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openSUSE:Packaging Python

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The Packaging Python is a step by step introduction on how to build Python software packages for openSUSE and others using the openSUSE Build Service.

The fast and automated way

Lets suppose you want to package zope interface and you don't know how it is named exactly or where to download from. First of all, you can search for the exact name on PyPI. The name of a package is the in the URL and in the pip install instruction at the top of the page: pip install zope.interface.

Now download the source tarball automatically with py2pack:

$ py2pack fetch zope.interface
downloading package zope.interface-5.4.0...
from https://files.pythonhosted.org/packages/source/z/zope.interface/zope.interface-5.4.0.tar.gz

As a next step you may want to generate a package recipe for your distribution. For RPM-based distributions, you want to generate a spec file named python-zopeinterface.spec. The metadata for the spec file is read from the source archive you just downloaded:

$ py2pack generate zope.interface -f python-zope.interface.spec

The source tarball and package recipe is all you need to generate the RPM file. This final step may depend on which distribution you use. Again, for openSUSE (and by using the openSUSE Build Service), the complete recipe becomes:

$ osc mkpac python-zope.interface
$ cd python-zope.interface
$ py2pack fetch zope.interface
$ py2pack generate zope.interface -f python-zope.interface.spec
$ vi *.spec
BuildRequires: python-setuptools
ZZ
$ osc build
$ osc vc
$ osc add *
$ osc commit

The first line uses osc, the Build Service command line tool to generate a new package (preferrably in your Build Service home project). The py2pack steps are known already.

It is always a good idea to review all the dependencies specified in the spec file accordingly to the upstream manifest and requirements, e.g. dropping the %{python_module devel} dependency in a case where the package does not compile anything, or adding python-setuptools if needed. Sometimes the test requirements are specified in upstream's setup.py as extra [test] or similar, which are converted to Recommends: python-foo tags by py2pack. You need to change them to BuildRequires: %{python_module foo} to be able to actually run the tests at build time. However, most of the time, we don't need static linters or code coverage tools despite specified upstream, such as mypy, coverage, pytest-cov, flake8, or black. Just omit installing and running those.

Finally, the package is tested (built locally), a .changes (package changelog) file is generated (with 鈥榦sc vc鈥) and the result is sent back to the Build Service for public consumption. However, depending on the Python module, you may have to adapt the generated spec file slightly. Py2pack is quite clever and tries to auto-generate as much as it can, but it depends on the metadata that the module provides. Thus, bad metadata implies mediocre results.

To get further help about py2pack usage, issue the following command:

$ py2pack help

Often, the first run of 'osc build' will fail with build error messages, due to missing python modules. Look for the keyword 'import', this should give you a hint, what needs to be added to the 'BuildRequires:' (and possibly 'Requires:', if the import also happens in the installed package) of you spec-file.


Hints on how to package Python modules manually

Manual packaging from scratch is discouraged since we have tools to do that (see above). If you insist on having fun, please consider any package spec file in devel:languages:python. python-autobahn, python-black or python-Twisted are few examples.

In general we are using single-spec packaging for any Distribution package, which provides modules importable by other packages.

What is single-spec?

'Single-spec' (or 'Singlespec') is an approach for packaging multiple variants of a Python module from a single source spec file. The variants are based on the available Python 'flavors'. These used to be 'python2' and 'python3', but has been extended to multiple variants of Python 3. This means that Tumbleweed by default builds for the flavors 'python36', 'python38', 'python39' (but not 'python2' anymore), while Leap 15 has 'python2' and 'python3' as its default build set. One of the 'python3X' flavors, currently 'python38', in Tumbleweed is also at the same time the primary 'python3' flavor.

The set of available flavors is defined by python-rpm-macros. You need to define

BuildRequires:  python-rpm-macros

Compatibility shim

If your packages are targeted for anything other than Leap 15 or newer, the spec file must include a redefinition of %python_module macro.

%{?!python_module:%define python_module() python-%{**} python3-%{**}}

Build set and naming policy

SUSE has a policy for names of Python module packages. A module is to Python what shared libraries are to C - a piece of code that doesn't work by itself, but provides functionality to other Python programs.

All Python module packages, whether pure Python or C-based, should be called python-modulename. modulename should be the name of this module on the Python Package Index.

Previously, Python packages have been named after directories in the site-packages hierarchy. Often, this was an arbitrary choice, several modules install more than one directory there. Also, the Python universe includes modules that share the same directory name (search for "daemon" on PyPI) and it was not always easy to find out the right package name. Furthermore, the new approach has several advantages:

This policy doesn't apply to end-user applications that are not designed and planned to be used as libraries - so if you're packaging something that is going to have an icon in the application menu, you should just call the package by its normal name (as found on the Python Package Index), and don't generate subpackages for multiple flavors.

