https://github.com/python/cpython/commit/44b73d3cd4466e148460883acf4494124eae8c91
commit: 44b73d3cd4466e148460883acf4494124eae8c91
branch: main
author: Serhiy Storchaka <storch...@gmail.com>
committer: encukou <encu...@gmail.com>
date: 2025-05-19T15:27:50+02:00
summary:
gh-122055: Clarify documentation for empty matches in RE (GH-133169)
files:
M Doc/library/re.rst
diff --git a/Doc/library/re.rst b/Doc/library/re.rst
index eb3b1e5549cc98..75ebbf11c8e47c 100644
--- a/Doc/library/re.rst
+++ b/Doc/library/re.rst
@@ -991,8 +991,8 @@ Functions
That way, separator components are always found at the same relative
indices within the result list.
- Empty matches for the pattern split the string only when not adjacent
- to a previous empty match.
+ Adjacent empty matches are not possible, but an empty match can occur
+ immediately after a non-empty match.
.. code:: pycon
@@ -1095,9 +1095,12 @@ Functions
The optional argument *count* is the maximum number of pattern occurrences
to be
replaced; *count* must be a non-negative integer. If omitted or zero, all
- occurrences will be replaced. Empty matches for the pattern are replaced
only
- when not adjacent to a previous empty match, so ``sub('x*', '-', 'abxd')``
returns
- ``'-a-b--d-'``.
+ occurrences will be replaced.
+
+ Adjacent empty matches are not possible, but an empty match can occur
+ immediately after a non-empty match.
+ As a result, ``sub('x*', '-', 'abxd')`` returns ``'-a-b--d-'``
+ instead of ``'-a-b-d-'``.
.. index:: single: \g; in regular expressions
@@ -1128,8 +1131,7 @@ Functions
.. versionchanged:: 3.7
Unknown escapes in *repl* consisting of ``'\'`` and an ASCII letter
now are errors.
- Empty matches for the pattern are replaced when adjacent to a previous
- non-empty match.
+ An empty match can occur immediately after a non-empty match.
.. versionchanged:: 3.12
Group *id* can only contain ASCII digits.
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