Configure pre-commit with black, flake8, and pre-commit hooks

To run black code formatter, flake8 linter, as well as other hooks (e.g., pretty-format-json) automatically each time something is committed to a repo:

1. Install pre-commit on the local computer (in macOS can use brew install pre-commit, in linux can install in a virtualenv using pip install pre-commit)

2. Add a .pre-commit-config.yaml to the root of the repository:

   repos:
     - repo: https://github.com/pre-commit/pre-commit-hooks
       rev: v3.4.0
       hooks:
         - id: check-json
         - id: pretty-format-json
           args: [--no-sort-keys, --autofix, --no-ensure-ascii ]
   
     - repo: https://github.com/ambv/black
       rev: 20.8b1
       hooks:
         - id: black
           language_version: python3
     - repo: https://gitlab.com/pycqa/flake8
       rev: 3.8.4
       hooks:
         - id: flake8
   

3. Add a pyproject.toml file for black configuration:

   [tool.black]
   line-length = 88
   include = '\.pyi?$'
   exclude = '''
   /(
       \.git
     | \.hg
     | \.mypy_cache
     | \.tox
     | \.venv
     | _build
     | buck-out
     | build
     | dist
   )/
   '''
   

4. Add a .flake8 configuration file:

   [flake8]
   ignore = E203, E266, E501, W503, F403, F401
   max-line-length = 88
   max-complexity = 18
   select = B,C,E,F,W,T4,B9
   

5. Install git hooks in the repository .git/ directory:

   > pre-commit install
   

References

1. pre-commit (pre-commit.com)
2. Automate Python workflow using pre-commits: black and flake8 (ljvmiranda921.github.io)
3. How to setup your project with pre-commit, black, and flake8 (dev.to)
4. Where does pre-commit install “environments”? (stackoverflow.com)