There are some corner cases as to what is an application and what is a module - for example, many modules come with simple command-line tools that allow you to use a subset of their functionality directly.

The rule of thumb is this:

  • If this package is going to be a dependency of some other Python application, use single-spec and apply the naming policy,
  • otherwise keep it just as the module name and specify all dependencies to come from the primary python flavor (python3).

Similarly, this policy doesn't apply to jupyter kernels, extensions, and similar packages that are not designed and planned to be used as libraries. If they are meant to be used exclusively within the confines of a jupyter environment, they should be called jupyter-modulename instead of python-modulename, where modulename is still the the name of this module on the Python Package Index. Such packages must also provide the python3-modulename package if they contain python code. Conversely, packages that are primarily python packages but provide jupyter interfaces should either have the python3 version provide jupyter-modulename, or split out the components in the jupyter data directories into their own jupyter-modulename subpackage.

Source URLs

For packages that are available from PyPI, the correct Source URL is the following:

https://files.pythonhosted.org/packages/source/t/tox/tox-%{version}.tar.gz

The preferred hostname is files.pythonhosted.org. All other hostnames (like pypi.io, pypi.org, pypi.python.org) eventually redirect to it. In order to ease this transition you can put in the bellow mentioned link and it will be automatically converted to the proper format by spec-cleaner tool.

The link you get from PyPI will point to some sort of hash, e.g., https://files.pythonhosted.org/packages/99/20/2fd208e75c05975bf6436258f469aa233045b93d195cdb442045de0923cc/tox-2.7.0.tar.gz. We don't want that. The "semantic URL" is still available:
/packages/source/<first letter>/<full name>/<full name>-<version>.<extension>

In some cases, packages are only distributed through PyPI as wheels. These are files with a .whl. extension. In these cases, either the wheels can be packaged manually, or another upstream source can be used if available (such as from github, see below). The path to the wheel file is of the form:

/packages/<python version>/<first letter>/<full name>/<full name>-<version>-<python version>-<abi>-<platform>.whl.

python version is the specific versions of python the wheel supports, such as py3 for python3-only and py2.py3 for both. Note that this appears twice in the URL, and they must match. abi is the architecture-specific abi. Only wheels with the none abi can be used, since others contain pre-compiled libraries. platform is the particular operating system supported. This must be any, since again anything else contains pre-compiled libraries. Some example of full source URLs for wheels are:

https://files.pythonhosted.org/packages/py2.py3/b/bqplot/bqplot-%{version}-py2.py3-none-any.whl
https://files.pythonhosted.org/packages/py3/i/imatlab/imatlab-%{version}-py3-none-any.whl

For some packages, particularly jupyter kernels or extensions, wheels contains important files the source distribution is missing. In these cases, the use of wheels is preferred. You can check for such files by opening the wheel file (it is just a zip file, if you archive reader can't open it you can change the extension) and look for files in the etc or usr directory.

However, in some situations important files are missing from the PyPI archive or wheel. For example they may be missing tests or license files. Such issues should be reported upstream. If it is a single file, like a license file for licenses that require one, and the upstream has a source such as github that includes that file, it is possible to include it and set the source URL to be the "raw" version of the file while waiting for upstream to provide a proper fix. For example:

https://raw.githubusercontent.com/imatlab/imatlab/v%{version}/LICENSE.txt

However, for packages where many files or whole directories are missing, particularly tests, the upstream source should be used. For github, that source is of the form:

https://github.com/numpy/numpy/archive/v1.16.2.tar.gz#/numpy-1.16.2.tar.gz

The #/numpy-1.16.2.tar.gz part at the end is important. If that is left off, the openSUSE:Factory source validator will download a file named v1.16.2.tar.gz instead of numpy-1.16.2.tar.gz, which will cause the source validation to fail.

BuildRequires

BuildRequires are not conditional and apply for the whole spec file. There is no such thing as "if I build for Python 2, I require package foo"; you simply require all packages for all variants.

To automatically require a python package for all flavors of python within the build set, use the %python_module macro.

BuildRequires: %{python_module setuptools}
BuildRequires: %{python_module py >= 1.4}

Note that the version requirement goes inside the %python_module call.

This is not intended for Requires tag. The %python_module macro is only for BuildRequires, as it specifies all flavors at once. Requires: should only specify packages for the particular flavor and is rewritten by %python_subpackages.

If you only need the package for one flavor of python, simply don't use the macro and state the dependencies directly.

