GeezerVison

The World Wide Web, restored to 800 pixels of glory.

GeezerVison is showing github.com — gh-86519: Add prefixmatch APIs to the re module by gpshead · Pull Request #31137 · python/cpython

Conversation

gpshead commented Feb 5, 2022 •

edited

Loading

Uh oh!

There was an error while loading. Please reload this page.

Copy link

Copy Markdown

Member

Adds prefixmatch APIs to the re module as an alternate name for our long existing match APIs to help alleviate a common Python confusion for those coming from other languages regular expression libraries.

These alleviate common confusion around what "match" means as Python is different than other popular languages regex libraries in our use of the term as an API name. The original match names are NOT being deprecated. Source tooling like linters, IDEs, and LLMs could suggest using prefixmatch instead of match to improve code health and reduce cognitive burden of understanding the intent of code when configured for a modern minimum Python version.

See the documentation changes for a better description.

Discussions took place in the PR, in the issue, and finally at https://discuss.python.org/t/add-re-prefixmatch-deprecate-re-match/105927

Issue: Proposal: re.prefixmatch method (alias for re.match) #86519

Documentation Preview: https://cpython-previews--31137.org.readthedocs.build/en/31137/

Sorry, something went wrong.

Uh oh!

There was an error while loading. Please reload this page.

hauntsaninja and hugovk reacted with thumbs up emoji

msuozzo reacted with hooray emoji

All reactions

👍 2 reactions
🎉 1 reaction


          bpo-42353: Add prefixmatch APIs to the re module.

587dc4d

These alleviate common confusion around what "match" means as Python is
different than other popular languages in our use of the term as an API
name.  The original "match" names are NOT being deprecated.  Source
tooling like linters are expected to suggest using prefixmatch instead
of match to improve code health and reduce cognitive burden of
understanding the intent when reading code.

See the documentation changes within this PR for a better description.

gpshead added the type-feature A feature request or enhancement label

Feb 5, 2022

the-knights-who-say-ni added the CLA signed label

Feb 5, 2022

bedevere-bot added the awaiting core review label

Feb 5, 2022

gpshead added the DO-NOT-MERGE label

Feb 17, 2022

gpshead mentioned this pull request

Jul 7, 2022

Proposal: re.prefixmatch method (alias for re.match) #86519

Closed

ezio-melotti removed the CLA signed label

Jul 13, 2022

gpshead marked this pull request as draft

January 30, 2023 05:20

gpshead changed the title ~~bpo-42353: Add prefixmatch APIs to the re module~~ gh-86519: Add prefixmatch APIs to the re module

Jan 30, 2023

gpshead added 3 commits

January 29, 2023 22:45


          Merge branch 'main' into prefixmatch-b42353

c7d1581


          fix editor fat finger typo during the merge. #vim

fa2885e


          3.12

6195ad7

gpshead removed the DO-NOT-MERGE label

Jan 30, 2023


          Merge branch 'main' into prefixmatch-b42353

0296f29

python-cla-bot Bot commented Apr 18, 2025 •

edited

Loading

Uh oh!

There was an error while loading. Please reload this page.

Copy link

Copy Markdown

All commit authors signed the Contributor License Agreement.

All reactions

Sorry, something went wrong.

Uh oh!

There was an error while loading. Please reload this page.


          Merge main and modernize the relevant docs.

bab8e8b

gpshead force-pushed the prefixmatch-b42353 branch 3 times, most recently from 554bb41 to 54c77ca Compare

April 19, 2025 01:09


          Simplify, don't have duplicate definitions.

