Contributing#

We absolutely welcome contributions and we hope that this guide will facilitate an understanding of the PyVista code repository. It is important to note that the PyVista software package is maintained on a volunteer basis and thus we need to foster a community that can support user questions and develop new features to make this software a useful tool for all users.

This page is dedicated to outline where you should start with your question, concern, feature request, or desire to contribute.

Being Respectful#

Please demonstrate empathy and kindness toward other people, other software, and the communities who have worked diligently to build (un-)related tools.

Please do not talk down in Pull Requests, Issues, or otherwise in a way that portrays other people or their works in a negative light.

Cloning the Source Repository#

You can clone the source repository from pyvista/pyvista and install the latest version by running:

git clone https://github.com/pyvista/pyvista.git
cd pyvista
python -m pip install -e .

Questions#

For general questions about the project, its applications, or about software usage, please create a discussion in the Discussions repository where the community can collectively address your questions. You are also welcome to join us on Slack or send one of the developers an email. The project support team can be reached at info@pyvista.org

For more technical questions, you are welcome to create an issue on the issues page which we will address promptly. Through posting on the issues page, your question can be addressed by community members with the needed expertise and the information gained will remain available on the issues page for other users.

Reporting Bugs#

If you stumble across any bugs, crashes, or concerning quirks while using code distributed here, please report it on the issues page with an appropriate label so we can promptly address it. When reporting an issue, please be overly descriptive so that we may reproduce it. Whenever possible, please provide tracebacks, screenshots, and sample files to help us address the issue.

Feature Requests#

We encourage users to submit ideas for improvements to PyVista code base! Please create an issue on the issues page with a Feature Request label to suggest an improvement. Please use a descriptive title and provide ample background information to help the community implement that functionality. For example, if you would like a reader for a specific file format, please provide a link to documentation of that file format and possibly provide some sample files with screenshots to work with. We will use the issue thread as a place to discuss and provide feedback.

Contributing New Code#

If you have an idea for how to improve PyVista, please first create an issue as a feature request which we can use as a discussion thread to work through how to implement the contribution.

Once you are ready to start coding and develop for PyVista, please see the Development Practices section for more details.

Licensing#

All contributed code will be licensed under The MIT License found in the repository. If you did not write the code yourself, it is your responsibility to ensure that the existing license is compatible and included in the contributed files or you can obtain permission from the original author to relicense the code.


Development Practices#

This section provides a guide to how we conduct development in the PyVista repository. Please follow the practices outlined here when contributing directly to this repository.

Guidelines#

Through direct access to the Visualization Toolkit (VTK) via direct array access and intuitive Python properties, we hope to make the entire VTK library easily accessible to researchers of all disciplines. To further PyVista towards being the de facto Python interface to VTK, we need your help to make it even better!

If you want to add one or two interesting analysis algorithms as filters, implement a new plotting routine, or just fix 1-2 typos - your efforts are welcome!

There are three general coding paradigms that we believe in:

  1. Make it intuitive. PyVista’s goal is to create an intuitive and easy to use interface back to the VTK library. Any new features should have intuitive naming conventions and explicit keyword arguments for users to make the bulk of the library accessible to novice users.

  2. Document everything! At the least, include a docstring for any method or class added. Do not describe what you are doing but why you are doing it and provide a simple example for the new features.

  3. Keep it tested. We aim for a high test coverage. See testing for more details.

There are two important copyright guidelines:

  1. Please do not include any data sets for which a license is not available or commercial use is prohibited. Those can undermine the license of the whole projects.

  2. Do not use code snippets for which a license is not available (e.g. from stackoverflow) or commercial use is prohibited. Those can undermine the license of the whole projects.

Please also take a look at our Code of Conduct.

Contributing to PyVista through GitHub#

To submit new code to pyvista, first fork the pyvista GitHub Repo and then clone the forked repository to your computer. Then, create a new branch based on the Branch Naming Conventions Section in your local repository.

Next, add your new feature and commit it locally. Be sure to commit frequently as it is often helpful to revert to past commits, especially if your change is complex. Also, be sure to test often. See the Testing Section below for automating testing.

When you are ready to submit your code, create a pull request by following the steps in the Creating a New Pull Request section.

