Development guide#

This page provides procedures and guidelines for developing and contributing to Ook.

Scope of contributions#

Ook is an open source package, meaning that you can contribute to Ook itself, or fork Squarebot for your own purposes.

Since Ook is intended for internal use by Rubin Observatory, community contributions can only be accepted if they align with Rubin Observatory’s aims. For that reason, it’s a good idea to propose changes with a new GitHub issue before investing time in making a pull request.

Ook is developed by the Rubin Observatory SQuaRE team.

Setting up a local development environment#

Ook is a Python project that should be developed within a virtual environment. You can either manage this virtual environment yourself, or use nox -s venv-init to create one for you.

If you already have a Python virtual environment set up in your shell, you can use the nox -s init command to install Ook and its development dependencies into it:

git clone
cd ook
pip install nox
nox -s init

This init step does two things:

  1. Installs Ook along with its runtime and development dependencies.

  2. Installs the pre-commit hooks.

Nox can create the virtual environment for you and install Ook and its development dependencies init it:

git clone
cd ook
pip install nox
nox -s venv-init
source .venv/bin/activate

This init step does three things:

  1. Creates a venv virtual environment in the .venv subdirectory.

  2. Installs Ook along with its runtime and development dependencies.

  3. Installs the pre-commit hooks.

Whenever you return to the project in a new shell you will need to activate the virtual environment:

source .venv/bin/activate

Pre-commit hooks#

The pre-commit hooks, which are automatically installed by running the nox -s init-dev command on set up, ensure that files are valid and properly formatted. Some pre-commit hooks automatically reformat code:


Sorts Python imports and automatically fixes some common Python issues.


Automatically formats Python code.

When these hooks fail, your Git commit will be aborted. To proceed, stage the new modifications and proceed with your Git commit.

Running tests#

To test all components of Ook, run nox, which tests the library the same way that the GitHub Actions CI workflow does:


To see a listing of specific nox sessions, run:

nox -s

Building documentation#

Documentation is built with Sphinx:

nox -s docs

The build documentation is located in the docs/_build/html directory.

To check the documentation for broken links, run:

nox -s docs-linkcheck

Updating the change log#

Ook uses scriv to maintain its change log.

When preparing a pull request, run

nox -s scriv-create

This will create a change log fragment in changelog.d. Edit that fragment, removing the sections that do not apply and adding entries for your pull request.

Change log entries use the following sections:

  • Backward-incompatible changes

  • New features

  • Bug fixes

  • Other changes (for minor, patch-level changes that are not bug fixes, such as logging formatting changes or updates to the documentation)

Do not include a change log entry solely for updating pinned dependencies, without any visible change to Ook’s behavior. Every release is implicitly assumed to update all pinned dependencies.

These entries will eventually be cut and pasted into the release description for the next release, so the Markdown for the change descriptions must be compatible with GitHub’s Markdown conventions for the release description. Specifically:

  • Each bullet point should be entirely on one line, even if it contains multiple sentences. This is an exception to the normal documentation convention of a newline after each sentence. Unfortunately, GitHub interprets those newlines as hard line breaks, so they would result in an ugly release description.

  • Avoid using too much complex markup, such as nested bullet lists, since the formatting in the GitHub release description may not be what you expect and manually editing it is tedious.

Style guide#


  • The code style follows PEP 8, though in practice lean on Black and ruff to format the code for you. Use SQR-072 for for architectural guidance. Follow SQR-076 for the Pydantic-based Avro schemas.

  • Use PEP 484 type annotations. The nox -s typing test session, which runs mypy, ensures that the project’s types are consistent.

  • Write tests for Pytest.