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 the Ethereum Python Discord server.

Bug Reports

If you think you’ve spotted a bug, open an issue on GitHub with as much detail as possible, preferably with code to reproduce the issue.

Setting the stage

First, you need to clone the repository. depends on submodules, so you need to clone the repo with the --recursive flag. Example:

$ git clone --recursive
$ cd

Install all development dependencies:

$ pip install -e ".[dev]"

Using Docker

Developing within Docker is not required, but if you prefer that workflow, use the sandbox container provided in the docker-compose.yml file.

To start up the test environment, run:

$ docker-compose up -d

This will build a Docker container set up with an environment to run the Python test code.


This container does not have go-ethereum installed, so you cannot run the go-ethereum test suite.

To run the Python tests from your local machine:

$ docker-compose exec sandbox bash -c 'pytest -n 4 -f -k "not goethereum"'

You can run arbitrary commands inside the Docker container by using the bash -c prefix.

$ docker-compose exec sandbox bash -c ''

Or, if you would like to open a session to the container, run:

$ docker-compose exec sandbox bash

Running the tests

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

You can run all tests with:

$ pytest

However, running the entire test suite takes a very long time and is generally impractical. Typically, you’ll just want to run a subset instead, like:

$ pytest tests/core/eth-module/

You can use tox to run all the tests for a given version of Python:

$ tox -e py37-core

Linting is also performed by the CI. You can save yourself some time by checking for linting errors locally:

$ make lint

It is important to understand that each pull request must pass the full test suite as part of the CI check. This test suite will run in the CI anytime a pull request is opened or updated.

Code Style

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

Type Hints

This code base makes use of 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 include type hints, with the exception of tests.

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.

See GitHub’s documentation for working on pull requests.

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. There’s a script to build and install the wheel locally, then generate a temporary virtualenv for smoke testing:

$ git checkout master && git pull

$ make package

# in another shell, navigate to the virtualenv mentioned in output of ^

# load the virtualenv with the packaged release
$ source package-smoke-test/bin/activate

# smoke test the release
$ pip install ipython
$ ipython
>>> from import w3
>>> w3.isConnected()
>>> ...

Verify the latest documentation

To preview the documentation that will get published:

$ make docs

Preview the release notes

$ towncrier --draft

Compile the release notes

After confirming that the release package looks okay, compile the release notes:

$ make notes bump=$$VERSION_PART_TO_BUMP$$

You may need to fix up any broken release note fragments before committing. Keep running make build-docs until it passes, then commit and carry on.

Push the release to GitHub & PyPI

After committing the compiled release notes and pushing them to the master branch, 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 an alpha version, make release bump=stage will bump to beta. If you are in a beta version, make release bump=stage will bump to a stable version.

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".

Generating new fixtures

Our integration tests make use of Geth and Parity/OpenEthereum private networks. When new versions of the client software are introduced, new fixtures should be generated.


A “fixture” is a pre-synced network. It’s the result of configuring and running a client, deploying the test contracts, and saving the resulting state for testing functionality against.

Geth fixtures

  1. Install the desired Geth version on your machine locally. We recommend py-geth for this purpose, because it enables you to easily manage multiple versions of Geth.

    Note that py-geth will need updating to support each new Geth version as well. Add newer Geth version to py-geth is straightforward; see past commits for a template.

    If py-geth has the Geth version you need, install that version locally. For example:

    $ python -m geth.install v1.10.1
  2. Specify the Geth binary and run the fixture creation script (from within the directory):

    $ GETH_BINARY=~/.py-geth/geth-v1.10.1/bin/geth python ./tests/integration/generate_fixtures/ ./tests/integration/geth-1.10.1-fixture
  3. The output of this script is your fixture, a zip file, which is now stored in /tests/integration/. Update the /tests/integration/go_ethereum/ file to point to this new fixture. Delete the old fixture.

  4. Run the tests. To ensure that the tests run with the correct Geth version locally, you may again include the GETH_BINARY environment variable.

Parity/OpenEthereum fixtures

  1. The most reliable way to get a specific Parity/OE binary is to download the source code via GitHub releases.

  2. Build the binary from source. (This is will take a few minutes.)

  3. Specify the path to this binary in the get_parity_binary function of the /tests/integration/generate_fixtures/ file.

  4. Run the fixture generation script:

$ python /tests/integration/generate_fixtures/ /tests/integration/parity-X.Y.Z-fixture
  1. The output of this script is your fixture, a zip file. Store the fixture in the /tests/integration/ directory and update the /tests/integration/parity/ file to point the new fixture.

  2. By this point, you may have noticed that Parity fixture generation relies on a Geth network to sync from. In the output of the generation script are the hashes of the various contracts that it mined. Update the corresponding values in the /parity/ file with those hashes.

  3. Run the tests.