Coding Style#

We adhere to PEP 8 wherever possible, except that line widths are permitted to go beyond 79 characters to a max of 99 characters for code. This should tend to be the exception rather than the norm. A uniform code style is enforced by black to prevent energy wasted on style disagreements.

As for docstrings, follow the guidelines specified in PEP 8 Maximum Line Length of limiting docstrings to 72 characters per line. This follows the directive:

Some teams strongly prefer a longer line length. For code maintained exclusively or primarily by a team that can reach agreement on this issue, it is okay to increase the line length limit up to 99 characters, provided that comments and docstrings are still wrapped at 72 characters.

Outside of PEP 8, when coding please consider PEP 20 – The Zen of Python. When in doubt:

import this

PyVista uses pre-commit to enforce PEP8 and other styles automatically. Please see the Style Checking section for further details.

Docstrings#

PyVista uses Python docstrings to create reference documentation for our Python APIs. Docstrings are read by developers, interactive Python users, and readers of our online documentation. This section describes how to write these docstrings for PyVista.

PyVista follows the numpydoc style for its docstrings. Please follow the numpydoc Style Guide in all ways except for the following:

  • Be sure to describe all Parameters and Returns for all public methods.

  • We strongly encourage you to add an example section. PyVista is a visual library, so adding examples that show a plot will really help users figure out what individual methods do.

  • With optional parameters, use default: <value> instead of optional when the parameter has a default value instead of None.

Sample docstring follows:

def slice_x(self, x=None, generate_triangles=False):
    """Create an orthogonal slice through the dataset in the X direction.

    Parameters
    ----------
    x : float, optional
        The X location of the YZ slice. By default this will be the X center
        of the dataset.

    generate_triangles : bool, default: False
        If this is enabled, the output will be all triangles. Otherwise the
        output will consist of the intersection polygons.

    Returns
    -------
    pyvista.PolyData
        Sliced dataset.

    Examples
    --------
    Slice the random hills dataset with one orthogonal plane.

    >>> from pyvista import examples
    >>> hills = examples.load_random_hills()
    >>> slices = hills.slice_x(5, generate_triangles=False)
    >>> slices.plot(line_width=5)

    See :ref:`slice_example` for more examples using this filter.

    """

    pass  # implementation goes here

Note the following:

  • The parameter definition of generate_triangles uses default: False, and does not include the default in the docstring’s “description” section.

  • There is a newline between each parameter. This is different than numpydoc’s documentation where there are no empty lines between parameter docstrings.

  • This docstring also contains a returns section and an examples section.

  • The returns section does not include the parameter name if the function has a single return value. Multiple return values (not shown) should have descriptive parameter names for each returned value, in the same format as the input parameters.

  • The examples section references the “full example” in the gallery if it exists.

Deprecating Features or other Backwards-Breaking Changes#

When implementing backwards-breaking changes within PyVista, care must be taken to give users the chance to adjust to any new changes. Any non-backwards compatible modifications should proceed through the following steps:

  1. Retain the old behavior and issue a PyVistaDeprecationWarning indicating the new interface you should use.

  2. Retain the old behavior but raise a pyvista.core.errors.DeprecationError indicating the new interface you must use.

  3. Remove the old behavior.

Whenever possible, PyVista developers should seek to have at least three minor versions of backwards compatibility to give users the ability to update their software and scripts.

Here’s an example of a soft deprecation of a function. Note the usage of both the PyVistaDeprecationWarning warning and the .. deprecated Sphinx directive.

def addition(a, b):
    """Add two numbers.

    .. deprecated:: 0.37.0
       Since PyVista 0.37.0, you can use :func:`pyvista.add` instead.

    Parameters
    ----------
    a : float
        First term to add.

    b : float
        Second term to add.

    Returns
    -------
    float
        Sum of the two inputs.

    """
    # deprecated 0.37.0, convert to error in 0.40.0, remove 0.41.0
    PyVistaDeprecationWarning(
        '`addition` has been deprecated. Use pyvista.add instead'
    )
    add(a, b)


def add(a, b):
    """Add two numbers."""

    pass  # implementation goes here

In the above code example, note how a comment is made to convert to an error in three minor releases and completely remove in the following minor release. For significant changes, this can be made longer, and for trivial ones this can be kept short.

