Contributing Guidelines

The source code and issue tracker are hosted on GitHub. Mimesis is tested against Python 3.8 through 3.11 on GitHub Actions and AppVeyor.

Test coverage is monitored with Codecov.

Manage Dependencies

We use poetry to manage dependencies. So, please do not use virtualenv or pip directly. Before going any further, please, take a moment to read the official documentation about poetry to know some basics.

Firstly, install poetry, it is recommended to do so with pip:

~ ⟩ pip install poetry

Installing dependencies

Please, note that poetry will automatically create a virtualenv for this project. It will use you current python version. To install all existing dependencies run:

poetry install

And to activate virtualenv created by poetry run:

poetry shell

Adding new dependencies

To add a new dependency you can run:

  • poetry add --dev pytest to install pytest as a development dependency

Code Style

Every contributor must follow the PEP8 code style. We’re using black for formatting code.


We use optional static typing (mypy). Every function and method should be annotated.

Example of annotated function:

def plus(a: int = 0, b: int = 0) -> int:
    """Get sum of a and b.

    :param a: First number.
    :param b: Second number.
    :return: Sum of a and b.
    return a + b


Always add docstrings for your modules, classes, methods and functions.

Comment only things that are not obvious: hacks, optimizations, complex algorithms. Obvious code does not require any additional comments.


You should write the test which shows that the bug was fixed or that the feature works as expected, run test before you commit your changes to the branch and create PR.

To run tests, simply:

⟩ poetry run pytest

Check out logs of GitHub Actions or AppVeyor if tests were failed on creating PR, there you can find useful information.

The tests are randomly shuffled by pytest-randomly. To rerun the tests with the previous seed use:

) poetry run pytest --randomly-seed=last

If you want to specify a seed ahead of time use:

) poetry run pytest --randomly-seed=$int

Type checking

After adding every feature you should run the type checking and make sure that everything is okay. You can do it using the following command:

⟩ poetry run mypy mimesis/ tests/

Code Review

Contributions will not be merged until they’ve been code reviewed by one of our reviewers. In the event that you object to the code review feedback, you should make your case clearly and calmly. If, after doing so, the feedback is judged to still apply, you must either apply the feedback or withdraw your contribution.


The GitHub issue tracker is for bug reports and feature requests. Please do not create issue which does not related to features or bug reports.

New Locale

We have created a directory with a proper structure that you can use as a great example: mimesis/datasets/locale_template. If you want to add a new locale, this directory can serve as a helpful guide.


We use GitHub Actions for automatically creating releases. The package will be published on PyPi after pushing the new tag to the master branch. The new release can be approved or disapproved by maintainers of this project. If the new release was disapproved, then maintainer should justify why the new release cannot be created.


  • Add one change per one commit.

  • Always comment your code (only in English!).

  • Check your spelling and grammar.

  • Run the tests after each commit.

  • Make sure the tests pass.

  • Make sure that type check is passed.

  • If you add any functionality, then you should add tests for it.

  • Annotate your code.

  • Do not write bad code!