Chromium Python Style Guide

For other languages, please see the Chromium style guides.

Chromium follows PEP-8.

It is also encouraged to follow advice from Google's Python Style Guide, which is a superset of PEP-8.

See also:

Our Previous Python Style

Chromium used to differ from PEP-8 in the following ways:

  • Use two-space indentation instead of four-space indentation.
  • Use CamelCase() method and function names instead of unix_hacker_style() names.
  • 80 character line limits rather than 79.

New scripts should not follow these deviations, but they should be followed when making changes to files that follow them.

Making Style Guide Changes

You can propose changes to this style guide by sending an email to Ideally, the list will arrive at some consensus and you can request review for a change to this file. If there's no consensus, //styleguide/python/OWNERS get to decide.



Depot tools contains a local copy of pylint, appropriately configured.

  • Directories need to opt into pylint presumbit checks via: input_api.canned_checks.RunPylint().


YAPF is the Python formatter used by:

git cl format --python

Directories can opt into enforcing auto-formatting by adding a .style.yapf file with the following contents:

based_on_style = pep8

Entire files can be formatted (rather than just touched lines) via:

git cl format --python --full

YAPF has gotchas. You should review its changes before submitting. Notably:

  • It does not re-wrap comments.
  • It won't insert characters in order wrap lines. You might need to add ()s yourself in order to have to wrap long lines for you.
  • It formats lists differently depending on whether or not they end with a trailing comma.


Editor Integration