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GeezerVison is showing github.com — gh-156185: Ignore all ASCII whitespace in re \p{} property names by Georgefifth · Pull Request #156304 · python/cpython

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@Georgefifth

@Georgefifth Georgefifth commented Aug 24, 2026 •
edited by bedevere-app Bot
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Problem
The docs (and the _normalize comment) promise that \p{...} property and value names are matched loosely — case, whitespace, hyphens and underscores are not significant (UAX #44, LM3). In practice only spaces were removed, so \p{L\tu} or \p{G\nC=Lu} raised re.error: unknown property "L\ntu" while the space form worked. (3.16-only feature, so no compatibility concern.)

Solution
_normalize() in Lib/re/_properties.py now drops all ASCII whitespace ( \t\n\r\f\v), not just space; comment updated to match.

Result
Added a regression loop over all six whitespace characters in test_re.py::test_property_escapes; full test_re passes (169 tests) on a debug build, and the new assertions fail on the unpatched code. NEWS entry added.

  • Issue: \p{...} names ignore only spaces, though the docs promise whitespace #156185

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@python-cla-bot

python-cla-bot Bot commented Aug 24, 2026 •
edited
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All commit authors signed the Contributor License Agreement.

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@bedevere-app bedevere-app Bot added the awaiting review label Aug 24, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Aug 24, 2026
\p{...} names ignore only spaces, though the docs promise whitespace #156185
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serhiy-storchaka
serhiy-storchaka reviewed Aug 27, 2026
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Comment thread Lib/re/_properties.py Outdated
# hyphens and underscores are not significant, and an initial "is" prefix
# is ignored (UAX #44 5.9, "Matching Rules", UAX44-LM3;
# Unicode property and value names are matched loosely: case, whitespace
# and hyphens and underscores are not significant, and an initial "is"

@serhiy-storchaka serhiy-storchaka Aug 27, 2026

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Double "and".

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Comment thread Lib/re/_properties.py Outdated
# prefix is ignored (UAX #44 5.9, "Matching Rules", UAX44-LM3;
# https://www.unicode.org/reports/tr44/).
name = name.lower().replace("_", "").replace("-", "").replace(" ", "")
name = "".join(ch for ch in name.lower() if ch not in " \t\n\r\f\v_-")

@serhiy-storchaka serhiy-storchaka Aug 27, 2026

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This code is significantly slower than a sequence of replaces. The fastest method is to use translate() with predefined table created by str.maketrans().

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serhiy-storchaka
serhiy-storchaka reviewed Aug 27, 2026
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Also, no NEWS entry is needed. This is a fix of an unreleased feature.

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@bedevere-app

bedevere-app Bot commented Aug 28, 2026

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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.
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@Georgefifth
pythongh-156185: Ignore all ASCII whitespace in re \p{} property names
0bfce66
@Georgefifth
Georgefifth force-pushed the fix/re-property-whitespace branch from 8b94a7c to 0bfce66 Compare August 28, 2026 23:21
@bedevere-app

bedevere-app Bot commented Aug 28, 2026

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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.
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Georgefifth
Georgefifth commented Aug 28, 2026
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All three addressed in 0bfce66:

  • Double "and" — fixed, the comment now reads "case, whitespace, hyphens and underscores".
  • translate() — the strip is now name.lower().translate(_NON_SIGNIFICANT) with the table built once via str.maketrans("", "", " \t\n\r\f\v_-") at module level. Measured on a 33-char name: ~1.4x faster than the generator expression.
  • NEWS — removed; it is a fix to an unreleased feature, as you said.

test_re passes on a locally built interpreter (169 tests, 3 skipped, all pre-existing skips).

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@Georgefifth @serhiy-storchaka
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