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GeezerVison is showing github.com — gh-137855: Improve import time of dataclasses by lazy importing `re` and `copy` modules by danielhollas · Pull Request #148379 · python/cpython

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danielhollas commented Apr 11, 2026 •

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Split from #144387 as requested by @hugovk (tagging for review :-) This is a relatively minor win, the bigger win will come from lazy importing inspect in #144387

See below for tuna-visualized outputs from ./python -X importtime -c "import dataclasses"
(the absolute import numbers are not representative as I was running a debug python build)

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Issue: Improve import time of various stdlib modules #137855

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danielhollas added 3 commits

April 11, 2026 12:30


          Lazy import copy module

5206a52


          Lazy import re module

dca8fc3


          Add blurb

91473a5

danielhollas requested a review from ericvsmith as a code owner

April 11, 2026 12:23

bedevere-app Bot added the awaiting review label

Apr 11, 2026

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Apr 11, 2026

Improve import time of various stdlib modules #137855

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danielhollas mentioned this pull request

Apr 11, 2026

gh-137855: Lazy import inspect module in dataclasses #144387

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Apr 11, 2026

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Lib/dataclasses.py Resolved

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Lib/dataclasses.py Resolved

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Lib/dataclasses.py Resolved

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danielhollas and others added 4 commits

April 11, 2026 17:19


          Update Lib/dataclasses.py

Co-authored-by: Hugo van Kemenade <[email protected]>


          Reorder lazy imports

ab4bc95


          Hugo's regex-fu

933a9c5


          One more match

51fecc5

danielhollas commented Apr 11, 2026

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The failing Ubuntu build is a transient issue during dependency installation that will hopefully go away when the job is restarted.

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hugovk approved these changes

Apr 11, 2026

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bedevere-app Bot added awaiting merge and removed awaiting review labels

Apr 11, 2026

hugovk enabled auto-merge (squash)

April 11, 2026 20:47

hugovk merged commit dd2735d into python:main

Apr 11, 2026

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bedevere-app Bot removed the awaiting merge label

Apr 11, 2026

danielhollas deleted the dataclass-lazy-re branch

April 11, 2026 21:12

danielhollas mentioned this pull request

Apr 11, 2026

gh-148406: Fix annotations of _colorize.FancyCompleter #148408

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ljfp pushed a commit to ljfp/cpython that referenced this pull request

Apr 25, 2026


          pythongh-137855: Improve import time of dataclasses by lazy importing…

db4cffa

… `re` and `copy` modules (python#148379)

Co-authored-by: Hugo van Kemenade <[email protected]>

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danielhollas commented Apr 11, 2026 • edited by bedevere-app Bot Loading Uh oh! There was an error while loading. Please reload this page.

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danielhollas commented Apr 11, 2026 •

edited by bedevere-app Bot

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