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gh-152056: Compile single-category character sets to a bare CATEGORY opcode #152057

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Merged
serhiy-storchaka merged 2 commits into from
Jun 24, 2026
+17 −4
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gh-152056: Compile single-category character sets to a bare CATEGORY opcode #152057

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5c7b797
Compile single-category character sets to a bare CATEGORY opcode
eendebakpt Jun 24, 2026
f95141e
Update What's New and add NEWS.
serhiy-storchaka Jun 24, 2026
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10 changes: 6 additions & 4 deletions Doc/whatsnew/3.16.rst
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Expand Up @@ -288,10 +288,12 @@ re
--

* Character class escapes (``\d``, ``\D``, ``\s``, ``\S``, ``\w`` and ``\W``)
outside a character set are now compiled to a single ``CATEGORY`` opcode
instead of being wrapped in an ``IN`` block. This speeds up matching of
patterns such as ``\d+`` and reduces the size of the compiled byte code.
(Contributed by Serhiy Storchaka in :gh:`152033`.)
outside a character set, and character sets containing a single such escape
(such as ``[\d]`` or ``[^\s]``), are now compiled to a single ``CATEGORY``
opcode instead of being wrapped in an ``IN`` block. This speeds up matching
of patterns such as ``\d+`` and reduces the size of the compiled byte code.
(Contributed by Serhiy Storchaka in :gh:`152033` and Pieter Eendebak in
:gh:`152056`.)

module_name
-----------
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6 changes: 6 additions & 0 deletions Lib/re/_parser.py
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Expand Up @@ -625,6 +625,12 @@ def _parse(source, state, verbose, nested, first=False):
subpatternappend((NOT_LITERAL, set[0][1]))
else:
subpatternappend(set[0])
elif _len(set) == 1 and set[0][0] is CATEGORY:
# optimization: a lone category like [\d] or [^\d]
if negate:
subpatternappend((CATEGORY, CH_NEGATE[set[0][1]]))
else:
subpatternappend(set[0])
else:
if negate:
set.insert(0, (NEGATE, None))
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5 changes: 5 additions & 0 deletions Misc/NEWS.d/next/Library/2026-06-24-10-30-00.gh-issue-152056.Qk7mZ2.rst
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@@ -0,0 +1,5 @@
Optimize matching of a character set that contains a single character
category, such as ``[\d]`` or ``[^\s]``: it is now compiled to a single
``CATEGORY`` opcode, the same as the corresponding ``\d`` or ``\S`` escape,
instead of being wrapped in an ``IN`` block. This speeds up matching and
reduces the size of the compiled byte code. Patch by Pieter Eendebak.
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