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gh-117865: Speedup import of inspect module#144756

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hugovk merged 8 commits into
python:mainfrom
danielhollas:speedup-inspect-import-lazy
Mar 2, 2026
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gh-117865: Speedup import of inspect module#144756
hugovk merged 8 commits into
python:mainfrom
danielhollas:speedup-inspect-import-lazy

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@danielhollas

@danielhollas danielhollas commented Feb 12, 2026 •
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This is a revived version of #119526 (with Alex's blessing), using the new fancy lazy import machinery to defer imports of re and tokenize modules, for a ~20% speedup.

Before

image 
❯ hyperfine -w 5 "./python -c 'import inspect'"
Benchmark 1: ./python -c 'import inspect'
  Time (mean ± σ):      19.2 ms ±   1.9 ms    [User: 14.4 ms, System: 4.5 ms]
  Range (min … max):    16.3 ms …  23.4 ms    152 runs

After

image 
❯ hyperfine -w 5 "./python -c 'import inspect'"
Benchmark 1: ./python -c 'import inspect'
  Time (mean ± σ):      16.4 ms ±   2.0 ms    [User: 12.3 ms, System: 3.9 ms]
  Range (min … max):    13.8 ms …  22.2 ms    191 runs

Part of #137855

AlexWaygood and others added 3 commits February 12, 2026 17:01
@AlexWaygood @danielhollas
Speedup import inspect
9006af2
@danielhollas
Don't defer ast import …
408e1ad 
While we can easily make ast import lazy in inspect module,
it is anyway imported in annotationlib, which cannot be made lazy.
@danielhollas
Use PEP810!
fdacefb
@bedevere-app bedevere-app Bot mentioned this pull request Feb 12, 2026
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JelleZijlstra
JelleZijlstra approved these changes Feb 13, 2026
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@JelleZijlstra JelleZijlstra left a comment

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Makes sense. re is used only in one place in formatannotation, so many users won't need it. tokenize is used a bit more heavily but most of the API in the module still won't need it.

@bedevere-app bedevere-app Bot added awaiting merge and removed labels Feb 13, 2026
@danielhollas

danielhollas commented Mar 1, 2026

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Hi all,

just a kind ping to see if this PR could be merged. 😊

Hide details View details @hugovk hugovk merged commit ea90b03 into python:main Mar 2, 2026
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@danielhollas danielhollas deleted the speedup-inspect-import-lazy branch March 2, 2026 22:31
ljfp pushed a commit to ljfp/cpython that referenced this pull request Apr 25, 2026
@danielhollas @AlexWaygood @ljfp
pythongh-117865: Speedup import of inspect module (python#144756) …
9d828a0 
Co-authored-by: Alex Waygood <alex.waygood@gmail.com>
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@JelleZijlstra JelleZijlstra JelleZijlstra approved these changes

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@danielhollas @JelleZijlstra @hugovk @AlexWaygood