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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Inconsistent error messages when returning the wrong type for the type-conversion magic methods","articleBody":"# Bug report\n\n### Bug description:\n\nI noticed the error messages between magic methods like `__int__` and `__float__` were inconsistent. This seems like slightly undesirable behavior to me. I used the following code to generate many of them.\n\n```python\nclass Foo:\n    def __int__(self):\n        return None\n    \n    def __float__(self):\n        return None\n    \n    def __bytes__(self):\n        return None\n    \n    def __complex__(self):\n        return None\n    \n    def __bool__(self):\n        return None\n    \n    def __str__(self):\n        return None\n\ntry:\n    int(Foo())\nexcept Exception as e:\n    print(e)\n\ntry:\n    float(Foo())\nexcept Exception as e:\n    print(e)\n\ntry:\n    bytes(Foo())\nexcept Exception as e:\n    print(e)\n\ntry:\n    complex(Foo())\nexcept Exception as e:\n    print(e)\n\ntry:\n    bool(Foo())\nexcept Exception as e:\n    print(e)\n\ntry:\n    str(Foo())\nexcept Exception as e:\n    print(e)\n```\n\nAnd the output is as follows:\n\n```python\n__int__ returned non-int (type NoneType)\nFoo.__float__ returned non-float (type NoneType)\n__bytes__ returned non-bytes (type NoneType)\n__complex__ returned non-complex (type NoneType)\n__bool__ should return bool, returned NoneType\n__str__ returned non-string (type NoneType)\n```\nThe first issue I've made, but seems like a reasonable bug. I'm not sure if there are other \"type-conversion\" magic methods out there that aren't consistent.\n\n### CPython versions tested on:\n\n3.13, 3.12\n\n### Operating systems tested on:\n\nWindows\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-130835\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/mxgordon","@type":"Person","name":"mxgordon"},"datePublished":"2025-03-04T07:28:08.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":14},"url":"https://github.com/130821/cpython/issues/130821"}