Thank you for your interest in contributing! We welcome all contributions no matter their size. Please read along to learn how to get started. If you get stuck, feel free to reach for help in our Gitter channel.

Setting the stage

First we need to clone the Py-EVM repository. Py-EVM depends on a submodule of the common tests across all clients, so we need to clone the repo with the --recursive flag. Example:

$ git clone --recursive

Optional: Often, the best way to guarantee a clean Python 3 environment is with virtualenv. If we don’t have virtualenv installed already, we first need to install it via pip.

pip install virtualenv

Then, we can initialize a new virtual environment venv, like:

virtualenv -p python3 venv

This creates a new directory venv where packages are installed isolated from any other global packages.

To activate the virtual directory we have to source it

. venv/bin/activate

After we have activated our virtual environment, we need to install all dependencies that are needed to run, develop, and test. This is as easy as navigating to the py-evm directory and running:

pip install -e ".[dev]"

Running the tests

A great way to explore the code base is to run the tests.

We can run all tests with:

pytest tests

However, running the entire test suite does take a very long time so often we just want to run a subset instead, like:

pytest tests/core/padding-utils/

We can also install tox to run the full test suite which also covers things like testing the code against different Python versions, linting etc.

It is important to understand that each Pull Request must pass the full test suite as part of the CI check, hence it is often convenient to have tox installed locally as well.

Code Style

When multiple people are working on the same body of code, it is important that they write code that conforms to a similar style. It often doesn’t matter as much which style, but rather that they conform to one style.

To ensure your contribution conforms to the style being used in this project, we encourage you to read our style guide.

Type Hints

The code bases is transitioning to use type hints. Type hints make it easy to prevent certain types of bugs, enable richer tooling and enhance the documentation, making the code easier to follow.

All new code is required to land with type hints with the exception of test code that is not expected to use type hints.

All parameters as well as the return type of defs are expected to be typed with the exception of self and cls as seen in the following example.

def __init__(self, wrapped_db: DatabaseAPI) -> None:
    self.wrapped_db = wrapped_db


Good documentation will lead to quicker adoption and happier users. Please check out our guide on how to create documentation for the Python Ethereum ecosystem.

Pull Requests

It’s a good idea to make pull requests early on. A pull request represents the start of a discussion, and doesn’t necessarily need to be the final, finished submission.

GitHub’s documentation for working on pull requests is available here.

Once you’ve made a pull request take a look at the Circle CI build status in the GitHub interface and make sure all tests are passing. In general pull requests that do not pass the CI build yet won’t get reviewed unless explicitly requested.

If the pull request introduces changes that should be reflected in the release notes, please add a newsfragment file as explained here.

If possible, the change to the release notes file should be included in the commit that introduces the feature or bugfix.


Final test before each release

Before releasing a new version, build and test the package that will be released:

git checkout master && git pull

make package

# Preview the upcoming release notes
towncrier --draft

Build the release notes

Before bumping the version number, build the release notes. You must include the part of the version to bump (see below), which changes how the version number will show in the release notes.

make notes bump=$$VERSION_PART_TO_BUMP$$

If there are any errors, be sure to re-run make notes until it works.

Push the release to github & pypi

After confirming that the release package looks okay, release a new version:

make release bump=$$VERSION_PART_TO_BUMP$$

Which version part to bump

The version format for this repo is {major}.{minor}.{patch} for stable, and {major}.{minor}.{patch}-{stage}.{devnum} for unstable (stage can be alpha or beta).

During a release, specify which part to bump, like make release bump=minor or make release bump=devnum.

If you are in a beta version, make release bump=stage will switch to a stable.

To issue an unstable version when the current version is stable, specify the new version explicitly, like make release bump="--new-version 4.0.0-alpha.1 devnum"