Developer guide

PyRanges is mainly developed by Endre Bakken Stovner and by the Comparative Genomics lab of Marco Mariotti. It follows the guidelines for open source software, and external contributors are welcome. The code is centralized on github, at

Bugs and feature requests can be reported as github issues. You may also contribute by submitting your own code edits, either to deal with issues or to add new functionalities. The code will be reviewed by the core development team, which may integrate it in the main repository. Contributions are tracked by github and are publicly visible.

Below, we sketch a guide to contribute to PyRanges. It assumes familiarity with python and with the terminal, and minimal experience with git/github. Before the actual list of steps follow (Task sequence), we go over some essential concepts used in the “continuous integration” system in place to maintain and evolve pyranges.


Tests are an essential part of continuous integration. Briefly, they ensure that code edits do not break existing functions. Various layers of tests are implemented in pyranges:

  • unit tests: quick and compulsory tests about the main pyranges functionalities

  • doctest: quick and compulsory tests that ensures that the code in the documentation (tutorial and how-to-pages) gives the expected results

  • property based tests: time-consuming tests that involve the generation of random data to check that the results of pyranges functions match that of other reference bioinformatic tools. These tests are not compulsory: the core development team runs them when the code backbone is edited.

If the code submitted to pyranges does not pass the compulsory tests, it will not be integrated. Therefore, we highly recommend developers to run tests before code submissions, as explained further below.

Documentation: docstrings

Python docstrings are widely used to document the rationale, input arguments, and returned values of all functions and methods. The use of a consistent docstring style allows the automatic generation of API documentation, as seen in pyranges documentation at, built through the Sphynx software.

Pyranges adopts the NumPy/SciPy-style: It is important that code contributors who edit any function also update their docstrings to reflect how it works; and that all new functions contain an appropriate docstring. Follow the link above and inspect existing pyranges code to write good docstrings.

Code formatting and linting

Pyranges code follows strict guidelines about its formatting and non-redundancy. This burden is not upon the developer: instead, this is achieved by running dedicated software that polishes, formats, and “lints” the code before its integration in the main repository. These tools are used:

  • black: code formatter

  • flake8: code linting

  • isort: sort import statements

  • mypy: type checking (optional, for functions with a defined return type)

Task sequence

1. Set up your developer environment

We recommend creating an environment dedicated to the development of pyranges:

conda create -n prdev python pip
conda activate prdev

Next, install additional packages required for testing and linting code, and for checking the automated documentation:

pip install flake8 black isort hypothesis pytest \
 pytest-watch sphinx sphinx-autoapi sphinxcontrib-napoleon \
 pyfaidx pyBigWig sphinx_rtd_theme

2. Create and setup your own PyRanges fork

The easiest way to do this is through github. Login into the github website if you aren’t already, then visit, and click “Fork” on the top right. Fill the form and confirm. In the page of your new fork, find the <> Code button, and copy the https address. On your computer, create a new folder dedicated to the project, then clone your fork inside it:

mkdir pr_debug
cd pr_debug

Next, cd into your pyranges fork, and install it locally with pip as shown below. By using pip option -e, your installation is in “editable” mode: any changes you make to your pyranges code will be immediately reflected in your environment. In other words, you won’t need to re-run pip install every time you change something in the code.

cd pyranges
pip install -e .

3. Edit the code

Now, you’re ready to edit the code in the pyranges/ folder.

To run your code to see that it behaves as intended, we recommend using a separate script that imports pyranges, making sure you’re in the prdev conda environment.

4. Format and lint code

Run these commands from inside your pyranges folder (which has a pyranges subfolder):

black -l 120 pyranges/
isort --profile black -l 120 tests pyranges
flake8  --max-line-length=120 --ignore E203,E501,W503 tests pyranges

5. Inspect the Sphynx documentation

Your code edits may warrant edits in the pyranges docstrings. In this case, it is compelling to locally check that the automatically generated documentation is built appropriately. Inside the pyranges folder, run these commands:

cd docs
make html
cd -

If the “make” command has no major errors, it will generate the full pyranges documentation in the form of html pages, identical to Open the file docs/build/html/index.html with a browser to inspect all the parts that may have been affected by your changes, and fix any potential problems. To know more about its inner workings, read about the Sphynx system.

6. Run tests

For each of the tests, inspect the output of py.test: warnings are acceptable, but errors must be fixed. To run the unit tests, run this from inside your pyranges folder:

py.test tests/unit

To run the doctest, run this:

py.test tests/tutorial_doctest

To run the non-compulsory property-based tests, run:

py.test tests/property_based/

If all tests have worked correctly, you are ready to submit your code for integration into the main pyranges repository; that is to say, to open a “pull request”. Before you can do that, you have to update your remote repository, i.e. your pyranges fork at github.

7. Log your changes

First, bump the version number in the file pyproject.toml. Then, it’s essential to document your changes in the CHANGE_LOG.txt file. This log should provide a clear and concise summary of the modifications, additions, and fixes made in each version of your project. Include relevant details such as feature enhancements, bug fixes, and any other notable alterations to help maintain a transparent and informative record of your project’s evolution.

8. Push to your remote repository

Run this command to list all the local files you modified:

git status

You must tell git which of these files have to be synchronized, i.e. “git add” them. You can do this by explicitly providing the list of files with:

git add file1 file2 ... fileN

Alternatively to the previous command, if you want to add ALL edited files, you can use:

git add . --dry-run

to check the list of all modified files, then this to actually add them:

git add .

After adding files, you have commit your changes locally with:

git commit -m"Include an informative message here"

Finally, push to your remote repository, i.e. update your online fork at github, with:

git push

You will be requested your github credentials. Note that your online password may not work; in this case, google how to set up a github token that you can use.

9. Open a pull request

The easiest way to open a pull request is through the github website. Go to your pyranges fork on github, then find the “Contribute” button (near the <> Code button). Click it, and select Open pull request.

In the newly opened page, carefully check that source and destination are correctly selected. The Base repository should be pyranges/pyranges (i.e. the main pyranges repo), and the Head repository should be your fork. If you worked on non-master git branches, select them here.

In the comments, write a summary of the introduced changes and their rationale, tagging any related github issues (i.e. paste their http address). On the rest of the page, you are presented with a list of the code edits. When you’re ready, click “Open pull request”.

10. Core team only: upload to PyPI

Every now and then, the core development team considers that a new pyranges version should be released. To do so:

  • Update the version number in the pyproject.toml file

  • Find the “Build and upload to PyPI” workflow in the left menu of the github actions at

  • Click the “Run workflow” button on the right

Next, check that everything worked correctly, by confirming that a new pyranges installation via pip selects the new version.

Finally, the pyranges conda package at Bioconda is updated automatically upon pip upload. Check that this is updated correctly.