When adding an additional parameter to an existing method or function, you are encouraged to use the .. versionadded sphinx directive. For example:

def Cube(clean=True):
    """Create a cube.

    Parameters
    ----------
    clean : bool, default: True
        Whether to clean the raw points of the mesh.

        .. versionadded:: 0.33.0
    """

Branch Naming Conventions#

To streamline development, we have the following requirements for naming branches. These requirements help the core developers know what kind of changes any given branch is introducing before looking at the code.

  • fix/: any bug fixes, patches, or experimental changes that are minor

  • feat/: any changes that introduce a new feature or significant addition

  • junk/: for any experimental changes that can be deleted if gone stale

  • maint/: for general maintenance of the repository or CI routines

  • doc/: for any changes only pertaining to documentation

  • no-ci/: for low impact activity that should NOT trigger the CI routines

  • testing/: improvements or changes to testing

  • release/: releases (see below)

  • breaking-change/: Changes that break backward compatibility

Testing#

After making changes, please test changes locally before creating a pull request. The following tests will be executed after any commit or pull request, so we ask that you perform the following sequence locally to track down any new issues from your changes.

To run our comprehensive suite of unit tests, install all the dependencies listed in requirements_test.txt and requirements_docs.txt:

pip install -r requirements_test.txt
pip install -r requirements_docs.txt

Then, if you have everything installed, you can run the various test suites.

Using Gitpod workspace#

A prebuilt gitpod workspace is available for a quick start development environment. To start a workspace from the main branch of pyvista, go to https://gitpod.io/#https://github.com/pyvista/pyvista. See Gitpod Getting Started for more details.

The workspace has vnc capability through the browser for interactive plotting. The workspace also has prebuilt documentation with a live-viewer. Hit the Go Live button and browse to doc/_build/html. The workspace is also prebuilt to support pre-commit checks.

Workspaces started from the pyvista/pyvista repo will often have prebuilt environments with dependencies installed. Workspaces started from forks may not have prebuilt images and will start building when starting a new workspace. It is safe to stop, e.g. Ctrl-C, the documentation part of the build if unneeded.

Unit Testing#

Run the primary test suite and generate coverage report:

python -m pytest -v --cov pyvista

Unit testing can take some time, if you wish to speed it up, set the number of processors with the -n flag. This uses pytest-xdist to leverage multiple processes. Example usage:

python -m pytest -n <NUMCORE> --cov pyvista

Documentation Testing#

Run all code examples in the docstrings with:

python -m pytest -v --doctest-modules pyvista

Style Checking#

PyVista follows PEP8 standard as outlined in the Coding Style section and implements style checking using pre-commit.

To ensure your code meets minimum code styling standards, run:

pip install pre-commit
pre-commit run --all-files

If you have issues related to setuptools when installing pre-commit, see pre-commit Issue #2178 comment for a potential resolution.

You can also install this as a pre-commit hook by running:

pre-commit install

This way, it’s not possible for you to push code that fails the style checks. For example, each commit automatically checks that you meet the style requirements:

$ pre-commit install
$ git commit -m "added my cool feature"
black....................................................................Passed
isort....................................................................Passed
flake8...................................................................Passed
codespell................................................................Passed

The actual installation of the environment happens before the first commit following pre-commit install. This will take a bit longer, but subsequent commits will only trigger the actual style checks.

Notes Regarding Image Regression Testing#

Since PyVista is primarily a plotting module, it’s imperative we actually check the images that we generate in some sort of regression testing. In practice, this ends up being quite a bit of work because:

  • OpenGL software vs. hardware rending causes slightly different images to be rendered.

  • We want our CI (which uses a virtual frame buffer) to match our desktop images (uses hardware acceleration).

  • Different OSes render different images.

As each platform and environment renders different slightly images relative to Linux (which these images were built from), so running these tests across all OSes isn’t optimal. We could generate different images for each OS, but it’s overkill in my opinion; we need to know if something fundamental changed with our plotting without actually looking at the plots (like the docs at dev.pyvista.com)

Based on these points, image regression testing only occurs on Linux CI, and multi-sampling is disabled as that seems to be one of the biggest difference between software and hardware based rendering.

Image cache is stored here as ./tests/plotting/image_cache.

