Current File : //usr/share/doc/python3-setuptools/build_meta.rst
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Build System Support
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What is it?
-------------
Python packaging has come `a long way <https://bernat.tech/posts/pep-517-518/>`_.
The traditional ``setuptools`` way of packaging Python modules
uses a ``setup()`` function within the ``setup.py`` script. Commands such as
``python setup.py bdist`` or ``python setup.py bdist_wheel`` generate a
distribution bundle and ``python setup.py install`` installs the distribution.
This interface makes it difficult to choose other packaging tools without an
overhaul. Because ``setup.py`` scripts allowed for arbitrary execution, it
proved difficult to provide a reliable user experience across environments
and history.
`PEP 517 <https://www.python.org/dev/peps/pep-0517/>`_ therefore came to
rescue and specified a new standard to
package and distribute Python modules. Under PEP 517:
a ``pyproject.toml`` file is used to specify what program to use
for generating distribution.
Then, two functions provided by the program, ``build_wheel(directory: str)``
and ``build_sdist(directory: str)`` create the distribution bundle at the
specified ``directory``. The program is free to use its own configuration
script or extend the ``.toml`` file.
Lastly, ``pip install *.whl`` or ``pip install *.tar.gz`` does the actual
installation. If ``*.whl`` is available, ``pip`` will go ahead and copy
the files into ``site-packages`` directory. If not, ``pip`` will look at
``pyproject.toml`` and decide what program to use to 'build from source'
(the default is ``setuptools``)
With this standard, switching between packaging tools becomes a lot easier. ``build_meta``
implements ``setuptools``' build system support.
How to use it?
--------------
Starting with a package that you want to distribute. You will need your source
scripts, a ``pyproject.toml`` file and a ``setup.cfg`` file::
~/meowpkg/
pyproject.toml
setup.cfg
meowpkg/__init__.py
The pyproject.toml file is required to specify the build system (i.e. what is
being used to package your scripts and install from source). To use it with
setuptools, the content would be::
[build-system]
requires = ["setuptools", "wheel"]
build-backend = "setuptools.build_meta"
The ``setuptools`` package implements the ``build_sdist``
command and the ``wheel`` package implements the ``build_wheel``
command; both are required to be compliant with PEP 517.
Use ``setuptools``' :ref:`declarative config <declarative config>` to
specify the package information::
[metadata]
name = meowpkg
version = 0.0.1
description = a package that meows
[options]
packages = find:
Now generate the distribution. To build the package, use
`PyPA build <https://pypa-build.readthedocs.io/en/latest/>`_::
$ pip install -q build
$ python -m build
And now it's done! The ``.whl`` file and ``.tar.gz`` can then be distributed
and installed::
dist/
meowpkg-0.0.1.whl
meowpkg-0.0.1.tar.gz
$ pip install dist/meowpkg-0.0.1.whl
or::
$ pip install dist/meowpkg-0.0.1.tar.gz
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