149f6e4

`match = prefixmatch`

gpshead force-pushed the prefixmatch-b42353 branch from 54c77ca to 149f6e4 Compare

April 19, 2025 01:20

hugovk mentioned this pull request

Jan 30, 2026

FURB167: change example to re.search with ^ anchor astral-sh/ruff#22984

Merged

ntBre pushed a commit to astral-sh/ruff that referenced this pull request

Jan 30, 2026


          FURB167: change example to re.search with ^ anchor (#22984)

38d4f49

## Summary

The example for
[FURB167](https://docs.astral.sh/ruff/rules/regex-flag-alias/#regex-flag-alias-furb167)
has `re.match` with an `^` anchor to match the start of the string:

```python
if re.match("^hello", "hello world", re.I):
```

But `re.match` already implicitly matches the start of the string:

https://docs.python.org/3/library/re.html#search-vs-match

Let's change the example to `re.search` so the anchor isn't redundant.
(The anchor's actually irrelevant to the example for this rule about
long or short flag names.)

(Aside: There's a discussion about adding `re.prefixmatch` and [soft]
deprecating `re.match` because of the confusion around it:
https://discuss.python.org/t/add-re-prefixmatch-deprecate-re-match/105927,
python/cpython#86519,
python/cpython#31137.)



## Test Plan

<!-- How was it tested? -->

1. Create feature branch
2. Push to my fork to run CI
3. Realise feature branches are disabled for forks in Ruff CI
4. Merge feature branch to my `main`
5. Push that
6. Be happy I did, because it failed because I missed something
7. Fixup, pushup
8. Passes [🎉](https://github.com/hugovk/ruff/actions/runs/21524112749)

gpshead and others added 4 commits

January 31, 2026 15:18


          Merge main into prefixmatch-b42353

e176692

Resolved conflicts:
- Doc/whatsnew/3.14.rst: Used main's version (3.14 is released)
- Lib/re/__init__.py: Removed __version__ (removed in main), updated
  docstring to reference 3.15 instead of 3.14

Added prefixmatch What's New entry to Doc/whatsnew/3.15.rst since the
feature is now targeting Python 3.15.


          Update match name removal language to be definitive

58d8f57

- Change "25 years" to "30 years" to reflect actual time
- Replace speculative "this decade, if ever" / "7 years" language
  with clear statement that we will never remove the original
  match name

Co-Authored-By: Claude Opus 4.5 <[email protected]>


          Fix re.rst examples after match to search conversion

3cd9d71

- Fix traceback to include ^ anchor matching the pair pattern definition
- Add \A anchor to one example as a teaching hint for readers
- Update card game examples to demonstrate search/match/prefixmatch mix
- Add explanatory paragraph about match and prefixmatch being identical
- Rename compiled regex variables to use _re suffix (valid_hand_re, pair_re)

Co-Authored-By: Claude Opus 4.5 <[email protected]>


          Replace name-parsing examples with Monty Python references

d6090bb

Using first_name/last_name patterns promotes the myth that names
have simple, universal structures. Replace with:
- "killer rabbit" with adjective/animal groups
- "Norwegian Blue, pining for the fjords" for unlabeled groups

gpshead marked this pull request as ready for review

February 1, 2026 00:12

gpshead requested a review from AA-Turner as a code owner

February 1, 2026 00:12

hauntsaninja approved these changes

Feb 8, 2026

View reviewed changes

hauntsaninja left a comment

Copy link

Copy Markdown

Contributor

There was a problem hiding this comment.

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Great, thank you for making this happen!

Sorry, something went wrong.

Uh oh!

There was an error while loading. Please reload this page.

All reactions

Comment thread

Modules/_sre/sre.c Resolved

Uh oh!

There was an error while loading. Please reload this page.

bedevere-app Bot added awaiting merge and removed awaiting core review labels

Feb 8, 2026

hauntsaninja reviewed

Feb 8, 2026

View reviewed changes

Comment thread

Doc/library/re.rst Resolved

Uh oh!

There was an error while loading. Please reload this page.

picnixz commented Feb 8, 2026

Copy link

Copy Markdown

Member

Did we actually reached a consensus on DPO for that feature to be merged? I thought there were some issues, especially with the fact that regex needs to be updated to be with parity.

All reactions

Sorry, something went wrong.

Uh oh!