Image resolution is kept low at 400x400 as we don’t want to pollute git with large images. Small variations between versions and environments are to be expected, so error < IMAGE_REGRESSION_ERROR is allowable (and will be logged as a warning) while values over that amount will trigger an error.

There are two mechanisms within pytest to control image regression testing, --reset_image_cache and --ignore_image_cache. For example:

pytest tests/plotting --reset_image_cache

Running --reset_image_cache creates a new image for each test in tests/plotting/test_plotting.py and is not recommended except for testing or for potentially a major or minor release. You can use --ignore_image_cache if you’re running on Linux and want to temporarily ignore regression testing. Realize that regression testing will still occur on our CI testing.

Images are currently only cached from tests in tests/plotting/test_plotting.py. By default, any test that uses Plotter.show will cache images automatically. To skip image caching, the verify_image_cache fixture can be utilized:

@skip_no_plotting
def test_add_background_image_not_global(verify_image_cache):
    verify_image_cache.skip = True  # Turn off caching
    plotter = pyvista.Plotter()
    plotter.add_mesh(sphere)
    plotter.show()
    # Turn on caching for further plotting
    verify_image_cache.skip = False
    ...

This ensures that immediately before the plotter is closed, the current render window will be verified against the image in CI. If no image exists, be sure to add the resulting image with

git add tests/plotting/image_cache/*

During unit testing, if you get image regression failures and would like to compare the images generated locally to the regression test suite, allow pytest-pyvista to write all new generated images to a local directory using the --generated_image_dir flag.

For example, the following writes all images generated by pytest to debug_images/ for any tests in tests/plotting whose function name has volume in it.

pytest tests/plotting/ -k volume --generated_image_dir debug_images

Building the Documentation#

Build the documentation on Linux or Mac OS with:

make -C doc html

Build the documentation on Windows with:

cd doc python -msphinx -M html . _build

The generated documentation can be found in the doc/_build/html directory.

The first time you build the documentation locally will take a while as all the examples need to be built. After the first build, the documentation should take a fraction of the time.

Clearing the local build#

If you need to clear the locally built documentation, run:

make -C doc clean

This will clear out everything, including the examples gallery. If you only want to clear everything except the gallery examples, run:

make -C doc clean-except-examples

This will clear out the cache without forcing you to rebuild all the examples.

Parallel Documentation Build#

You can improve your documentation build time on Linux and Mac OS with:

make -C doc phtml

This effectively invokes SPHINXOPTS=-j and can be especially useful for multi-core computers when FULL_DOC_BUILD=TRUE

Contributing to the Documentation#

Documentation for PyVista is generated from three sources:

  • Docstrings from the classes, functions, and modules of pyvista using sphinx.ext.autodoc.

  • Restructured test from doc/

  • Gallery examples from examples/

General usage and API descriptions should be placed within doc/api and the docstrings. Full gallery examples should be placed in examples.

Adding a New Example#

PyVista’s examples come in two formats: basic code snippets demonstrating the functionality of an individual method or a full gallery example displaying one or more concepts. Small code samples and snippets are contained in the doc/api directory or within our documentation strings, while the full gallery examples, meant to be run as individual downloadable scripts, are contained in the examples directory at the root of this repository.

To add a fully fledged, standalone example, add your example to the examples directory in the root directory of the PyVista Repository within one of the applicable subdirectories. Should none of the existing directories match the category of your example, create a new directory with a README.txt describing the new category. Additionally, as these examples are built using the sphinx gallery extension, follow coding guidelines as established by Sphinx-Gallery.

For more details see Adding a New Gallery Example.

Add a new Example File#

If you have a dataset that you need for your gallery example, add it to pyvista/vtk-data and follow the directions there. You will then need to add a new function to download the dataset pyvista/examples/downloads.py. This might be as easy as:

def download_my_dataset(load=True):
    """Download my new dataset."""
    return _download_and_read('mydata/my_new_dataset.vtk', load=load)

Which enables:

>>> from pyvista import examples
>>> dataset = examples.download_my_dataset()

Creating a New Pull Request#

Once you have tested your branch locally, create a pull request on pyvista GitHub while merging to main. This will automatically run continuous integration (CI) testing and verify your changes will work across several platforms.

