How to build GitHub action for Python static check

This is a note about what I did to build a CI pipeline on GitHub action for Python static check.

Photo by Kat Damant on Unsplash

Background

Recently, I’ve been working on an existing Python project. There are test codes with pytestand some type checks with mypy . However, there are missing Lints because the engineers use PyCharm and it automatically tweaks the codes based on its settings. I usually use Vim as my editor and write Ruby, JavasScript, and Python. So I decided to build GitHub action static checks like type and lint to develop the service safely and continuously.

What I did

First of all, I researched the popular lint library for Python and picked up Ruff. There are provided settings officially.

GitHub - astral-sh/ruff: An extremely fast Python linter and code formatter, written in Rust.

But I created the workflow file by myself because it’s not difficult to set up and I usually try to keep the control as much as possible. The following YAML file is the workflow content.

name: Lint

on: [push]

jobs:
  ruff:
    runs-on: ubuntu-latest
    name: Lint with Ruff
    steps:
    - uses: actions/checkout@v4
    - name: Set up Python 3.9
      uses: actions/setup-python@v5
      with:
        python-version: 3.9
    - name: Install Ruff
      run: pip install ruff
    - name: Run Ruff
      run: ruff check --output-format=github src/

It works fine without the --output-format=github option. I added the option as reading the documents

Configuring Ruff - Ruff

I also added mypy check to the GitHub action like below.

name: Type check

on: [push]

jobs:
  mypy:
    runs-on: ubuntu-latest
    name: Type check with mypy
    steps:
    - uses: actions/checkout@v4
    - name: Set up Python 3.9
      uses: actions/setup-python@v5
      with:
        python-version: 3.9
    - name: Install Dependencies
      run: |
        pip install -r requirements.txt
    - name: Run mypy
      run: |
        MYPYPATH=src mypy --disallow-untyped-defs --namespace-packages --explicit-package-bases src

I think there would be disagreement with installing the libraries. I found articles saying the imported libraries can be ignored using the ignore_missing_imports option because they are out side of the service.

The mypy configuration file - mypy 1.11.0 documentation

I can see their point but I checked some OSS project made by python and realized it’s quite common to have types in the OSS projects. I checked a few OSS randomly and all of them used the types. So I decided not to use ignore_missing_imports option and added #type ignored to the import line respectively if it doesn’t support type.

That’s it!