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GeezerVison is showing github.com — gh-150942: Improve performance of csv reader by using _PyList_AppendT… by imabd645 · Pull Request #155957 · python/cpython

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@imabd645

@imabd645 imabd645 commented Aug 17, 2026 •
edited by bedevere-app Bot
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Description

This PR improves the performance of the csv module's reader by replacing standard PyList_Append calls with the internal _PyList_AppendTakeRef stealing method.

When parsing CSV fields, the C extension previously appended the parsed field to a list and subsequently decremented the reference count of the field. By using the new stealing methods, we avoid the overhead of an unnecessary incref/decref pair and slightly simplify the C implementation.

Changes:

  • Included "pycore_list.h" in Modules/_csv.c.
  • Replaced PyList_Append followed by Py_DECREF with _PyList_AppendTakeRef in the parse_save_field function.
  • Added the corresponding NEWS blurb.
  • Issue: Improve performance by using reference stealing methods #150942

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@imabd645
pythongh-150942: Improve performance of csv reader by using _PyList_A…
a2bfdd6 
…ppendTakeRef
@bedevere-app bedevere-app Bot mentioned this pull request Aug 17, 2026
Improve performance by using reference stealing methods #150942
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@bedevere-app bedevere-app Bot added the awaiting review label Aug 17, 2026
@eendebakpt

eendebakpt commented Aug 17, 2026

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Duplicate of #150995?
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@StanFromIreland

StanFromIreland commented Aug 17, 2026

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Closing in favour of the older PR.
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@StanFromIreland StanFromIreland closed this Aug 17, 2026
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3 participants

@imabd645 @eendebakpt @StanFromIreland
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