Title: Replace empty matches adjacent to a previous non-empty match in re.sub()
Type: enhancement Stage: resolved
Components: Library (Lib), Regular Expressions Versions: Python 3.7
Status: closed Resolution: fixed
Dependencies: Superseder:
Assigned To: serhiy.storchaka Nosy List: ezio.melotti, mrabarnett, serhiy.storchaka
Priority: normal Keywords: patch

Created on 2017-12-13 18:28 by serhiy.storchaka, last changed 2018-01-04 09:06 by serhiy.storchaka. This issue is now closed.

Pull Requests
URL Status Linked Edit
PR 4846 merged serhiy.storchaka, 2017-12-13 18:34
Messages (3)
msg308229 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2017-12-13 18:28
Currently re.sub() replaces empty matches only when not adjacent to a previous match. This makes it inconsistent with re.findall() and re.finditer() which finds empty matches adjacent to a previous non-empty match and with other RE engines.

Proposed PR makes all functions that makes repeated searching (re.split(), re.sub(), re.findall(), re.finditer()) mutually consistent.

The PR change the behavior of re.split() too, but this doesn't matter, since it already is different from the 3.6 behavior.

BDFL have approved this change.

This change doesn't break any stdlib code. It is expected that it will not break much third-party code, and even if it will break some code, it can be easily rewritten. For example replacing re.sub('(.*)', ...) (which now matches an empty string at the end of the string) with re.sub('(.+)', ...) is an obvious fix.
msg309055 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2017-12-26 10:14
Could anybody please make a review of at least the documentation part?
msg309458 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2018-01-04 09:06
New changeset fbb490fd2f38bd817d99c20c05121ad0168a38ee by Serhiy Storchaka in branch 'master':
bpo-32308: Replace empty matches adjacent to a previous non-empty match in re.sub(). (#4846)
Date User Action Args
2018-01-04 09:06:40serhiy.storchakasetstatus: open -> closed
resolution: fixed
stage: patch review -> resolved
2018-01-04 09:06:15serhiy.storchakasetmessages: + msg309458
2017-12-26 10:14:59serhiy.storchakasetmessages: + msg309055
2017-12-13 18:34:24serhiy.storchakasetkeywords: + patch
stage: patch review
pull_requests: + pull_request4734
2017-12-13 18:28:38serhiy.storchakacreate