Add workflow to build Python wheels by vepadulano · Pull Request #19456 · root-project/root

vepadulano · 2025-07-24T12:07:25Z

Now that the workflow is fully functional, see e.g. https://github.com/root-project/root/actions/runs/16493485486, I am reopening this PR.

The wheels can be installed on any Linux x86_64 node via:

$: pip install ROOT --index-url=https://root-experimental-python-wheels.web.cern.ch

github-actions · 2025-07-24T12:20:49Z

Test Results

21 files 21 suites 3d 6h 11m 57s ⏱️
3 220 tests 3 220 ✅ 0 💤 0 ❌
65 897 runs 65 897 ✅ 0 💤 0 ❌

Results for commit 7d6cd62.

♻️ This comment has been updated with latest results.

bindings/pyroot/pythonizations/python/ROOT/_rootcli.py

bindings/CMakeLists.txt

cmake/modules/SearchInstalledSoftware.cmake

bindings/pyroot/pythonizations/python/ROOT/__init__.py

bindings/pyroot/pythonizations/python/ROOT/_facade.py

cmake/modules/SearchInstalledSoftware.cmake

setup.py

guitargeek

Thank you so much for this! I'm done with the review.

vepadulano · 2025-07-29T09:55:58Z

Thank you @guitargeek ! I addressed all the review comments, in particular:

I removed the extra subprocess.run call in __init__.py for the moment. It was meant to demonstrate a way to cope with missing dependencies, but probably we need to have a larger discussion about it
I kept for now the tutorials folder as I believe we can use it as a launcher for tests of the wheel, and the extra 25MB at the moment are not a real issue.

guitargeek

Thanks for addressing the comments so quickly, it looks very good now!

Can we just do one CI run with the "clean build" flag please, since you changed "SearchInstalledSoftware.cmake"? And I guess you will also squash the commits a bit 😄

setup.py

After offline discussion, at the moment it looks like having #19470 and #19465 merged would simplify the RPATH logic for the CPython extensions hence improving also the logic for building the Python wheel. We can wait a couple more days before proceeding with this.

vepadulano · 2025-07-30T14:00:30Z

Squashed all changes into a single commit. First commit currently is taken as-is from #19465

setup.py

guitargeek

Thanks a lot for the PR! Works great, also locally for me with pip install root_src/!

setup.py

pyproject.toml

This commit introduces the infrastructure required to build Python wheels from the ROOT project. In turn, these can be used to effectively install the package via `pip install ROOT`. For more details, see https://indico.cern.ch/event/1338689/contributions/6010410/. A Python wheel is a binary archive with the compiled artifacts of a package build. When installing the ROOT package via pip, the package manager will simply decompress the archive and all the ROOT libraries will be ready for use in the user's Python environment. In order to enable building a Python wheel of ROOT, the following changes have been made. First, it is required that all the components of the software do not explicitly link against the Python shared library (e.g. 'libpython.so'). The requirement comes from PEP503 which establishes a portable way to build Python wheels across different platforms, see https://peps.python.org/pep-0513/#libpythonx-y-so-1. Second, the directory structure of the destination user Python environment follows a semi-defined logic, where all artifacts of a package are unpacked at a root directory e.g. `site-packages` inside a sub-directory with the package name, e.g. `site-packages/ROOT`. In order to respect this structure, proper RPATH management of the ROOT libraries and, most notably, the CPython extensions (libROOTPythonizations and cppyy) is required. The `-Drpath=ON` build option is used in the build of the wheel. The CPython extensions are also modified with the right RPATH location. This is handled by building ROOT with the CMake variables CMAKE_INSTALL_BINDIR, CMAKE_INSTALL_INCLUDEDIR, CMAKE_INSTALL_LIBDIR and CMAKE_INSTALL_PYTHONDIR following the `site-packages/ROOT` structure during the build process and then moving the entire directory created this way directly to the target user Python environment directory. On top of being able to use ROOT as a Python package, the project provides a few CLI tools such as `root`. This first commit demonstrates how to also expose these tools in the Python packaging way, i.e. declaring a Python script to the build backend that invokes the correct command. This is defined in the [project.scripts] section of the newly created pyproject.toml file. At the moment, only the `root` command is going to be available from the Python wheel, other commands can be added in the future in a similar way. The wheel of ROOT is currently built via setuptools and using the `manylinux` platform tag to create portable wheels that can work across any Linux x86_64 distribution. One modification particular to the setuptools build is the declaration of a dummy CPython extension module in the setuptools `setup` function. This extensions has no code and takes no part in the build process, but it is enough to signal to the build backend that this package needs to be built for a specific Python version (required at the moment to ensure compatibility of the CPython extensions with the target system). Another issue is pypa/distutils#284, at this moment it looks like more recent versions of setuptools break this CMake extension compatibility. This should be addressed in the future. A new github workflow is written to automatically create Python wheels for every Python version supported by ROOT: 3.8, 3.9, 3.10, 3.11, 3.12 and 3.13 at the time of writing. The workflow is set to run nightly and can be later adjusted to run on specific triggers, e.g. during a PR build with a special label.

guitargeek

Thanks for addressing the comments!

vepadulano requested a review from guitargeek July 24, 2025 12:07

vepadulano self-assigned this Jul 24, 2025

vepadulano requested a review from bellenot as a code owner July 24, 2025 12:07

vepadulano added the in:Python Interface label Jul 24, 2025

vepadulano requested a review from dpiparo as a code owner July 24, 2025 12:07

vepadulano force-pushed the experimental-pip-install-root branch from e376949 to 58efb5c Compare July 25, 2025 10:02

vepadulano mentioned this pull request Jul 25, 2025

pip install ROOT #16669

Closed

vepadulano force-pushed the experimental-pip-install-root branch from 02e1ae6 to aaffbd8 Compare July 29, 2025 08:19