Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?

Latest commit


Git stats


Failed to load latest commit information.
Latest commit message
Commit time

Build Status Coverage status


Everything flake8 used to do (by accident), plus much more.

A tool and pre-commit hook to lint Cython files.

Used by

Here's some major projects using cython-lint - is yours missing? Feel free to open a pull request!

In addition:


$ pip install cython-lint

Usage as a pre-commit hook

See pre-commit for instructions

Sample .pre-commit-config.yaml:

-   repo:
    rev: v0.15.0
    -   id: cython-lint
    -   id: double-quote-cython-strings

Command-line example

$ cython-lint my_file_1.pyx my_file_2.pyx
my_file_1.pyx:54:5: 'get_conversion_factor' imported but unused
my_file_2.pyx:1112:38: 'mod' defined but unused (try prefixing with underscore?)
my_file_3.pyx:4:9: dangerous default value!
my_file_3.pyx:5:9: comma after base type in definition


The following configuration options are available:

  • exclude lines by including a # no-cython-lint comment (analogous to # noqa in flake8);

as well as the following command-line arguments:

  • --max-line-length to control the maximum line length used by pycodestyle;
  • --no-pycodestyle if you don't want the pycodestyle checks;
  • --ignore if you want to ignore some specific pycodestyle checks;
  • --files to pass a Regex pattern with which to match files to include;
  • --exclude to pass a Regex pattern with which to match files to exclude.

Configuration can be set project-wise in a pyproject.toml file at the root of the project. Here's an example pyproject.toml:

max-line-length = 88
ignore = ['E503', 'E504']
exclude = 'my_project/excluded_cython_file.pyx'

Which checks are implemented?

  • assert statement with tuple condition (always true...)
  • comma after base type definition (e.g. cdef ndarray, arr)
  • comparison between constants
  • dangerous default value
  • dict key repeated
  • dict key variable repeated
  • f-string without placeholders
  • if-statement with tuple condition (always true...)
  • late-binding closures
  • pointless string statement
  • pycodestyle nitpicks (which you can turn off with --no-pycodestyle)
  • repeated element in set
  • .strip, .rstrip, or .lstrip used with repeated characters
  • unnecessary list index lookup
  • unnecessary import alias
  • variable defined but unused
  • variable imported but unused

In addition, the following automated fixers are implemented:

  • double-quote-cython-strings (replace single quotes with double quotes, like the black formatter does)

More to come! Requests welcome!