## Development Environment FAQ

### How to maintain `requirements.txt`?

The canonical list of installation requirements (including development requirements) is maintained in the [`setup.py`](setup.py) file.

The Requirements File ([`requirements.txt`](requirements.txt)) file must be kept in sync with that list.

To to automatically generate or update `requirements.txt` based on `setup.py`, run [`pip-tools`](https://github.com/jazzband/pip-tools)’s `pip-compile`:

```sh
python -m piptools compile --output-file=requirements.txt
```

**Warning:** Due to [limitations](https://github.com/jazzband/pip-tools/issues/908) in `pip-tools`, the same workflow can not be used for generating a `dev-requirements.txt` file, and requirements can not be declared in a `setup.cfg` file.

### How to install modules required for development?

```sh
python -m pip install -e ".[dev]"
```

### How to run a code formatter?

Run [Black](https://black.readthedocs.io/):

```sh
# Dry-run, showing what should be rewritten:
python -m black --target-version=py36 --diff .

# Run code format:
python -m black --target-version=py36 .
```

### How to run a linter?

Run [Flake8](https://flake8.pycqa.org/):

```sh
python -m flake8
```