Setting up a development environment#

The HoloViews library is a project that provides a wide range of data interfaces and an extensible set of plotting backends, which means the development and testing process involves a broad set of libraries.

This guide describes how to install and configure development environments.

If you have any problems with the steps here, please reach out in the dev channel on Discord or on Discourse.


Basic understanding of how to contribute to Open Source#

If this is your first open-source contribution, please study one or more of the below resources.


The HoloViews source code is stored in a Git source control repository. The first step to working on HoloViews is to install Git onto your system. There are different ways to do this, depending on whether you use Windows, Mac, or Linux.

To install Git on any platform, refer to the Installing Git section of the Pro Git Book.

To contribute to HoloViews, you will also need Github account and knowledge of the fork and pull request workflow.


Developing all aspects of HoloViews requires a wide range of packages in different environments. To make this more manageable, Pixi manages the developer experience. To install Pixi, follow this guide.


  • Tasks: A task is what can be run with pixi run <task-name>. Tasks can be anything from installing packages to running tests.

  • Environments: An environment is a set of packages installed in a virtual environment. Each environment has a name; you can run tasks in a specific environment with the -e flag. For example, pixi run -e test-core test-unit will run the test-unit task in the test-core environment.

  • Lock-file: A lock-file is a file that contains all the information about the environments.

For more information, see the Pixi documentation.


The first time you run pixi, it will create a .pixi directory in the source directory. This directory will contain all the files needed for the virtual environments. The .pixi directory can be large, so it is advised not to put the source directory into a cloud-synced directory.

Installing the Project#

Cloning the Project#

The source code for the HoloViews project is hosted on GitHub. The first thing you need to do is clone the repository.

  1. Go to

  2. Fork the repository

  3. Run in your terminal: git clone<Your Username Here>/holoviews

The instructions for cloning above created a holoviews directory at your file system location. This holoviews directory is the source checkout for the remainder of this document, and your current working directory is this directory.

Start developing#

To start developing, run the following command

pixi install

The first time you run it, it will create a pixi.lock file with information for all available environments. This command will take a minute or so to run. When this is finished, it is possible to run the following command to download the data HoloViews tests and examples depend upon.

pixi run download-data

All available tasks can be found by running pixi task list, the following sections will give a brief introduction to the most common tasks.

Syncing Git tags with upstream repository#

If you are working from a forked repository of HoloViews, you will need to sync the tags with the upstream repo. This is needed because the HoloViews version number depends on git tags. Syncing the git tags can be done with:

pixi run sync-git-tags

Editable install#

It can be advantageous to install the HoloViews in editable mode:

pixi run install


Currently, this needs to be run for each environment. So, if you want to install in the test-ui environment, you can add --environment / -e to the command:

pixi run -e test-ui install


HoloViews uses pre-commit to apply linting to HoloViews code. Linting can be run for all the files with:

pixi run lint

Linting can also be set up to run automatically with each commit; this is the recommended way because if linting is not passing, the Continuous Integration (CI) will also fail.

pixi run lint-install


To help keep HoloViews maintainable, all Pull Requests (PR) with code changes should typically be accompanied by relevant tests. While exceptions may be made for specific circumstances, the default assumption should be that a Pull Request without tests will not be merged.

There are three types of tasks and five environments related to tests.

Unit tests#

Unit tests are usually small tests executed with pytest. They can be found in holoviews/tests/. Unit tests can be run with the test-unit task:

pixi run test-unit

The task is available in the following environments: test-39, test-310, test-311, test-312, and test-core. Where the first ones have the same environments except for different Python versions, and test-core only has a core set of dependencies.

If you haven’t set the environment flag in the command, a menu will help you select which one of the environments to use.

Example tests#

HoloViews’s documentation consists mainly of Jupyter Notebooks. The example tests execute all the notebooks and fail if an error is raised. Example tests are possible thanks to nbval and can be found in the examples/ folder. Example tests can be run with the following command:

pixi run test-example

This task has the same environments as the unit tests except for test-core.

UI tests#

HoloViews provides web components that users can interact with through the browser. UI tests allow checking that these components get displayed as expected and that the backend <-> front-end bi-communication works correctly. UI tests are possible thanks to Playwright. The test can be found in the holoviews/tests/ui/ folder. UI tests can be run with the following task. This task is only available in the test-ui environment. The first time you run it, it will download the necessary browser files to run the tests in the Chrome browser.

pixi run test-ui


The documentation can be built with the command:

pixi run docs-build

As HoloViews uses notebooks for much of the documentation, this will take significant time to run (around an hour). If you want to run it locally, you can temporarily disable the gallery by setting the environment variable export HV_DOC_GALLERY=False. You can also disable the reference gallery by setting the environment variable export HV_DOC_REF_GALLERY=False.

A development version of HoloViews can be found here. You can ask a maintainer if they want to make a dev release for your PR, but there is no guarantee they will say yes.


HoloViews have two build tasks. One is for building packages for Pip, and the other is for building packages for Conda.

pixi run build-pip
pixi run build-conda

Continuous Integration#

Every push to the main branch or any PR branch on GitHub automatically triggers a test build with GitHub Actions.

You can see the list of all current and previous builds at this URL


GitHub Actions provides free build workers for open-source projects. A few considerations will help you be considerate of others needing these limited resources:

  • Run the tests locally before opening or pushing to an opened PR.

  • Group commits to meaningful chunks of work before pushing to GitHub (i.e., don’t push on every commit).