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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Defining iterator in a separate class no longer works in 3.13","articleBody":"# Bug report\n\n### Bug description:\n\nDefining an interator for a class in a separate class no longer works properly in 3.13. With the following `test_iter.py`:\n```python\nclass list2(list):\n    def __iter__(self):\n        return list2iterator(self)\n\nclass list2iterator:\n    def __init__(self, X):\n        self._X = X\n        self._pointer = -1\n\n    def __next__(self):\n        self._pointer += 1\n        if self._pointer == len(self._X):\n            self._pointer = -1\n            raise StopIteration\n        return self._X[self._pointer]\n```\nWith Python 3.13.1 one gets:\n```python\n\u003e\u003e\u003e from test_iter import list2\n\u003e\u003e\u003e X=list2([1,2,3])\n\u003e\u003e\u003e [x for x in X]\nTraceback (most recent call last):\n  File \"\u003cpython-input-2\u003e\", line 1, in \u003cmodule\u003e\n    [x for x in X]\n                ^\nTypeError: 'list2iterator' object is not iterable\n```\nWith Python 3.12.7 it works:\n```python\n\u003e\u003e\u003e from test_iter import list2\n\u003e\u003e\u003e X=list2([1,2,3])\n\u003e\u003e\u003e [x for x in X]\n[1, 2, 3]\n```\nBisected to https://github.com/python/cpython/commit/bcc7227e\n\n\n### CPython versions tested on:\n\n3.12, 3.13\n\n### Operating systems tested on:\n\nLinux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-134778\n* gh-134788\n* gh-134799\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/antonio-rojas","@type":"Person","name":"antonio-rojas"},"datePublished":"2024-12-21T19:47:52.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":22},"url":"https://github.com/128161/cpython/issues/128161"}