User:Churchyard/python-default-macros

Default Python version macros

For situations when an application (i.e. not a library) is compatible with both Python 3 and Python 2, the default Python version should be used. Depending on Fedora release number the default Python version might differ. For packagers' convenience and better spec readability, the following set of macros is provided:

Macro	Fedora >= 22	Fedora <= 21
python_default_version	3	2
__python_default	%{__python3}	%{__python2}
python_default_sitelib	%{python3_sitelib}	%{python2_sitelib}
python_default_sitearch	%{python3_sitearch}	%{python2_sitearch}
python_default_devel	python3-devel	python2-devel
python_default_prefix	python3-	python-
python_default_prefix_only3	python3-	(empty string)

Note: The Fedora release since when Python 3 is the default might change.

Example spec file using this approach:

Name:           fooapp
Version:        1.0.0
Release:        1%{?dist}
Summary:        This is just an example
License:        MIT
URL:            http://example.com/
Source0:        http://pypi.python.org/packages/source/f/%{name}/%{name}-%{version}.tar.gz
BuildArch:      noarch

# python3-devel or python2-devel
BuildRequires:  %{python_default_devel}

# python3-setuptools or python-setuptools
BuildRequires:  %{python_default_prefix}setuptools

# python3-pytest or pytest
BuildRequires:  %{python_default_prefix_only3}pytest

# Unfortunately with weird package names, we have to do if/else
%if %{python_default_version} > 2
BuildRequires:  python3-cairo
Requires:       python3-cairo
%else
BuildRequires:  pycairo
Requires:       pycairo
%endif

%description
This is just an example

%prep
%setup -q

# Change the shebangs if necessary
# You might need to use a different regex depending on the project
find -name '*.py' | xargs sed -i '1s|^#!python|#!%{__python_default}|'

%build

# Use the default Python interpreter
%{__python_default} setup.py build

%install

# Use the default Python interpreter
%{__python_default} setup.py install --skip-build --root %{buildroot}

%files
%doc README.rst LICENSE
%{_bindir}/%{name}

# Files will end up in proper locations
%{python_default_sitelib}/%{name}
%{python_default_sitelib}/%{name}-%{version}-py?.?.egg-info

%changelog
...

This package will use Python 3 (or 2) on Fedora releases where Python 3 (or 2) is the default without unnecessary if/else bloat. Useful when you build RPMs for multiple targets from one spec - for example on Copr.