Contributing

We'd love for you to contribute to py_ballisticcalc!

Issues¶

Questions, feature requests and bug reports are all welcome as discussions or issues.

To make it as simple as possible for us to help you, please include the output of the following call in your issue:

python -c "from importlib.metadata import metadata; print(metadata('py-ballisticcalc')['Version'])"

Please try to always include the above unless you're unable to install py-ballisticcalc or know it's not relevant to your question or feature request.

Pull Requests¶

It should be extremely simple to get started and create a Pull Request. py-ballisticcalc is released regularly so you should see your improvements release in a matter of days or weeks 🚀.

Unless your change is trivial (typo, docs tweak etc.), please create an issue to discuss the change before creating a pull request.

If you're looking for something to get your teeth into, check out the "help wanted" label on github.

To make contributing as easy and fast as possible, you'll want to run tests and linting locally. Luckily, py-ballisticcalc has few dependencies, and tests don't need access to databases, etc. Because of this, setting up and running the tests should be very simple.

Note

For high performance, the py-ballisticcalc.exts subproject requires cython to create compiled calculation engines.

Prerequisites¶

You'll need the following prerequisites:

Any Python version >= Python 3.10
venv or uv or other virtual environment tool
git

Installation and setup¶

Fork the repository on GitHub and clone your fork locally.

# Clone your fork and cd into the repo directory
git clone git@github.com:<your username>/py-ballisticcalc.git
cd py-ballisticcalc

pipuv

# Setup virtual environment (we will use `venv` there)
python -m venv .venv
source .venv/bin/activate

# Install package in editable mode with `dev` requirements to local environment 
pip install -e .[dev]

# Sync project
uv sync --dev
# Activate `venv`
source .venv/bin/activate

If you want to contribute to cythonized extensions you can also install them in editable mode:

pipuv

pip install -e ./py_ballisticcalc.exts[dev]

uv sync --dev --extra exts

Check out a new branch and make your changes¶

Create a new branch for your changes.

# Checkout a new branch and make your changes
git checkout -b my-new-feature-branch
# Make your changes...

Run tests and linting¶

Run tests and linting locally to make sure everything is working as expected.

# Run automated code linting
ruff check

# Run mypy static analysing 
mypy

# Run automated tests
pytest

# Run automated tests for specific engine
pytest --engine="cythonized_rk4_engine"  # via project.entry-points
pytest --engine="my_lib.my_engine:MyEngineClass"  # via entry point path

Coverage¶

We use pytest-cov to get coverage reports:

pytest --cov=py_ballisticcalc --cov-report=html  # for default engine
pytest --cov=py_ballisticcalc --cov-report=html --engine="scipy_engine"  # for custom engine

To get coverage of Cython, set the environment variable CYTHON_COVERAGE = '1', rebuild py_ballisticcalc.exts (from project root: pip install -e py_ballisticcalc.exts), then run:

python scripts/sync_cython_sources.py
pytest --engine="cythonized_rk4_engine" --cov=py_ballisticcalc --cov=py_ballisticcalc_exts --cov-report=html

Cython extensions: safety & stress¶

For diagnosing low-level issues (bounds, None checks, overflows) and for opt-in long-running stress tests, use the safety and stress workflows below. Commands are shown for Windows PowerShell.

# Rebuild Cython extensions with safety checks enabled
$env:CYTHON_SAFETY = '1'
# Optional: force Cython to regenerate C code even if sources look unchanged
$env:CYTHON_FORCE_REGEN = '1'

# Reinstall extensions in editable mode (from project root)
pip install -e ./py_ballisticcalc.exts

# Run extension test suite (stress tests excluded by default via markers)
pytest ./py_ballisticcalc.exts\tests -q

# Run only the stress tests (opt-in). These are longer and more memory-heavy.
pytest ./py_ballisticcalc.exts\tests -m stress -q

# Clear env after testing
Remove-Item Env:CYTHON_SAFETY; Remove-Item Env:CYTHON_FORCE_REGEN

Notes:

Safety build toggles bounds checking, wraparound, initialization checks, None checks, disables cdivision, and adds overflow checks; it trades speed for correctness to surface bugs.
The extension test suite enables faulthandler for better tracebacks on crashes.
Stress tests are marked with @pytest.mark.stress and are excluded by default.

Build Documentation¶

If you have made any changes affecting the documentation (including changes to function signatures, class definitions, or docstrings that will appear in the API documentation), make sure the documentation builds successfully.

We use mkdocs-material[imaging] to support social previews. You can find directions on how to install the required dependencies here.

pipuv

# Install dependencies for docs building
pip install -e .[docs]

# Install dependencies for docs building
uv sync --extra docs

# Rebuild docs locally before commiting them to the branch   
mkdocs build

# Use this command to serve docs locally 
mkdocs serve

If this isn't working due to issues with the imaging plugin, try commenting out the social plugin line in mkdocs.yml and running mkdocs build again.

Commit and push your changes¶

Commit your changes, push your branch to GitHub, and create a pull request.

Please follow the pull request template and fill in as much information as possible. Link to any relevant issues and include a description of your changes.

When your pull request is ready for review, add a comment with the message "please review" and we'll take a look as soon as we can.

Documentation¶

Documentation is written in Markdown and built using Material for MkDocs. API documentation is build from docstrings using mkdocstrings.

In general, documentation should be written in a friendly, approachable style. It should be easy to read and understand, and should be as concise as possible while still being complete.

Code documentation¶

When contributing to py-ballisticcalc, please make sure that all code is well documented. The following should be documented using properly formatted docstrings:

Modules
Class definitions
Function definitions
Module-level variables

py-ballisticcalc uses Google-style docstrings formatted according to PEP 257 guidelines. (See Example Google Style Python Docstrings for further examples.)

pydocstyle is used for linting docstrings. You can run pydocstyle ./py_ballisticcalc\ to check your docstrings.

Where this is a conflict between Google-style docstrings and pydocstyle linting, follow the pydocstyle linting hints.

Class attributes and function arguments should be documented in the format "name: description." When applicable, a return type should be documented with just a description. Types are inferred from the signature/type-hints.

Class attributes should be documented in the class docstring.
Instance attributes should be documented as "Args" in the __init__ docstring.

class Foo:
    """A class docstring.

    Attributes:
        bar: A description of bar. Defaults to "bar".
    """

    bar: str = 'bar'

def bar(self, baz: int) -> str:
    """A function docstring.

    Args:
        baz: A description of `baz`.

    Returns:
        A description of the return value.
    """

    return 'bar'

Code examples are encouraged but should be kept short and simple. However, every code example should be complete, self-contained, and runnable. (If you're not sure how to do this, ask for help!) We prefer print output to naked asserts, but if you're testing something that doesn't have a useful print output, asserts are fine. Code examples should pass doctest, which you can run via scripts\run_doctest.py.

Mermaid¶

We support Mermaid diagrams in Markdown using Material for MkDocs. Use triple backticks with the mermaid fence; no plugin installation is required beyond our existing theme config.

graph LR
    A[Start] --> B{Mermaid enabled?}
    B -- Yes --> C[Write diagrams]
    B -- No --> D[Check mkdocs.yml]

Tips:

Keep fences as ```mermaid (no extra indentation).
Build locally to preview:
```
mkdocs build
mkdocs serve
```
If a diagram renders as plain text, ensure the mermaid fence is exactly specified and not wrapped in another code block.