n    s.owner\r\n  File \"e:\\projects\\pytest\\.tmp\\reproducer.py\", line 8, in __getattr__\r\n    return getattr(1, \"foobar\")\r\n           ^^^^^^^^^^^^^^^^^^^^\r\nAttributeError: 'int' object has no attribute 'foobar'\r\n```\r\n\r\nThe property is still being accessed (as shown by the `print` call), but `NotImplementedError` is being swallowed/ignored, and `__getattr__` seems to be getting called as a fallback.\r\n\r\n---\r\n\r\nChanging the example slightly:\r\n\r\n```python\r\nclass Stat:\r\n    @property\r\n    def owner(self):\r\n        print(\"--\u003e accessing owner\")\r\n        raise NotImplementedError(\"owner not implemented\")\r\n\r\n    def __getattr__(self, item):\r\n        raise AttributeError(\"foobar\")\r\n\r\n\r\ns = Stat()\r\ns.owner\r\n```\r\n\r\nIn Python `3.11` the behavior stays the same as before, however in Python `3.12` we now get:\r\n\r\n```\r\nλ py -3.12 .tmp\\reproducer.py\r\n--\u003e accessing owner\r\nTraceback (most recent call last):\r\n  File \"e:\\projects\\pytest\\.tmp\\reproducer.py\", line 5, in owner\r\n    raise NotImplementedError(\"owner not implemented\")\r\nNotImplementedError: owner not implemented\r\n\r\nThe above exception was the direct cause of the following exception:\r\n\r\nTraceback (most recent call last):\r\n  File \"e:\\projects\\pytest\\.tmp\\reproducer.py\", line 12, in \u003cmodule\u003e\r\n    s.owner\r\n  File \"e:\\projects\\pytest\\.tmp\\reproducer.py\", line 8, in __getattr__\r\n    raise AttributeError(\"foobar\")\r\n          ^^^^^^^^^^^^^^^^^^^^^^^^\r\nSystemError: \u003cclass 'AttributeError'\u003e returned a result with an exception set\r\n```\r\n\r\nPlease let us know if you need more information.","author":{"url":"https://github.com/nicoddemus","@type":"Person","name":"nicoddemus"},"datePublished":"2023-04-14T23:37:23.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/103551/cpython/issues/103551"}