pre-commit implementation notes

In this article, we will explain how to introduce and utilize pre-commit, a tool that automatically formats and checks code and documents before committing to Git.

Introduction: What is pre-commit?

pre-commit is a Python tool for easily managing and operating Git’s “pre-commit hooks”. You can automate tasks such as:

• Line break check at end of file

• Formatting Python code (Black)

• Markdown and reStructuredText grammar check

• YAML/JSON/TOML syntax checking

• Detection of security-risky code (e.g. Bandit)

Installation and initial configuration

First, install pre-commit. It can be used in a virtual environment or the entire system.

pip install pre-commit

Or if you’re a pipx fan:

pipx install pre-commit

Next, create .pre-commit-config.yaml at the root of your project.

Basic example:

repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
      - id: end-of-file-fixer
      - id: trailing-whitespace

  - repo: https://github.com/psf/black
    rev: 24.3.0
    hooks:
      - id: black

  - repo: https://github.com/pycqa/flake8
    rev: 6.1.0
    hooks:
      - id: flake8

Installing the hook:

pre-commit install

This will automatically run the check on your next git commit.

Version control and automatic updates

All hooks have a version (rev) specified and can be updated in bulk with the following command:

pre-commit autoupdate

Document checking with pre-commit

Lightweight markup like Markdown and reStructuredText can also be maintained with pre-commit.

• doctoc: Markdown table of contents automatic generation

• mdformat: Automatic formatting of Markdown (made in Python)

• doc8: reStructuredText rule check

• rstcheck: Syntax validation for Sphinx

If you use pre-commit to automatically generate a table of contents and format API documentation, the big advantage is that you can prevent documents from becoming obsolete while also being able to show them as differences.

If you want to check all files, use the following command:

pre-commit run --all-files

Since pre-commit automatically performs format corrections, etc., files may be changed unintentionally. In that case, you can revert to the most recent commit with the following command:

git restore --source=HEAD --staged --worktree .

Thorough pre-commit

The hook runs on every commit, which has the following effects:

• Quality maintenance is guaranteed “automatically”

• Unification of Lint/formatting rules is forced

• Detect problems locally before CI notices them

If you are working with a team, clearly stating the following in your README or CONTRIBUTING will help make it more established:

pre-commit install

summary

We have organized the basics of implementation regarding pre-commit. In the future, we would like to consider comprehensive settings and collaboration with CI.

Article information

Post date:

2025-05-16

author:

Mr. Takagi

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