5. Creating Built Distributions¶
This document is being retained solely until the setuptools documentation at https://setuptools.readthedocs.io/en/latest/setuptools.html independently covers all of the relevant information currently included here.
A “built distribution” is what you’re probably used to thinking of either as a “binary package” or an “installer” (depending on your background). It’s not necessarily binary, though, because it might contain only Python source code and/or byte-code; and we don’t call it a package, because that word is already spoken for in Python. (And “installer” is a term specific to the world of mainstream desktop systems.)
A built distribution is how you make life as easy as possible for installers of your module distribution: for users of RPM-based Linux systems, it’s a binary RPM; for Windows users, it’s an executable installer; for Debian-based Linux users, it’s a Debian package; and so forth. Obviously, no one person will be able to create built distributions for every platform under the sun, so the Distutils are designed to enable module developers to concentrate on their specialty—writing code and creating source distributions—while an intermediary species called packagers springs up to turn source distributions into built distributions for as many platforms as there are packagers.
Of course, the module developer could be their own packager; or the packager could be a volunteer “out there” somewhere who has access to a platform which the original developer does not; or it could be software periodically grabbing new source distributions and turning them into built distributions for as many platforms as the software has access to. Regardless of who they are, a packager uses the setup script and the bdist command family to generate built distributions.
As a simple example, if I run the following command in the Distutils source tree:
then the Distutils builds my module distribution (the Distutils itself in this case), does a “fake” installation (also in the build directory), and creates the default type of built distribution for my platform. The default format for built distributions is a “dumb” tar file on Unix, and a simple executable installer on Windows. (That tar file is considered “dumb” because it has to be unpacked in a specific location to work.)
Thus, the above command on a Unix system creates Distutils-1.0. plat .tar.gz ; unpacking this tarball from the right place installs the Distutils just as though you had downloaded the source distribution and run python setup.py install . (The “right place” is either the root of the filesystem or Python’s prefix directory, depending on the options given to the bdist_dumb command; the default is to make dumb distributions relative to prefix .)
Obviously, for pure Python distributions, this isn’t any simpler than just running python setup.py install —but for non-pure distributions, which include extensions that would need to be compiled, it can mean the difference between someone being able to use your extensions or not. And creating “smart” built distributions, such as an RPM package or an executable installer for Windows, is far more convenient for users even if your distribution doesn’t include any extensions.
The bdist command has a —formats option, similar to the sdist command, which you can use to select the types of built distribution to generate: for example,
python setup.py bdist --format=zip
would, when run on a Unix system, create Distutils-1.0. plat .zip —again, this archive would be unpacked from the root directory to install the Distutils.
The available formats for built distributions are:
Python package guidelines
This document covers standards and guidelines on writing PKGBUILDs for Python software.
Package naming
For Python 3 library modules, use python-modulename . Also use the prefix if the package provides a program that is strongly coupled to the Python ecosystem (e.g. pip or tox). For other applications, use only the program name.
Architecture
A Python package that contains C extensions is architecture-dependent. Otherwise it is most likely architecture-independent.
Packages built using setuptools define their C extensions using the ext_modules keyword in setup.py .
Source
Download URLs linked from the PyPI website include an unpredictable hash that needs to be fetched from the PyPI website each time a package must be updated. This makes them unsuitable for use in a PKGBUILD. PyPI provides an alternative stable scheme: PKGBUILD#source source=() array should use the following URL templates:
Note that a custom _name variable is used instead of pkgname since Python packages are generally prefixed with python- . This variable can generically be defined as follows:
Installation methods
Python packages are generally installed using language-specific package manager such as pip, which fetches packages from an online repository (usually PyPI, the Python Package Index) and tracks the relevant files.
However, for managing Python packages from within PKGBUILD s, one needs to «install» the Python package to the temporary location $pkgdir/usr/lib/python /site-packages/$pkgname .
For Python packages using standard metadata to specify their build backend in pyproject.toml , this can most easily achieved using python-build and python-installer . Old packages might fail to specify that they use setuptools, and only offer a setup.py that has to be invoked manually.
Note: Dependencies from the package’s metadata must be defined in the depends array otherwise they will not be installed.
Standards based (PEP 517)
A standards based workflow is straightforward: Build a wheel using python-build and install it to $pkgdir using python-installer :
makedepends=(python-build python-installer python-wheel) build() < cd "$_name-$pkgver" python -m build --wheel --no-isolation >package() < cd "$_name-$pkgver" python -m installer --destdir="$pkgdir" dist/*.whl >
- —wheel results in only a wheel file to be built, no source distribution.
- —no-isolation means that the package is built using what is installed on your system (which includes packages you specified in depends ), by default the tool creates an isolated virtual environment and performs the build there.
- —destdir=»$pkgdir» prevents trying to directly install in the host system instead of inside the package file, which would result in a permission error
- —compile-bytecode=. or —no-compile-bytecode can be passed to installer , but the default is sensibly picked, so this should not be necessary.
