Hi All,

On behalf of the NumPy team, I'm pleased to announce the release of NumPy 1.26.0b1. The NumPy 1.26.0 release is a continuation of the 1.25.x release cycle with the addition of Python 3.12.0 support. Python 3.12 dropped distutils, consequently supporting it required finding a replacement for the setup.py/distutils based build system NumPy was using. We have chosen to use the Meson build system instead, and this is the first NumPy release supporting it. This is also the first release that supports Cython 3.0 in addition to retaining 0.29.X compatibility. Supporting those two upgrades was a large project, over 100 files have been touched in this release. The changelog doesn't capture the full extent of the work, special thanks to Ralf Gommers, Sayed Adel, Stéfan van der Walt, and Matti Picus who did much of the work in the main development branch.

The highlights of this release are:

Python 3.12.0 support.
Cython 3.0.0 compatibility.
Use of the Meson build system
Updated SIMD support

The Python versions supported by this release are 3.9-3.12. Note that no 32 bit wheels are provided. Wheels can be downloaded from PyPI; source archives, release notes, and wheel hashes are available on Github.

Contributors

A total of 11 people contributed to this release. People with a "+" by their names contributed a patch for the first time.

Bas van Beek
Charles Harris
Matti Picus
Melissa Weber Mendonça
Ralf Gommers
Sayed Adel
Sebastian Berg
Stefan van der Walt
Tyler Reddy
Warren Weckesser

Pull requests merged

A total of 18 pull requests were merged for this release.

#24305: MAINT: Prepare 1.26.x branch for development
#24308: MAINT: Massive update of files from main for numpy 1.26
#24322: CI: fix wheel builds on the 1.26.x branch
#24326: BLD: update openblas to newer version
#24327: TYP: Trim down the ``_NestedSequence.__getitem__`` signature
#24328: BUG: fix choose refcount leak
#24337: TST: fix running the test suite in builds without BLAS/LAPACK
#24338: BUG: random: Fix generation of nan by dirichlet.
#24340: MAINT: Dependabot updates from main
#24342: MAINT: Add back NPY_RUN_MYPY_IN_TESTSUITE=1
#24353: MAINT: Update ``extbuild.py`` from main.
#24356: TST: fix distutils tests for deprecations in recent setuptools...
#24375: MAINT: Update cibuildwheel to version 2.15.0
#24381: MAINT: Fix codespaces setup.sh script
#24403: ENH: Vendor meson for multi-target build support
#24404: BLD: vendor meson-python to make the Windows builds with SIMD...
#24405: BLD, SIMD: The meson CPU dispatcher implementation
#24406: MAINT: Remove versioneer

Build system changes

In this release, NumPy has switched to Meson as the build system and
meson-python as the build backend. Installing NumPy or building a wheel can be
done with standard tools like ``pip`` and ``pypa/build``. The following are
supported:

Regular installs: ``pip install numpy`` or (in a cloned repo) ``pip install .``
Building a wheel: ``python -m build`` (preferred), or ``pip wheel .``
Editable installs: ``pip install -e . --no-build-isolation``
Development builds through the custom CLI implemented with spin: ``spin build``.

All the regular ``pip`` and ``pypa/build`` flags (e.g.,
``--no-build-isolation``) should work as expected.

NumPy-specific build customization

Many of the NumPy-specific ways of customizing builds have changed.
The ``NPY_*`` environment variables which control BLAS/LAPACK, SIMD, threading,
and other such options are no longer supported, nor is a ``site.cfg`` file to
select BLAS and LAPACK. Instead, there are command-line flags that can be
passed to the build via ``pip``/``build``'s config-settings interface. These
flags are all listed in the ``meson_options.txt`` file in the root of the repo.
Detailed documented will be available before the final 1.26.0 release; for now
please see `the SciPy building from source docs since most build customization

works in an almost identical way in SciPy as it does in NumPy.

Build dependencies

While the runtime dependencies of NumPy have not changed, the build
dependencies have. Because we temporarily vendor Meson and meson-python,
there are several new dependencies - please see the ``[build-system]`` section
of ``pyproject.toml`` for details.

Troubleshooting

This build system change is quite large. In case of unexpected issues, it is
still possible to use a ``setup.py``-based build as a temporary workaround (on
Python 3.9-3.11, not 3.12), by copying ``pyproject.toml.setuppy`` to
``pyproject.toml``. However, please open an issue with details on the NumPy
issue tracker. We aim to phase out ``setup.py`` builds as soon as possible, and
therefore would like to see all potential blockers surfaced early on in the
1.26.0 release cycle.

Cheers,

Charles Harris