BuildRequires: python2-enum34
BuildRequires: python3-astroid

openSUSE Tumbleweed has removed the majority of python2 packages and does not include Python2 into the buildset anymore. It defines the equivalent of osc build --without python2 by default. So if you still need to support building python2 packages for older distributions, you can exclude the requirements for Tumbleweed by

%bcond_without python2
%if %{with python2}
BuildRequires: python2-enum34
%endif

If you need a package under certain conditions, use RPM boolean dependencies. For projects inheriting their project configuration from openSUSE:Factory or devel:languages:python:backports, you can reference the Python version of the expanded flavor itself by using the pseudo %python macro (don't define %python anywhere else):

BuildRequires: %{python_module aiocontextvars >= 0.2.2 if %python-base < 3.7}

If you need to BuildRequire "python", you can use %pythons:

BuildRequires: %{pythons}
Warning: This macro works only on openSUSE Leap 15.0 and newer. %pythons and %python_module do not only need a recent python-rpm-macros package but also need the corresponding definition in the OBS project configuration, either directly or by inheritance.

Automatic Runtime Requirements Determination

Python dependencies can be automatically determined by adding the following right after the BuildRequires list:

BuildRequires: python-rpm-generators
%{?python_enable_dependency_generator}

Correct runtime dependencies will be generated from the egg/dist metadata.
The package python-rpm-generators offers some more useful macros, see project page on Github

Any build time and test dependencies still have to be specified manually with BuildRequires.


Requires, Provides and similar

In many cases, you don't need to do anything. The single-spec rewriter will convert your Requires to match the generated package. Only make sure the Requires content really matches up setup.py or requirements.txt and there is nothing missing.

Warning: In particular, do not use %python_module for Requires.

Python package names in tags Requires, Requires(pre) and all other scriptlet runtime requirements, Provides, Recommends, Suggests, Obsoletes, Conflicts, Supplements, and Enhances are automatically converted to the correct flavor in the subpackage declarations autogenerated by %python_subpackages.

If the requirement or capability name starts with "python-", with the default python flavor ("python38-" in Tumbleweed, "python3-" in older distributions), or with the same python prefix as your package name (so "python3-bar" in package "python3-foo"), then the python name is changed to match that of the generated package. This also works for "python" itself.

If you want to prevent rewriting of the name, mask it behind a macro (e.g. with the use of %oldpython as shown below.)

The converter takes into account the packageand expression, and %requires_ge and %requires_eq macros. However, support for these must be coded explicitly. If you find an expression that is not converted, please either post it on the packaging ML or file a bug against python-rpm-macros. RPM's boolean requirements are not supported yet.

Requirements specific for one python flavor

You can specify that some packages should only be included for some python flavors, by wrapping them in conditionals using the %python_flavor variable

Requires: python-idna
%if "%{python_flavor}" == "python2"
Requires: python2-enum34
%endif

As a shortcut, for every flavor, there is a %ifpython macro: %ifpython2, %ifpython3 or %ifpypy3.

%ifpython2
Requires: python2-enum34
%endif

Note that the shortcuts must not be nested in other conditionals, otherwise you can get "%endif without %if" error message. If you need to nest conditionals, use the %python_flavor conditional.

Warning: This works by copying the %ifpython sections to the generated subpackage definitions, where they are evaluated for conditional application. Subpackages have their own runtime requirements, file lists and %pre/%post/etc. scriptlets. The scripts from the %prep, %build, %install, %check sections and global tags such as BuildRequires are not subpackage specific. Do not use %ifpython for these.


Testing for the python3 flavor through %ifpython3 or %if "%{python_flavor}" == "python3" is deprecated. These conditionals do not work for repositories with multple flavors for Python 3, i.e. they will not apply for any flavor named python36, python38, python39, and so on. If you have a section that should only apply for one of the generated Python 3 packages, use

%if "%{python_flavor}" == "python3" || "%{python_provides}" == "python3"
Provides: foo
%endif

Obsoleting and Providing old symbols

The following sequence:

Obsoletes: python-distribute < %{version}
Provides:  python-distribute = %{version}

would mean that your python2-package will obsolete/provide python2-distribute and your python3-package will obsolete/provide python3-distribute and your pypy3 package will obsolete/provide pypy3-distribute.
Often, this is not what you want.

First of all, in many cases, this is only applicable for Python 2, so the sequence should be wrapped in %ifpython2 conditional.