Warning: Skipping build and putting the .whl file in your source array is discouraged in favor of building from source, and should only be used when the latter is not a viable option (for example, packages which only come with wheel sources, and therefore cannot be built from source).
Warning: If your package is a VCS package ( python-…-git ), include the command git -C «$/$» clean -dfx in your prepare function. This removes stale wheels along with other build artifacts, and helps prevent issues further down the road. See also upstream issues for setuptools and Poetry.
setuptools or distutils
If no pyproject.toml can be found or it fails to contain a [build-system] table, it means the project is using the old legacy format, which uses a setup.py file which invokes setuptools or distutils. Note that while distutils is included in Python’s standardlib, having setuptools installed means that you use a patched version of distutils.
makedepends=(‘python-setuptools’) # unless it only requires distutils build() < cd "$_name-$pkgver" python setup.py build >package()
- —root=»$pkgdir» works like —destdir above
- —optimize=1 compiles optimized bytecode files (.opt-1.pyc) so they can be tracked by pacman instead of being created on the host system on demand.
- Adding —skip-build optimizes away the unnecessary attempt to re-run the build steps already run in the build() function, if that is the case.
If the resulting package includes executables which import the deprecated pkg_resources module, then setuptools must be additionally specified as a depends in the split package_*() functions; alternatively, if the PKGBUILD only installs the Python package for a single version of Python, setuptools should be moved from makedepends to depends .
Some packages try to use setuptools and fall back to distutils if setuptools could not be imported. In this case, setuptools should be added as a makedepends , so that the resulting Python metadata is better.
If a package needs setuptools to be built due to including executables (which is not supported by distutils), but only imports distutils, then building will raise a warning, and the resulting package will be broken (it will not contain the executables):
/usr/lib/python3.8/distutils/dist.py:274: UserWarning: Unknown distribution option: 'entry_points' warnings.warn(msg)
An upstream bug should be reported. To work around the problem, an undocumented setuptools feature can be used:
# fails because of distutils python setup.py build # works by using a setuptools shim python -m setuptools.launch setup.py build
If a package uses python-setuptools-scm , the package most likely will not build with an error such as:
LookupError: setuptools-scm was unable to detect version for /build/python-jsonschema/src/jsonschema-3.2.0. Make sure you're either building from a fully intact git repository or PyPI tarballs. Most other sources (such as GitHub's tarballs, a git checkout without the .git folder) don't contain the necessary metadata and will not work.
To get it building SETUPTOOLS_SCM_PRETEND_VERSION has to be exported as an environment variable with $pkgver as the value:
export SETUPTOOLS_SCM_PRETEND_VERSION=$pkgver
Check
Warning: Avoid using tox to run testsuites as it is explicitly designed to test repeatable configurations downloaded from PyPI while tox is running, and does not test the version that will be installed by the package. This defeats the purpose of having a check function at all.
Most Python projects providing a testsuite use nosetests or pytest to run tests with test in the name of the file or directory containing the testsuite. In general, simply running nosetests or pytest is enough to run the testsuite.
If there is a compiled C extension, the tests need to be run using a $PYTHONPATH , that reflects the current major and minor version of Python in order to find and load it.
check()< cd "$pkgname-$pkgver" local python_version=$(python -c 'import sys; print("".join(map(str, sys.version_info[:2])))') # For nosetests PYTHONPATH="$PWD/build/lib.linux-$CARCH-cpython-$" nosetests # For pytest PYTHONPATH="$PWD/build/lib.linux-$CARCH-cpython-$" pytest > Some projects provide setup.py entry points for running the test. This works for both pytest and nosetests .
Tips and tricks
Discovering detached PGP signatures on PyPI
If detached PGP signatures for a given Python sdist tarball exist, they should be used to verify the tarball. However, the signature files do not show up directly in the files download section of any given project on pypi.org. To discover the sdist tarballs and their potential signature files, it is possible to use this service to get an overview per project: https://pypi.debian.net/
Using python version
Sometimes during preparing, building, testing or installation it is required to refer to the system’s major and minor Python version. Do not hardcode this (e.g. 3.9 or 3.10 ) and instead use a call to the Python interpreter to retrieve the information and store it in a local variable:
Using site-packages
Sometimes during building, testing or installation it is required to refer to the system’s site-packages directory. Do not hardcode this directory and use a call to the Python interpreter instead to retrieve the path and store it in a local variable:
Test directory in site-package
Make sure to not install a directory named just tests into site-packages (i.e. /usr/lib/pythonX.Y/site-packages/tests/ ). Python package projects using setuptools are sometimes misconfigured to include the directory containing its tests as a top level Python package. If you encounter this, you can help by filing an issue with the package project and ask them to fix this, e.g. like this.
- This page was last edited on 21 June 2023, at 09:51.
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