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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"datetime.replace() is very slow","articleBody":"# Bug report\r\n\r\n### Bug description:\r\n\r\ndatetime.replace() is very slow when called with keyword arguments. For example, with python 3.13 from main on my laptop\r\n```console\r\n$ python -m timeit -s \"from datetime import datetime; dt = datetime.now()\" \"dt.replace(microsecond=0)\"\r\n500000 loops, best of 5: 501 nsec per loop\r\n```\r\nFor comparison,\r\n```console\r\n$ python -m timeit -s \"from datetime import datetime\" \"datetime.now()\"\r\n2000000 loops, best of 5: 150 nsec per loop\r\n$ python -m timeit -s \"from datetime import datetime\" \"datetime(2020, 1, 1, 12, 34, 56, 123456)\"\r\n2000000 loops, best of 5: 119 nsec per loop\r\n```\r\nSo calling replace() is over 4x slower than constructing a new datetime from components and over 3x slower than now(), which makes a system call.\r\n\r\n### CPython versions tested on:\r\n\r\n3.9, 3.10, 3.13\r\n\r\n### Operating systems tested on:\r\n\r\nLinux\r\n\r\n\u003c!-- gh-linked-prs --\u003e\r\n### Linked PRs\r\n* gh-112921\r\n* gh-115344\n\u003c!-- /gh-linked-prs --\u003e\r\n","author":{"url":"https://github.com/eltoder","@type":"Person","name":"eltoder"},"datePublished":"2023-12-10T05:06:38.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/112919/cpython/issues/112919"}