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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Inaccurate emulation of _PyType_Lookup() in the Descriptor HOWTO","articleBody":"# Documentation\r\n\r\nDoc link: https://docs.python.org/3.10/howto/descriptor.html#invocation-from-an-instance\r\n\r\nSource: https://github.com/python/cpython/blame/eb81c1aea16914347919745e843c982ed831a9fb/Doc/howto/descriptor.rst#L585-L601\r\n\r\nThe code example is bad at https://github.com/python/cpython/blame/eb81c1aea16914347919745e843c982ed831a9fb/Doc/howto/descriptor.rst#L589\r\n\r\n`getattr(objtype, name)` will go through `descriptor.__get__`.\r\n\r\nCode Snippet:\r\n\r\n```python\r\nclass A:\r\n    def __get__(self, obj, objtype):\r\n        return obj, objtype\r\n\r\nclass B:\r\n    a = A()\r\n\r\nprint(B().a)\r\n# (\u003c__main__.B object at 0x7ff56d0915e0\u003e, \u003cclass '__main__.B'\u003e)\r\nprint(B.a)  # same as getattr\r\n# (None, \u003cclass '__main__.B'\u003e)\r\n```\r\n\r\n## Solution\r\n\r\nUsing `__dict__` (or vars) instead of `getattr`:\r\n\r\n```python\r\nprint(vars(B)['a'])\r\n# \u003c__main__.A object at 0x7ff56cfef2b0\u003e\r\n```\r\n","author":{"url":"https://github.com/iyume","@type":"Person","name":"iyume"},"datePublished":"2022-08-09T13:42:25.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/95822/cpython/issues/95822"}