There was an error while loading. Please reload this page.

picnixz reviewed

Feb 8, 2026

View reviewed changes

Comment thread

Lib/test/test_re.py Resolved

Uh oh!

There was an error while loading. Please reload this page.

hugovk commented Feb 8, 2026

Copy link

Copy Markdown

Member

Did we actually reached a consensus on DPO for that feature to be merged?

Yes, I think the 24 hearts on Greg's https://discuss.python.org/t/add-re-prefixmatch-deprecate-re-match/105927/20 is a pretty good sign.

The only other posts with double-digit hearts are also in support: the OP (10), a docs suggestion from Tim (14), a name suggestion (startswith) from Marc-André (11).

I thought there were some issues, especially with the fact that regex needs to be updated to be with parity.

Whatever the third-party regex package does or doesn't do, shouldn't hold us back. They say "This regex implementation is backwards-compatible with the standard ‘re’ module, but offers additional functionality", so it doesn't sound like it'll be a problem for them to do the same thing.

gpshead reacted with heart emoji

All reactions

❤️ 1 reaction

Sorry, something went wrong.

Uh oh!

There was an error while loading. Please reload this page.

hugovk approved these changes

Feb 8, 2026

View reviewed changes

hugovk left a comment

Copy link

Copy Markdown

Member

There was a problem hiding this comment.

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Thanks!

Non-blocking docs suggestion:

Use prefixmatch pretty much throughout, except to mention match is the alias (plus version changed etc.), which you've mostly already done here.

We can also update other places like the regex HOWTO to prefer the new name, but this can also be in a followup.

Bike shed colour:

I'm fine with either prefixmatch and startswith.

Pro for prefixmatch: it keeps the "match" part, which might help remind people when they see match: "oh, wait, is this the lopsided prefixmatch or fullmatch? I'd better double check the docs and use one of those descriptive names or instead search with explicit anchors."

Soft deprecation:

We're discouraging in docs and not planning on removing. Sounds like soft deprecation. I'd be fine with soft deprecating too, but that could also be another discussion once this is done (if anyone has energy for that!).

Sorry, something went wrong.

Uh oh!

There was an error while loading. Please reload this page.

There was an error while loading. Please reload this page.

picnixz requested a review from serhiy-storchaka

February 8, 2026 21:59

gpshead commented Feb 8, 2026

Copy link

Copy Markdown

Member Author

Bike shed colour:
I'm fine with either prefixmatch and startswith.
Pro for prefixmatch: it keeps the "match" part, which might help remind people

I'm similarly inclined to stick with prefixmatch. It ties in with match wording elsewhere and avoids confusion w.r.t. the str/bytes methods of the same startswith name.

lots of what look like good comments on the docs here and thoughts on how to document this to digest from the discuss thread. i'll work on getting the doc edits in and see if it looks like it needs more review after that.

hauntsaninja and hugovk reacted with thumbs up emoji

All reactions

👍 2 reactions

Sorry, something went wrong.

Uh oh!

There was an error while loading. Please reload this page.

gpshead and others added 8 commits

February 9, 2026 00:05


          Address reviewer docs feedback: prefer prefixmatch throughout

341972f

Apply suggestions from hugovk and hauntsaninja reviews:
- List prefixmatch before match in function/method signatures
- Use prefixmatch exclusively in examples, remove redundant match duplicates
- Remove interchangeable paragraph (covered by prefixmatch-vs-match section)
- Rename section to "search() vs. prefixmatch()"
- Add .. note:: directive for MULTILINE caveat
- Fix time-sensitive wording ("very recent Python", "never")
- Fix alphabetical ordering in whatsnew/3.15.rst
- Fix comment grammar in Lib/re/__init__.py

Co-Authored-By: Claude Opus 4.6 <[email protected]>


          Statically alias match to prefixmatch instead of runtime memcpy

cd8d85d

Replace the copy_prefixmatch_method_def_to_match() runtime memcpy with
static struct initializers that reuse the Clinic-generated prefixmatch
parser directly. This avoids duplicating argument parsing boilerplate
while keeping everything initialized at compile time.

