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GeezerVison is showing github.com — Lazy load urllib modules in saxutils · Issue #159675 · python/cpython

Lazy load urllib modules in saxutils #159675

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Lazy load urllib modules in saxutils#159675
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stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directorytopic-lazy-importstype-featureA feature request or enhancementA feature request or enhancement

Description

@jelly
jelly
opened on Oct 18, 2026
Issue body actions

Feature or enhancement

import xml.sax.saxutils

Firewalld, a popular Linux firewall daemon uses xml.sax to read/write XML files, like most other consumers it does not call prepare_input_source() which is the only function which relies on the urllib imports.

Lazily loading the modules shaves off 3M memory usage (48M before -> 45M after), additionally it makes importing saxutils 3x faster but that is not super important.

Before:

[jelle@natrium][~/projects/cpython]%hyperfine -w 5 "./python -c 'import xml.sax.saxutils'"
Benchmark 1: ./python -c 'import xml.sax.saxutils' (85 runs)
                mean     ±       σ          min     …     max
  Wall Time     34.3 ms  ±     1.4 ms      32.6 ms  …    42.0 ms
  Memory        20.3 MiB ±     0.2 MiB     19.7 MiB …    20.6 MiB

After

[jelle@natrium][~/projects/cpython]%hyperfine -w 5 "./python -c 'import xml.sax.saxutils'"
Benchmark 1: ./python -c 'import xml.sax.saxutils' (271 runs)
                mean     ±       σ          min     …     max
  Wall Time     10.6 ms  ±     0.5 ms       9.1 ms  …    11.6 ms
  Memory        10.2 MiB ±     0.1 MiB      9.8 MiB …    10.4 MiB

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

  • gh-159675: Use lazy urllib imports in saxutils #159676

Activity

  1. jelly
    added
    type-featureA feature request or enhancementA feature request or enhancement
    on Oct 18, 2026
  2. hugovk
    added a parent issue on Oct 18, 2026
    • Improve import time of various stdlib modules #154675
  3. aisk
    added
    topic-lazy-imports
    on Oct 18, 2026
  4. picnixz
    added
    stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory
    on Oct 18, 2026
  5. kevinprimeraquecreo-stack
    added this to Project_VKand Project_VKon Oct 18, 2026
  6. github-project-automation
    moved this to Todo in Project_VKon Oct 18, 2026
  7. StanFromIreland
    added a commit that references this issue on Oct 19, 2026

    gh-159675: Tidy and lazify imports in `xml.sax.saxutils` (#159676)

    2dd5315
  8. StanFromIreland
    closed this as completedon Oct 19, 2026
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