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GeezerVison is showing github.com — gh-153568: Don't materialize parser token text that is never read by pablogsal · Pull Request #153576 · python/cpython

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@pablogsal

@pablogsal pablogsal commented Jul 11, 2026 •
edited by bedevere-app Bot
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The parser created a bytes object for every token, but only identifiers, keywords, numbers, strings and type comments ever have their text read. Operators and structural tokens now skip the allocation entirely.

Benchmark (parsing 8 of the largest stdlib files, 1.3 MB, 20 times per run with _PyParser_ASTFromString — parser only, no AST-to-Python conversion; pyperf, interleaved runs):

build time per run speedup
main 1.72 s ± 0.04
this PR 1.69 s ± 0.03 1.02x faster
  • Issue: Speed up the parser #153568

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@pablogsal
pablogsal requested a review from lysnikolaou as a code owner July 11, 2026 14:07
@bedevere-app bedevere-app Bot mentioned this pull request Jul 11, 2026
Speed up the parser #153568
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@bedevere-app bedevere-app Bot added the awaiting core review label Jul 11, 2026
maurycy
maurycy reviewed Jul 11, 2026
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Comment thread Parser/pegen.c Resolved

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@maurycy

maurycy commented Jul 19, 2026 •
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It seems that 1e18605, suggested by me, broke a lot! I think it means that token_type == NAME is mapped to something that's not in the token_needs_text(). I did not understand this. This is fragile! My bad.
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@pablogsal
pablogsal force-pushed the gh-153568-token-text branch 2 times, most recently from 382cb01 to f78606c Compare August 27, 2026 11:39
pablogsal and others added 3 commits September 14, 2026 16:32
@pablogsal
pythongh-153568: Don't materialize parser token text that is never read
36ece16 
Only tokens whose text is actually consumed get a bytes object;
operators and structural tokens no longer allocate one.
@pablogsal @maurycy
Update Parser/pegen.c
0e3cfae 
Co-authored-by: Maurycy Pawłowski-Wieroński <[email protected]>
@pablogsal
pythongh-153568: Preserve keyword token text
3a71cad
@pablogsal
pablogsal force-pushed the gh-153568-token-text branch from f78606c to 3a71cad Compare September 14, 2026 15:34
@pablogsal
pablogsal enabled auto-merge (squash) September 14, 2026 20:27
@pablogsal
pablogsal merged commit e5fbabb into python:main Sep 14, 2026
98 of 100 checks passed

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@pablogsal
pablogsal deleted the gh-153568-token-text branch September 14, 2026 20:32
@bedevere-app bedevere-app Bot removed the awaiting core review label Sep 14, 2026
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@lysnikolaou lysnikolaou Awaiting requested review from lysnikolaou lysnikolaou is a code owner
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@maurycy maurycy maurycy left review comments
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2 participants

@pablogsal @maurycy
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