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Speed up _is_eol_token #1256

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Speed up _is_eol_token #1256

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correctmost
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This change provides a small speed-up on large codebases (~200ms).

Stats

Before

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
  1478156    0.940    0.000    1.245    0.000 pycodestyle.py:1831(_is_eol_token)
  1472360    0.359    0.000    0.359    0.000 {method 'lstrip' of 'str' objects}
Command Mean [s] Min [s] Max [s] Relative
pycodestyle . 18.349 ± 0.161 18.119 18.641 1.00

After

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
  1478156    0.458    0.000    0.459    0.000 pycodestyle.py:1831(_is_eol_token)
   225341    0.057    0.000    0.057    0.000 {method 'lstrip' of 'str' objects}
Command Mean [s] Min [s] Max [s] Relative
pycodestyle . 18.145 ± 0.098 17.997 18.283 1.00

Set-up

I profiled pycodestyle with the yt-dlp codebase because it is similar in composition to a private codebase I have.

git clone https://github.com/yt-dlp/yt-dlp.git
cd yt-dlp

git checkout ef36d517f9b05785d61abca7691d9ab7d63cc75c

# Callgraph command
python -m cProfile -o stats $(which pycodestyle)

# Benchmarking command
hyperfine --ignore-failure --warmup 2 --runs 15 --export-markdown=baseline.md 'pycodestyle .'

setup.cfg

[pycodestyle]
ignore = W504
max-line-length = 100

Baseline version: c8e36a0

correctmost
correctmost commented Aug 10, 2024
View reviewed changes
pycodestyle.py

# Check if the line's penultimate character is a continuation
# character
if token[4][-2] != '\\':
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Based on local testing with Python 3.12.4, I had assumed that the string length would always be >=2 here.

It looks like that is not the case with all supported versions of Python.

@correctmost
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Closing because this approach doesn't work for all Python versions.

@correctmost
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I updated the patch and re-ran the benchmarks.

The additional tokenize.ENDMARKER check seems to have reduced the savings from ~200ms to ~100ms.

If this PR seems too risky because of assumptions about tokenization, feel free to pass on it :).

Stats

Before

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
  1478156    0.885    0.000    1.197    0.000 pycodestyle.py:1831(_is_eol_token)
  1472360    0.364    0.000    0.364    0.000 {method 'lstrip' of 'str' objects}
Command Mean [s] Min [s] Max [s] Relative
pycodestyle . 18.472 ± 0.196 18.067 18.848 1.00

After

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
  1478156    0.511    0.000    0.511    0.000 pycodestyle.py:1831(_is_eol_token)
   225341    0.055    0.000    0.055    0.000 {method 'lstrip' of 'str' objects}
Command Mean [s] Min [s] Max [s] Relative
pycodestyle . 18.360 ± 0.186 18.159 18.781 1.00

@correctmost correctmost mentioned this pull request Aug 10, 2024
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