# Status of `numpy.distutils` and migration advice

`numpy.distutils` has been deprecated in NumPy `1.23.0`. It will be removed for Python 3.12; for Python <= 3.11 it will not be removed until 2 years after the Python 3.12 release (Oct 2025).

Warning

`numpy.distutils` is only tested with `setuptools < 60.0`, newer versions may break. See Interaction of numpy.disutils with setuptools for details.

## Migration advice

It is not necessary to migrate immediately - the release date for Python 3.12 is October 2023. It may be beneficial to wait with migrating until there are examples from other projects to follow (see below).

There are several build systems which are good options to migrate to. Assuming you have compiled code in your package (if not, we recommend using Flit) and you want to be using a well-designed, modern and reliable build system, we recommend:

1. Meson

2. CMake (or scikit-build as an interface to CMake)

If you have modest needs (only simple Cython/C extensions, and perhaps nested `setup.py` files) and have been happy with `numpy.distutils` so far, you can also consider switching to `setuptools`. Note that most functionality of `numpy.disutils` is unlikely to be ported to `setuptools`.

### Moving to Meson

SciPy is moving to Meson for its 1.9.0 release, planned for July 2022. During this process, any remaining issues with Meson’s Python support and achieving feature parity with `numpy.distutils` will be resolved. Note: parity means a large superset, but right now some BLAS/LAPACK support is missing and there are a few open issues related to Cython. SciPy uses almost all functionality that `numpy.distutils` offers, so if SciPy has successfully made a release with Meson as the build system, there should be no blockers left to migrate, and SciPy will be a good reference for other packages who are migrating. For more details about the SciPy migration, see:

- RFC: switch to Meson as a build system

- Tracking issue for Meson support

NumPy itself will very likely migrate to Meson as well, once the SciPy migration is done.

### Moving to CMake / scikit-build

See the scikit-build documentation for how to use scikit-build. Please note that as of Feb 2022, scikit-build still relies on setuptools, so it’s probably not quite ready yet for a post-distutils world. How quickly this changes depends on funding, the current (Feb 2022) estimate is that if funding arrives then a viable `numpy.distutils` replacement will be ready at the end of 2022, and a very polished replacement mid-2023. For more details on this, see this blog post by Henry Schreiner.

### Moving to `setuptools`

For projects that only use `numpy.distutils` for historical reasons, and do not actually use features beyond those that `setuptools` also supports, moving to `setuptools` is likely the solution which costs the least effort. To assess that, there are the `numpy.distutils` features that are not present in `setuptools`:

- Nested `setup.py` files

- Fortran build support

- BLAS/LAPACK library support (OpenBLAS, MKL, ATLAS, Netlib LAPACK/BLAS, BLIS, 64-bit ILP interface, etc.)

- Support for a few other scientific libraries, like FFTW and UMFPACK

- Better MinGW support

- Per-compiler build flag customization (e.g. -O3 and SSE2 flags are default)

- a simple user build config system, see [site.cfg.example](https://github.com/numpy/numpy/blob/master/site.cfg.example)

- SIMD intrinsics support

The most widely used feature is nested `setup.py` files. This feature will likely be ported to `setuptools` (see gh-18588 for status). Projects only using that feature could move to `setuptools` after that is done. In case a project uses only a couple of `setup.py` files, it also could make sense to simply aggregate all the content of those files into a single `setup.py` file and then move to `setuptools`. This involves dropping all `Configuration` instances, and using `Extension` instead. E.g.,:

    from distutils.core import setup
    from distutils.extension import Extension
    setup(name='foobar',
          version='1.0',
          ext_modules=[
              Extension('foopkg.foo', ['foo.c']),
              Extension('barpkg.bar', ['bar.c']),
              ],
          )

For more details, see the setuptools documentation

## Interaction of `numpy.disutils` with `setuptools`

It is recommended to use `setuptools < 60.0`. Newer versions may work, but are not guaranteed to. The reason for this is that `setuptools` 60.0 enabled a vendored copy of `distutils`, including backwards incompatible changes that affect some functionality in `numpy.distutils`.

If you are using only simple Cython or C extensions with minimal use of `numpy.distutils` functionality beyond nested `setup.py` files (its most popular feature, see `Configuration`), then latest `setuptools` is likely to continue working. In case of problems, you can also try `SETUPTOOLS_USE_DISTUTILS=stdlib` to avoid the backwards incompatible changes in `setuptools`.

Whatever you do, it is recommended to put an upper bound on your `setuptools` build requirement in `pyproject.toml` to avoid future breakage - see For downstream package authors.

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