GV

GeezerVison

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

Home|About|Gaming cabinet|Archives|How it works|Starter sites

On this site

  • Sign in
  • ActionsCI/CD and automation
  • CodespacesCloud development environments
  • All Features
  • Documentation
  • Training
  • Certifications
  • Build with Copilot
  • Customize Copilot
  • Integrations
  • Trending repos
  • GitHub Sponsors
  • Developer articles
  • Enterprises

This view

  • Original page
  • New address

GeezerVison is showing github.com — gh-153568: Skip PEG alternatives that cannot match the next token by lysnikolaou · Pull Request #160458 · python/cpython

Conversation

@lysnikolaou

@lysnikolaou lysnikolaou commented Oct 23, 2026 •
edited by bedevere-app Bot
Loading

Uh oh!

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

Copy link
Copy Markdown
Member

Rules with several alternatives now switch on the next token's type and only try the alternatives that may start with it. Loops stop as soon as the next token cannot start another iteration. Both use FIRST sets from a new analysis, which also replaces the old first_sets.py calculator.

  • Issue: Speed up the parser #153568

Sorry, something went wrong.

Uh oh!

There was an error while loading. Please reload this page.
All reactions
@lysnikolaou @pablogsal
pythongh-153568: Skip PEG alternatives that cannot match the next token
cba604e 
Rules with several alternatives now switch on the next token's type and
only try the alternatives that may start with it. Loops stop as soon as
the next token cannot start another iteration. Both use FIRST sets from
a new analysis, which also replaces the old first_sets.py calculator.

Co-authored-by: Pablo Galindo <[email protected]>
@lysnikolaou
lysnikolaou requested a review from pablogsal as a code owner October 23, 2026 18:10
@bedevere-app bedevere-app Bot added awaiting core review type-feature A feature request or enhancement labels Oct 23, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Oct 23, 2026
Speed up the parser #153568
Open
@lysnikolaou
Merge remote-tracking branch 'upstream/main' into pegen-first-set-dis…
d60946f 
…patch
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@pablogsal pablogsal Awaiting requested review from pablogsal pablogsal is a code owner

Uh oh!

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

Assignees

No one assigned

Labels

awaiting core review 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.

1 participant

@lysnikolaou
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.