Bug report

Bug description:

datetime.replace() is very slow when called with keyword arguments. For example, with python 3.13 from main on my laptop

$python -m timeit -s"from datetime import datetime; dt = datetime.now()""dt.replace(microsecond=0)"500000 loops, best of 5: 501 nsec per loop

For comparison,

$python -m timeit -s"from datetime import datetime""datetime.now()"2000000 loops, best of 5: 150 nsec per loop$python -m timeit -s"from datetime import datetime""datetime(2020, 1, 1, 12, 34, 56, 123456)"2000000 loops, best of 5: 119 nsec per loop

So calling replace() is over 4x slower than constructing a new datetime from components and over 3x slower than now(), which makes a system call.

CPython versions tested on:

3.9, 3.10, 3.13

Operating systems tested on:

Linux

Linked PRs

• gh-112919: Speed-up datetime, date and time.replace() #112921
• [3.12] gh-112919: Speed-up datetime, date and time.replace() (GH-112921) #115344