Second, you will note that neither package obsoletes/provides python-distribute.
Here is how you do that:

%define oldpython python
%ifpython2
Obsoletes: %{oldpython}-distribute < %{version}
Provides:  %{oldpython}-distribute = %{version}
%endif


%python_module in Provides

If you are creating a subpackage that will be common for all flavors (could be a -doc subpackage), sometimes you need to provide a symbol for all flavors.

E.g., your package python-foo-doc should also provide python2-foo-doc, python3-foo-doc etc.

In such case, you use the %python_module macro:

%package -n python-foo-doc
Provides: %{python_module foo-doc = %{version}}

This is also the one case where you could use %python_module in Requires.

(See below on declaring packages with -n to prevent autogeneration.)


%python_subpackages

Easy enough: place the %python_subpackages macro on a separate line at the end of the spec preamble (the part that ends where your package's %description begins).

Provides: pylint
BuildRoot: %{tmproot}/blabla
BuildArch: noarch

%python_subpackages

%description

This macro emits all the subpackage descriptions, %files and scriptlet sections for the autogenerated parts.


Subpackage declarations

Subpackages are converted automatically. If you have a subpackage %package foo, singlespec will create python3-yourpackage-foo and all the rest from it.

If you want to prevent this, use %package -n %{name}-foo. Or the full name, %package -n python-yourpackage-foo. This will ensure that the subpackage will be skipped.

This also means that packages named %package -n yourpackage-python will not be processed. There will be a mechanism for these in the future.

Common documentation packages

It is very common that the shipped documentation and probably included examples are quite big and should be in a separate sub-package. The package could have - for example - these sections:

%package -n %{name}-doc
Summary:        Documentation files for %name
Group:          Documentation/Other

%description -n %{name}-doc
HTML Documentation and examples for %name.

%files -n %{name}-doc
%doc examples docs/_build/html/

Build macros

For building the packages use %python_build.
For installing the packages use %python_install.

These macros already contain the usual options (--root, --prefix), so in the typical case, you don't need to supply any options. If you have something specific, you can add it: %python_build --enable-specific-feature.

If you set environment variables, export them first:

export CFLAGS="-fwrapv"
%python_build

For any other commands, you can use %python_exec and %python_expand. That is also a good way to run pythonic executables. For example:

%check
%python_exec setup.py extracommand
%python_expand ./make PYTHON=$python
%python_expand PYTHONPATH=%{buildroot}%{$python_sitelib} my-alternative-cloned-entrypoint-%{$python_version}

%python_expand

For anything more complicated than executing all the interpreters, use the %python_expand macro. This will repeatedly expand the %{$python}, %{$python_sitelib} etc. strings to the currently used flavor.

%python_expand rm -r %{buildroot}%{$python_sitelib}/file.txt

results in (apart from some build dir manipulations):

rm -r %{buildroot}%{python2_sitelib}/file.txt
rm -r %{buildroot}%{python3_sitelib}/file.txt
rm -r %{buildroot}%{pypy3_sitelib}/file.txt

IMPORTANT: you can use %python_expand to replace macro definitions, but make sure you use, e.g., %{$python_sitelib}, with the $ sign.
If you use plain %{python_sitelib}, the macro will be expanded before %python_expand can modify it.

A common use for %python_expand is with fdupes, as in:

%python_expand %fdupes %{buildroot}%{$python_sitelib}/mymodule

You can use multiline %python_expand if you enclose the lines in {}. The only technical limitation is that the first line must not be empty (but can be a comment starting with #):

%{python_expand # this will expand the following section
%$python_install
mv %{buildroot}%{_bindir}/exename %{buildroot}%{_bindir}/exename-%{$python_bin_suffix}
}

This is eg useful when running tests and some pre-step is needed:

%check
%{python_expand rm -rf .testrepository
$python -m unittest discover -v                                                                                                                                                                                                                                                               
}

Naming flavor-specific files

Executables specific to a particular flavor should use %python_bin_suffix instead of %python_version for names. This expands to %python_version for CPython, pp%{python_version} for PyPy. If we support Jython, it will get a specific bin_suffix too.

Build directories specific to a particular flavor should use %python_prefix. This expands to the flavor name.


Filelists

If your package is called python-something (that is, the name prefix is "python" and not a specific flavor), you must mark your %files sections with %{python_files} macro.

%files %{python_files}
%{python_sitelib}/foo

%files %{python_files plugins}
%{python_sitelib}/foo-plugins

You can use %ifpython2 and similar to conditionally include some files only in some flavors. In addition, you can use shorthands:

%files %{python_files}
%{python_sitelib}/foo
%{python_sitelib}/foorun.py*
%pycache_only %{python_sitelib}/__pycache__

Use %pycache_only or %ifpycache to mark __pycache__ directories.


