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GeezerVison is showing github.com — Defer import of json and platform by danielhollas · Pull Request #503 · python/importlib_metadata

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@danielhollas

@danielhollas danielhollas commented Aug 27, 2024

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Staged on top of #502

platform and json modules take together around 1.5ms to import, around 10% of total import time. Since they are both used in a single place it probably makes sense to inline their import.

After this PR, this is an output of python -Ximporttime -c "import importlib_metadata" visualized with tuna using cpython main branch.

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danielhollas added 3 commits August 27, 2024 15:31
@danielhollas
Defer import of zipp
76eebe0
@danielhollas
Defer json import
e0b4f09
@danielhollas
Defer platform import
8436e81
@danielhollas danielhollas mentioned this pull request Aug 27, 2024
Improve import time of various stdlib modules python/cpython#118761
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danielhollas
danielhollas commented Aug 27, 2024
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Comment thread importlib_metadata/_compat.py Resolved

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@jaraco

jaraco commented Sep 11, 2024

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Attempting to disentangle the performance impacts of json and platform:

 importlib_metadata main 🐚 .tox/py/bin/python -Ximporttime -c "import importlib_metadata" 2>1 | grep -E r'platform|\sjson$|importlib_metadata$'
import time:        89 |        800 |   json
import time:       221 |        251 |     platform
import time:       636 |      13692 | importlib_metadata
 importlib_metadata main 🐚 800/13692
0.05842827928717499
 importlib_metadata main 🐚 251/13692
0.018331872626351154

I see json accounts for ~6% of the startup and platform under 2% (on my machine under Python 3.12).
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jaraco
jaraco reviewed Sep 11, 2024
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Comment thread importlib_metadata/_compat.py Resolved

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jaraco added 3 commits September 11, 2024 10:13
@jaraco
Revert "Defer platform import"
18eb2da 
This reverts commit 8436e81.
@jaraco
Add comment to protect the deferred import.
3f78dc1
@jaraco
Add news fragment.
2a3f50d
@jaraco
jaraco merged commit 8b909f9 into python:main Sep 11, 2024
@danielhollas
danielhollas deleted the defer-json branch September 11, 2024 14:27
@danielhollas danielhollas changed the title Defer import of json and zipp Defer import of json and platform Sep 11, 2024
@yashuatla yashuatla mentioned this pull request Jun 22, 2025
Feature implementation from commits 2beb8b0..b34810b yashuatla/importlib_metadata#3
Open
@jaraco jaraco mentioned this pull request Oct 31, 2026
Restore the deferred imports to module scope with PEP 810 lazy imports #554
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@danielhollas @jaraco
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