Add Py_DEBUG assertions in sre_exec to verify the match and prefixmatch
method table entries remain identical except for ml_name.

Co-Authored-By: Claude Opus 4.6 <[email protected]>


          Merge main into prefixmatch-b42353

74d51b3


          Fix whatsnew 3.15 RST heading that matches git conflict marker

4abdff0

The "Removed" heading underline was exactly 7 '=' characters, which
triggers the check-merge-conflict pre-commit hook as a false positive.

Co-Authored-By: Claude Opus 4.6 <[email protected]>


          docs, remove errant "if ever"

6bacfb0


          doc wording tweaks jf clarity

40e6a2a


          Extract do_test_match_getitem helper to preserve git blame

b3c6948

Refactor test_match_getitem to use a helper method instead of a
for loop, keeping the assertion lines at their original indentation
to preserve git line attribution history.

Co-Authored-By: Claude Opus 4.6 <[email protected]>


          tweak news to match docs

b277981

gpshead self-assigned this

Feb 9, 2026

gpshead merged commit 300de1e into python:main

Feb 16, 2026

50 checks passed

Uh oh!

There was an error while loading. Please reload this page.

bedevere-app Bot removed the awaiting merge label

Feb 16, 2026

gpshead commented Feb 16, 2026

Copy link

Copy Markdown

Member Author

merged, thanks for everyones reviews and discussions!

hugovk reacted with rocket emoji

All reactions

🚀 1 reaction

Sorry, something went wrong.

Uh oh!

There was an error while loading. Please reload this page.

gpshead mentioned this pull request

Feb 16, 2026

Add an explicit prefixmatch API name for match for parity CPython 3.15 mrabarnett/mrab-regex#601

Closed

brijkapadia pushed a commit to brijkapadia/cpython that referenced this pull request

Feb 28, 2026


          pythongh-86519: Add prefixmatch APIs to the re module (pythonGH-31137)

22df6fe

Adds `prefixmatch` APIs to the re module as an alternate name for our long existing `match` APIs to help alleviate a common Python confusion for those coming from other languages regular expression libraries.

These alleviate common confusion around what "match" means as Python is different than other popular languages regex libraries in our use of the term as an API name.  The original `match` names are **NOT being deprecated**.  Source tooling like linters, IDEs, and LLMs could suggest using `prefixmatch` instead of match to improve code health and reduce cognitive burden of understanding the intent of code when configured for a modern minimum Python version.

See the documentation changes for a better description.

Discussions took place in the PR, in the issue, and finally at https://discuss.python.org/t/add-re-prefixmatch-deprecate-re-match/105927

Co-Authored-By: Claude Opus 4.5 <[email protected]>
Co-authored-by: Shantanu <[email protected]>
Co-Authored-By: Claude Opus 4.6 <[email protected]>

vstinner mentioned this pull request

Mar 18, 2026

Update test_validators.py for Python 3.15a7 python-attrs/attrs#1530

Merged

3 of 12 tasks

hugovk commented Apr 4, 2026

Copy link

Copy Markdown

Member

We can also update other places like the regex HOWTO to prefer the new name, but this can also be in a followup.

Please see PR #148096.

All reactions

Sorry, something went wrong.

Uh oh!

There was an error while loading. Please reload this page.

hugovk mentioned this pull request

Apr 4, 2026

Soft deprecate re.match and re.Pattern.match in favour of prefixmatch #148100

Closed

ljfp pushed a commit to ljfp/cpython that referenced this pull request

Apr 25, 2026


          pythongh-86519: Add prefixmatch APIs to the re module (pythonGH-31137)

a8c1cbc

Adds `prefixmatch` APIs to the re module as an alternate name for our long existing `match` APIs to help alleviate a common Python confusion for those coming from other languages regular expression libraries.

