From 3690587c95084a2d6aebf97eb8d0525c5201c874 Mon Sep 17 00:00:00 2001 From: Serhiy Storchaka Date: Mon, 19 May 2025 16:27:50 +0300 Subject: [PATCH] gh-122055: Clarify documentation for empty matches in RE (GH-133169) (cherry picked from commit 44b73d3cd4466e148460883acf4494124eae8c91) Co-authored-by: Serhiy Storchaka --- Doc/library/re.rst | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) 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.