To ensure someone else reviews your code, at least one other member of the pyvista contributors group must review and verify your code meets our community’s standards. Once approved, if you have write permission you may merge the branch. If you don’t have write permission, the reviewer or someone else with write permission will merge the branch and delete the PR branch.

Since it may be necessary to merge your branch with the current release branch (see below), please do not delete your branch if it is a fix/ branch.

Branching Model#

This project has a branching model that enables rapid development of features without sacrificing stability, and closely follows the Trunk Based Development approach.

The main features of our branching model are:

  • The main branch is the main development branch. All features, patches, and other branches should be merged here. While all PRs should pass all applicable CI checks, this branch may be functionally unstable as changes might have introduced unintended side-effects or bugs that were not caught through unit testing.

  • There will be one or many release/ branches based on minor releases (for example release/0.24) which contain a stable version of the code base that is also reflected on PyPI/. Hotfixes from fix/ branches should be merged both to main and to these branches. When necessary to create a new patch release these release branches will have their pyvista/_version.py updated and be tagged with a semantic version (e.g. v0.24.1). This triggers CI to push to PyPI, and allow us to rapidly push hotfixes for past versions of pyvista without having to worry about untested features.

  • When a minor release candidate is ready, a new release branch will be created from main with the next incremented minor version (e.g. release/0.25), which will be thoroughly tested. When deemed stable, the release branch will be tagged with the version (v0.25.0 in this case), and if necessary merged with main if any changes were pushed to it. Feature development then continues on main and any hotfixes will now be merged with this release. Older release branches should not be deleted so they can be patched as needed.

Minor Release Steps#

Minor releases are feature and bug releases that improve the functionality and stability of pyvista. Before a minor release is created the following will occur:

  1. Create a new branch from the main branch with name release/MAJOR.MINOR (e.g. release/0.25).

  2. Locally run all tests as outlined in the Testing Section and ensure all are passing.

  3. Locally test and build the documentation with link checking to make sure no links are outdated. Be sure to run make clean to ensure no results are cached.

    cd doc
    make clean  # deletes the sphinx-gallery cache
    make doctest-modules
    make html -b linkcheck
    
  4. After building the documentation, open the local build and examine the examples gallery for any obvious issues.

  5. Update the development version numbers in pyvista/_version.py and commit it (e.g. 0, 26, 'dev0'). Push the branch to GitHub and create a new PR for this release that merges it to main. Development to main should be limited at this point while effort is focused on the release.

  6. It is now the responsibility of the pyvista community to functionally test the new release. It is best to locally install this branch and use it in production. Any bugs identified should have their hotfixes pushed to this release branch.

  7. When the branch is deemed as stable for public release, the PR will be merged to main. After update the version number in release/MAJOR.MINOR branch, the release/MAJOR.MINOR branch will be tagged with a vMAJOR.MINOR.0 release. The release branch will not be deleted. Tag the release with:

    git tag v$(python -c "import pyvista as pv; print(pv.__version__)")
    git push origin --tags
    
  8. Create a list of all changes for the release. It is often helpful to leverage GitHub’s compare feature to see the differences from the last tag and the main branch. Be sure to acknowledge new contributors by their GitHub username and place mentions where appropriate if a specific contributor is to thank for a new feature.

  9. Place your release notes from step 8 in the description for the new release on GitHub.

  10. Go grab a beer/coffee/water and wait for @regro-cf-autotick-bot to open a pull request on the conda-forge PyVista feedstock. Merge that pull request.

  11. Announce the new release in the PyVista Slack workspace and celebrate!

Patch Release Steps#

Patch releases are for critical and important bugfixes that can not or should not wait until a minor release. The steps for a patch release

  1. Push the necessary bugfix(es) to the applicable release branch. This will generally be the latest release branch (e.g. release/0.25).

  2. Update pyvista/_version.py with the next patch increment (e.g. v0.25.1), commit it, and open a PR that merge with the release branch. This gives the pyvista community a chance to validate and approve the bugfix release. Any additional hotfixes should be outside of this PR.

  3. When approved, merge with the release branch, but not main as there is no reason to increment the version of the main branch. Then create a tag from the release branch with the applicable version number (see above for the correct steps).

  4. If deemed necessary, create a release notes page. Also, open the PR from conda and follow the directions in step 10 in the minor release section.