We currently package Python 2 and Python 3, under the Scheme variable names
python as explained in Version Numbers.
To avoid confusion and naming clashes with other programming languages, it
seems desirable that the name of a package for a Python module contains
Some modules are compatible with only one version of Python, others with
both. If the package Foo is compiled with Python 3, we name it
python-foo. If it is compiled with Python 2, we name it
python2-foo. Packages should be added when they are necessary;
we don’t add Python 2 variants of the package unless we are going to use
If a project already contains the word
python, we drop this;
for instance, the module python-dateutil is packaged under the names
python2-dateutil. If the project name
pytz), we keep it and prefix it as
Note: Currently there are two different build systems for Python packages in Guix: python-build-system and pyproject-build-system. For the longest time, Python packages were built from an informally specified setup.py file. That worked amazingly well, considering Python’s success, but was difficult to build tooling around. As a result, a host of alternative build systems emerged and the community eventually settled on a formal standard for specifying build requirements. pyproject-build-system is Guix’s implementation of this standard. It is considered “experimental” in that it does not yet support all the various PEP-517 build backends, but you are encouraged to try it for new Python packages and report any problems. It will eventually be deprecated and merged into python-build-system.
Dependency information for Python packages is usually available in the package source tree, with varying degrees of accuracy: in the pyproject.toml file, the setup.py file, in requirements.txt, or in tox.ini (the latter mostly for test dependencies).
Your mission, when writing a recipe for a Python package, is to map
these dependencies to the appropriate type of “input” (see inputs). Although the
pypi importer normally does a
good job (see Invoking guix import), you may want to check the
following check list to determine which dependency goes where.
pipinstalled per default. This is about to change, and users are encouraged to use
python-toolchainif they want a build environment for Python.
guix lint will warn if
added as native-inputs because they are generally not necessary.
propagated-inputs. They are typically defined with the
install_requireskeyword in setup.py, or in the requirements.txt file.
build-system.requiresin pyproject.toml or with the
setup_requireskeyword in setup.py—or dependencies only for testing—e.g., those in
tests_requireor tox.ini—go into
native-inputs. The rationale is that (1) they do not need to be propagated because they are not needed at run time, and (2) in a cross-compilation context, it’s the “native” input that we’d want.
Examples are the
frameworks. Of course if any of these packages is also required at
run-time, it needs to go to
inputs, for example programs or C libraries required for building Python packages containing C extensions.
extras_require), it is up to you to decide whether to add them or not, based on their usefulness/overhead ratio (see