A hallmark of clean code is consistent formatting, which becomes important when collaborating in a team. While manually using formatters or linters to check code is possible, it’s easy to forget. A more effective approach is to use tools like pre-commit hooks for automated code inspection before committing

The code in this post is available here.

# Formatting and Linting

Before delving into pre-commit hooks, let’s first examine the tools we’ll be utilizing. black is a widely employed Python code formatter that essentially adheres to PEP 8 and can swiftly reformat your code. One potential drawback of black is that it may convert the entire codebase to its own style. However, in most cases, it proves to be a valuable tool for maintaining consistent formatting.

After installing black by pip or by a package manger, you can easily run it on a Python file or an entire folder using the following command. The file(s) will be reformatted if no syntax errors are detected.

$ black <file_or_folder>

The Python linter introduced in this post is ruff, which is a relatively new tool compared to other linters like pylint or flake8, but it distinguishes itself with its speed. To execute ruff on the specified files or directories (after you installed it), use the following command:

$ ruff check <file_or_folder>

If a linting error can be automatically fixed by ruff, you can use the --fix flag to correct it:

$ ruff check --fix <file_or_folder>

To customize the linting rules, ruff can be configured using a pyproject.toml, ruff.toml, or .ruff.toml file. For example, if you have a function that returns a very long string, which violates the line length limit, you can add the following configuration to the pyproject.toml file to disable the error.

def get_long_string() -> str:
    # This is just an example; in real code, you can
    # use / or parentheses to break a long string.
    return "1231231231231231231231231231231231231231231231231231231231231231231231231222222222"

ignore = ["E501"]

# Installing pre-commit Hooks

pre-commit can be also installed using pip or a package manager. After installation, you can create a .pre-commit-config.yaml configuration file. Here’s an example that utilizes black and ruff to check Python files.

repos:
  - repo: https://github.com/psf/black
    # Black version.
    rev: 23.3.0
    hooks:
      - id: black
        language_version: python3

  - repo: https://github.com/astral-sh/ruff-pre-commit
    # Ruff version.
    rev: v0.0.278
    hooks:
      - id: ruff

To install the pre-commit hooks, run the following command:

$ pre-commit install

Once installed, pre-commit hooks will execute prior to each commit. If any of the hooks encounter an issue, the commit will be canceled, and an error message will appear.

# Learn More

• The Black code style
• Configuring Ruff. A detailed explanation of the configuration options.