Executables

For multi-flavor packages which carry executables (Python setuptools calls them entry-points) you need to ensure that they don't create file conflicts.

Some packages still rely on the %python3_only syntax which ensured the binary was carried over only to the specific version. This approach albeit shorter has a drawback of not working in multi-python-interpreter environment and as such we deprecate its usage.

update-alternatives

Sometimes it is useful to let the user switch the unversioned executable name to one version of the package or another.

update-alternatives allows you to switch other things (usually man pages) along with executables.

As a prerequisite, you need to have version-specific file names available -- that is, for every file you provide, file-%python_bin_suffix should exist for all flavors. (for manpage.1, the appropriate name is manpage-%python_bin_suffix.1)

First, you need to set up the alternatives in %install section.

  • If you're using %python_clone to create the executable, simply pass -a option: %python_clone -a %{buildroot}%{_bindir}/executable
  • If not, and the file in question is %{_bindir}/something, call %prepare_alternative something
  • If the file is not in %{_bindir}, you have to specify the path: %prepare_alternative -t /path/to/file file. The path is without %buildroot

Second, create the appropriate %post and %postun sections. Make sure that you have the proper requirements:

Requires(post):   update-alternatives
Requires(postun):  update-alternatives

Then use %python_install_alternative and %python_uninstall_alternative respectively.

%post
%python_install_alternative exename

%postun
%python_uninstall_alternative exename

Third, mention the alternative, unversioned, in file list

%python_alternative %{_bindir}/exename

You can examine a full spec file at [1].

Grouped alternatives

The update-alternatives system allows for multiple files in the same group, to be switched together. This is useful if you want to install an executable along with its manpage, or multiple executables belonging to the same function group.

To make use of this, simply specify the files as multiple arguments to %python_install_alternative:

%{python_install_alternative pylint pylint.1 epylint epylint.1}

The macro can recognize manpage names and handle them correctly, but the first arguments needs always to the an executable. Or you can specify a full path to the file in question.

The first argument to %python_install_alternative is the group name. This is the only argument for %python_uninstall_alternative; you uninstall the whole group by the one name.


Decision whether to build for single or multiple Python versions

Python2 only (Leap)

Non-singlespec packages that only exist for Python 2 should be left as is. New packages should be called python2-foo. Old packages should be left as python-foo, but you should add Provides: python2-foo. You should also make sure that all BuildRequires and Requires are for "python2" and "python2-foo".

Python 3 (Leap and Tumbleweed)

Packages that only exist for a single Python 3 flavor (apps) can omit the single-spec system, or they can use single-spec with a single flavor in the build set. Modules should be single-spec with all possible flavors. See #Build set and naming policy for a distinction between apps and modules. The definitions should be made at the top of the spec-file.

For apps:

  • %define pythons python3

For modules:

  • Use %define skip_python2 1 so that the Leap does not try to build python2.
  • Skip all flavors which are not supported, e.g. %define skip_python36 1 for anything in the NumPy ecosystem.

Conditionals on Python versions

If you need to differentiate between python versions you can use the %python_version_nodots macro, which expands to the Python major and minor version of the currently auto-generated flavor package, with the dot removed.

For example:

%if %python_version_nodots < 39
Requires: python-importlib_resources
%endif

If you need to determine the version of a specific general provider, use the flavored variant of the macro, e.g.:

Macros Example
%python2_version_nodots 27
%python3_version_nodots 38



Common Gotchas

Things to look out for (which can also get your submission declined):

  1. If the %python_module redefinition is present, check that it has "python-%{**}" and not "python-%1"
  2. use %python_module for BuildRequires
  3. do NOT use %python_module for Requires
  4. make sure %python_subpackages macro is present
  5. %files sections must be marked as %files %{python_files}
  6. in %python_expand, make sure you use %{$python_} macros instead of %python_ macros
  7. use %python_bin_suffix instead of %python_version for distinguishing executables or build directories
  8. don't use %ifpython3 or %python3_only, if the line or code block should apply for the primary Python 3 flavor (exlusively or also for possible additional flavors).

Running tests

The python code is not really compiled like C applications. As such it is really easy to distribute something that does not work at all. In order to prevent this all applications must run and pass their tests unless upstream is providing none themselves.

The easiest way to run tests is using the unittest discover mode, which we have a macro for:

%pyunittest -v

This of course only works, if the package supports regular python unittests. If this call does not work one has to dig around checking various files in the development repository like .travis.yml or tox.ini.

To run pytest, the macros %pytest and %pytest_arch can be used.

All Macros

The full documentation for all macros defined for singlespec can be found at the GitHub page for python-rpm-macros package.