Two incompatible versions of Python are widely used, Python 2.x and Python 3.x.

Red Hat Enterprise Linux 8 uses Python 3.6 by default. However, Python 2.7 is also provided to support existing software.

As a system administrator, you are recommended to use preferably Python 3 for the following reasons:

For developers, Python 3 has the following advantages over Python 2:

However, existing software tends to require /usr/bin/python to be Python 2. For this reason, no default python package is distributed with Red Hat Enterprise Linux 8, and you can choose between using Python 2 and 3 as /usr/bin/python, as described in Section 8.2.5, “Configuring the unversioned Python”.

System tools in Red Hat Enterprise Linux 8 use a Python version 3.6 provided by the internal platform-python package. Red Hat advises customers to use the python36 package instead.

In Red Hat Enterprise Linux 8, Python 3 is distributed as the python36 module in the AppStream repository.

To install Python 3.6 from the python36 module in AppStream, use the following procedure.

For details regarding modules, see Installing, managing, and removing user-space components.

Some software has not yet been fully ported to Python 3, and needs Python 2 to operate. Red Hat Enterprise Linux 8 allows parallel installation of Python 3 and Python 2. If you need the Python 2 functionality, install the python27 module, which is available in the AppStream repository.

To install Python 2.7 from the python27 module in AppStream, use the following procedure.

For details regarding modules, see Installing, managing, and removing user-space components.

To run Python 3, always use the python3 command. Use the version also in all other related commands, such as pip3.

Packages with add-on modules for Python 3 generally use the python3- prefix.

For example, to install the Requests module that is used for writing HTTP clients, use this procedure.

To run Python 2, always use the python2 command. Use the version also in all other related commands, such as pip2.

Packages with add-on modules for Python 2 generally use the python2- prefix.

For example, to install the Requests module that is used for writing HTTP clients, use the following procedure.

System administrators can configure the unversioned python command on the system using the alternatives command. Note that the required package, either python3 or python2, needs to be installed before configuring the unversioned command to the respective version.

A SPEC file contains instructions that the rpmbuild utility uses to build an RPM. The instructions are included in a series of sections. A SPEC file has two main parts in which the sections are defined:

For further information about SPEC files, see Packaging and distributing software.

An RPM SPEC file for Python projects has some specifics compared to non-Python RPM SPEC files. Most notably, a name of any RPM package of a Python library must always include the python3 prefix.

Other specifics are shown in the following SPEC file example for the python3-detox package. For description of such specifics, see the notes below the example.

%global modname detox                                                           1

Name:           python3-detox                                                   2
Version:        0.12
Release:        4%{?dist}
Summary:        Distributing activities of the tox tool
License:        MIT
URL:            https://pypi.io/project/detox
Source0:        https://pypi.io/packages/source/d/%{modname}/%{modname}-%{version}.tar.gz

BuildArch:      noarch

BuildRequires:  python36-devel                                                  3
BuildRequires:  python3-setuptools
BuildRequires:  python36-rpm-macros
BuildRequires:  python3-six
BuildRequires:  python3-tox
BuildRequires:  python3-py
BuildRequires:  python3-eventlet

%?python_enable_dependency_generator                                            4

%description

Detox is the distributed version of the tox python testing tool. It makes efficient use of multiple CPUs by running all possible activities in parallel.
Detox has the same options and configuration that tox has, so after installation you can run it in the same way and with the same options that you use for tox.

    $ detox

%prep
%autosetup -n %{modname}-%{version}

%build
%py3_build                                                                      5

%install
%py3_install

%check
%{__python3} setup.py test                                                      6

%files -n python3-%{modname}
%doc CHANGELOG
%license LICENSE
%{_bindir}/detox
%{python3_sitelib}/%{modname}/
%{python3_sitelib}/%{modname}-%{version}*

%changelog
...

In a SPEC file, always use the macros below rather than hardcoding their values.

In macro names, always use python3 or python2 instead of unversioned python.

When packaging a Python project, make sure that, if present, the following directories are included in the resulting RPM:

From these directories, the RPM build process automatically generates virtual pythonX.Ydist provides, for example python3.6dist(detox). These virtual provides are used by packages that are specified by the %python_enable_dependency_generator macro.

In Red Hat Enterprise Linux 8, executable Python scripts are expected to use hashbangs (shebangs) specifying explicitly at least the major Python version.

The /usr/lib/rpm/redhat/brp-mangle-shebangs buildroot policy (BRP) script is run automatically when building any RPM package, and attempts to correct hashbangs in all executable files.

#! /usr/bin/python

#! /usr/bin/env python

%undefine %brp_mangle_shebangs