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Python pre-commit Configuration: Black, isort, Flake8, and mypy

Configure Python pre-commit hooks with Black, isort, Flake8, and mypy to format code, sort imports, and check linting and types before each commit.

pre-commitgitblack

Git hooks are very useful tools that can be used in any project for many cases. Hooks can be run on every commit to verify the code, delete trailing spaces, run tests, etc. One of the tools which I’m using for it is pre-commit.

My favorite use case is checking the style and quality of Python code. It helps to do more detailed code reviews and focus on logic which is very important rather than pointing to the wrong import order.

  • black - very good Python formatter, having very limited configuration options to allow keep code in the same convention improving the readability
  • isort - library which helps with organizing imports alphabetically and segregate imports by type
  • flake8 - Python linter which includes tools like PyFlakes, pycodestyle, and Ned Batchelder’s McCabe script
  • mypy - static typing checker, helps to not forget about type annotations, this one is a little annoying sometimes so be careful with it

Instalation

  1. Install pre commit hook
pip install pre-commit
  1. Create a configuration in file pre-commit-config.yaml
repos:
 - repo: https://github.com/pre-commit/mirrors-mypy
    rev: v0.800
    hooks:
      - id: mypy
        args: [--no-strict-optional, --ignore-missing-imports]
        files: ^(app/|tests/)
  - repo: local
    hooks:
      - id: black
        name: black
        entry: black
        language: system
        types: [ python ]
        files: ^(app/|tests/)
      - id: isort
        name: isort
        entry: isort
        language: system
        types: [ python ]
        include: ^(app/|tests/)
        exclude: '.*/migrations/.*'
        args: [
            '--line-length=110',
            '--multi-line=3',
            '--force-grid-wrap=0',
            '--trailing-comma',
            '--use-parentheses',
            '--ensure-newline-before-comments',
        ]
      - id: flake8
        name: flake8
        entry: flake8
        language: system
        types: [ python ]
        files: ^(app/|tests/)
  1. Install git hook scripts
pre-commit install
  1. Run against all files
pre-commit run --all-files

Summary

Copy and paste the config and have fun! Remember that more tools can be used for the configurations. For more use cases please check this repository.

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