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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Generator expression behavior changed in 3.13.4 - it does not throw exception anymore","articleBody":"# Bug report\n\n### Bug description:\n\nIn 3.13.3 and before \n```pycon\n\u003e\u003e\u003e bool(_ for item in False)\nTraceback (most recent call last):\n  File \"\u003cpython-input-14\u003e\", line 1, in \u003cmodule\u003e\n    bool(_ for item in False)\n                       ^^^^^\nTypeError: 'bool' object is not iterable\n\u003e\u003e\u003e (_ for item in False)\nTraceback (most recent call last):\n  File \"\u003cpython-input-15\u003e\", line 1, in \u003cmodule\u003e\n    (_ for item in False)\n                   ^^^^^\nTypeError: 'bool' object is not iterable\n```\n\nNow in 3.13.4\n```pycon\n\u003e\u003e\u003e bool(_ for item in False)\nTrue\n\u003e\u003e\u003e (_ for item in False)\n\u003cgenerator object \u003cgenexpr\u003e at 0xffffa9c02200\u003e\n```\nThis is very fundamental change. Is it expected?\n\n### CPython versions tested on:\n\n3.13\n\n### Operating systems tested on:\n\nLinux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-135225\n* gh-135293\n* gh-135351\n* gh-135352\n* gh-135390\n* gh-135403\n* gh-135524\n* gh-135525\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/Roman513","@type":"Person","name":"Roman513"},"datePublished":"2025-06-05T10:12:42.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":34},"url":"https://github.com/135171/cpython/issues/135171"}