These alleviate common confusion around what "match" means as Python is different than other popular languages regex libraries in our use of the term as an API name.  The original `match` names are **NOT being deprecated**.  Source tooling like linters, IDEs, and LLMs could suggest using `prefixmatch` instead of match to improve code health and reduce cognitive burden of understanding the intent of code when configured for a modern minimum Python version.

See the documentation changes for a better description.

Discussions took place in the PR, in the issue, and finally at https://discuss.python.org/t/add-re-prefixmatch-deprecate-re-match/105927

Co-Authored-By: Claude Opus 4.5 <[email protected]>
Co-authored-by: Shantanu <[email protected]>
Co-Authored-By: Claude Opus 4.6 <[email protected]>

KotlinIsland pushed a commit to KotlinIsland/basedpython that referenced this pull request

May 1, 2026


          FURB167: change example to re.search with ^ anchor (#22984)

730e469

## Summary

The example for
[FURB167](https://docs.astral.sh/ruff/rules/regex-flag-alias/#regex-flag-alias-furb167)
has `re.match` with an `^` anchor to match the start of the string:

```python
if re.match("^hello", "hello world", re.I):
```

But `re.match` already implicitly matches the start of the string:

https://docs.python.org/3/library/re.html#search-vs-match

Let's change the example to `re.search` so the anchor isn't redundant.
(The anchor's actually irrelevant to the example for this rule about
long or short flag names.)

(Aside: There's a discussion about adding `re.prefixmatch` and [soft]
deprecating `re.match` because of the confusion around it:
https://discuss.python.org/t/add-re-prefixmatch-deprecate-re-match/105927,
python/cpython#86519,
python/cpython#31137.)



## Test Plan

<!-- How was it tested? -->

1. Create feature branch
2. Push to my fork to run CI
3. Realise feature branches are disabled for forks in Ruff CI
4. Merge feature branch to my `main`
5. Push that
6. Be happy I did, because it failed because I missed something
7. Fixup, pushup
8. Passes [🎉](https://github.com/hugovk/ruff/actions/runs/21524112749)

samhaese mentioned this pull request

Jun 2, 2026

(skip issue) Respect Isaac Newton and Malcolm Reynolds by reverting their removal in #31137 #150807

Closed

decorator-factory added a commit to decorator-factory/python-re-quiz that referenced this pull request

Aug 8, 2026


          Acknowledge the match -> prefixmatch change

9d8f49d

See python/cpython#31137 for more details

Reviewers

picnixz

picnixz left review comments

hauntsaninja

hauntsaninja approved these changes

hugovk

hugovk approved these changes

AA-Turner

Awaiting requested review from AA-Turner

AA-Turner is a code owner

serhiy-storchaka

Awaiting requested review from serhiy-storchaka

Uh oh!

There was an error while loading. Please reload this page.

Assignees

gpshead

Labels

type-feature

A feature request or enhancement

Projects

None yet

Milestone

No milestone

Development

Successfully merging this pull request may close these issues.

Uh oh!

There was an error while loading. Please reload this page.

7 participants

Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.

You are visitor 01402503 — GeezerVison does not store the pages you look up.
Best viewed with Netscape Navigator 4.7 or Internet Explorer 6 at 800×600. No cookies required.

GeezerVison

Conversation

gpshead commented Feb 5, 2022 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

python-cla-bot Bot commented Apr 18, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

hauntsaninja left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

picnixz commented Feb 8, 2026

Uh oh!

Uh oh!

hugovk commented Feb 8, 2026

Uh oh!

hugovk left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

gpshead commented Feb 8, 2026

Uh oh!

Uh oh!

gpshead commented Feb 16, 2026

Uh oh!

hugovk commented Apr 4, 2026

Uh oh!

Reviewers

Uh oh!

Assignees

Labels

Projects

Milestone

Development

Uh oh!

7 participants

gpshead commented Feb 5, 2022 •

edited

Loading

Uh oh!

There was an error while loading. Please reload this page.

python-cla-bot Bot commented Apr 18, 2025 •

edited

Loading

Uh oh!

There was an error while loading. Please reload this page.