Description

maxday

opened on Aug 25, 2026

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rlcompleter imports inspect and re at module scope, but neither is needed to import the module or to construct a Completer. Each is used in exactly one completion method:

• inspect: only in Completer._callable_postfix
• re: only in Completer.attr_matches

inspect in particular is a heavy import: it transitively pulls in dis, tokenize, and more. Because rlcompleter is imported during interactive startup (to set up tab completion via readline), this import cost is paid on every interactive session and every import rlcompleter, even though the completion methods may never run.

Linked PRs

• gh-156363: Speed up import of rlcompleter by deferring inspect and re #156364

Activity

1. maxday commented on Aug 25, 2026

   

   maxday

   on Aug 25, 2026

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   I'm working on this :)
2. maxday

   added 2 commits that reference this issue on Aug 25, 2026

   pythongh-156363: Speed up import of rlcompleter by deferring inspect …

   aa2ebff

   pythongh-156363: Speed up import of rlcompleter by deferring inspect …

   fadfaf9
3. aisk

   added

   performancePerformance or resource usagePerformance or resource usage

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   on Aug 25, 2026
4. hugovk

   added a parent issue on Aug 25, 2026

   • Improve import time of various stdlib modules #154675
5. maxday

   added 2 commits that reference this issue on Aug 25, 2026

   pythongh-156363: Use PEP 810 lazy imports for inspect and re in rlcom…

   0ba9e10

   pythongh-156363: Use PEP 810 lazy imports for inspect and re in rlcom…

   a79e157
6. StanFromIreland

   added

   type-featureA feature request or enhancementA feature request or enhancement

   on Aug 26, 2026
7. aisk commented on Aug 26, 2026

   

   aisk

   on Aug 26, 2026

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   One thing to notice, on the interactive startup path these two modules get imported a moment later anyway, since _pyrepl.readline is imported right after rlcompleter and pulls them both in:

   $ ./python -c "import sys, _pyrepl.readline; print('re' in sys.modules, 'inspect' in sys.modules)"
   True True

   So the gain doesn't really materialize for the interactive interpreter. It may still help people who use this module on its own, though.
8. maxday commented on Aug 28, 2026

   

   maxday

   on Aug 28, 2026

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   You're right @aisk, on the default PyREPL path _pyrepl.readline pulls in both re (directly) and inspect (via dataclasses(slots=True) in _pyrepl/utils.py), so the deferral is neutral there.

   It does still help in two cases: PYTHON_BASIC_REPL=1, where site.py skips the _pyrepl.readline import entirely, and standalone use of rlcompleter (e.g. readline.set_completer(rlcompleter.Completer(ns).complete)), where importing the module drops from ~15 ms to ~1.6 ms and avoids ~35 transitive modules.

   It also helps people who use this module on its own indeed.

   Since it's neutral on the common path and a win on the others and in line with the ongoing startup-time / PEP 810 work, I think it's still worth doing, let me know!
9. seth-957

   added a commit that references this issue on Sep 6, 2026

   pythongh-156363, pythongh-156491: Speed up rlcompleter import and opt…

   c8cf419
10. StanFromIreland

    closed this as not plannedon Oct 22, 2026

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