[3.12] gh-98820: Fix quadratic time in csv.Sniffer for quoted fields (GH-154867) - #155166
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Yhg1s merged 1 commit intoAug 4, 2026
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…ields (pythonGH-154867) (cherry picked from commit b30c7fa)
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Thanks @serhiy-storchaka for the PR, and @Yhg1s for merging it 🌮🎉.. I'm working now to backport this PR to: 3.10, 3.11. |
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Sorry, @serhiy-storchaka and @Yhg1s, I could not cleanly backport this to 3.11 due to a conflict. cherry_picker 063d4555c94ef412c731527dbf30193327f2ee82 3.11 |
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Sorry, @serhiy-storchaka and @Yhg1s, I could not cleanly backport this to 3.10 due to a conflict. cherry_picker 063d4555c94ef412c731527dbf30193327f2ee82 3.10 |
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This was referenced Aug 11, 2026
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Manual backport of #154867 to the security branch, cherry-picked from the 3.13 backport (commit b30c7fa).
The only conflict was in Lib/csv.py: 3.12 does not have gh-103925, so its patterns end with (?:$|\n) where the 3.13 pre-image had (?:$|\r|\n). After the resolution _guess_quote_and_delimiter() is identical to the 3.13 one.
Sniffing '"abcdefghijklmnopqrstuvwxyz"\n' * n with delimiters=',:|\t' takes 0.248, 0.977, 3.891 and 15.316 s for n = 1250, 2500, 5000 and 10000 before the change, and 0.026, 0.055, 0.109 and 0.216 s after it.