FinalizingFedoraSwitchtoPython3

Finalizing Fedora's Switch to Python 3

Summary

Currently, in Fedora package names, python without a version number generally means Python 2. Given that the upstream support for Python 2 will eventually end, we want to to prepare Fedora for a transition to Python 3 as a default. Before switching python to refer to python3, a lot of preparatory work needs to be done and this page explains our plan to achieve this.

Owner

• Name: Iryna Shcherbina
• Email: ishcherb at redhat.com
• Name: Miro Hrončok
• Email: mhroncok at redhat.com
• Name: Petr Viktorin
• Email: pviktori at redhat.com

Current status

• Last updated: 2017-06-25

The current situation in Fedora ("correct" means "follows current packaging guidelines"):

• Correct package supporting Python 2 and 3 builds these binary RPMs:
  • python2-foo (provides python-foo as a virtual provide via %python_provides)
  • python3-foo (uses %python_provides, which is currently no-op)

• "Misnamed" package supporting py2/3 builds these binary RPMs:
  • python-foo (the py2 version; may provide python2-foo virtually, but usually doesn't)
  • python3-foo

• Correct py2-only packages are named:
  • python2-foo (provides python-foo as a virtual provide via %python_provides)

• Correct py3-only packages are named:
  • python3-foo (uses %python_provides, which is currently no-op)

• "Misnamed" py2-only package might be named:
  • python-foo, or
  • pyfoo, or
  • foo-python, etc.

• There are (close to) no "misnamed" py3-only packages

Detailed Description

TBD

Transition Steps

Phase 1: Eliminate the python- prefix from the Python 2 package names

• Targeted release: Fedora 30
• Description: Ensure that all python-foo names are solely virtual provides declarations, with the actual RPMs themselves being named python2-foo. python-foo names are also not to be used to declare the dependencies of a Python 2 package. This is a preparatory phase to clean up Fedora's Python packages and ensure consistency not only for new Python packages, but also for existing ones.
• Steps:
  • Identify the packages with naming issues. Those include packages with misnamed binary RPMs and dependencies.
  • Inform the package maintainers about the issues. Gather feedback and encoursge fixing the packages.
  • Start mass bug filing slowly: open e.g. 20 Bugzillas and learn from the reaction.

Phase 2: Switch python to refer to python3

• Targeted release: Fedora 32
• Description: Make Python 3 a default version of Python in Fedora. This would mean that installing a python-foo package will imply a Python 3 version on the package, and invoking python will run a Python 3 version on the interpreter. The steps needed to achive this will be done in combination with proposing changes to the upstream guidance in PEP 394.
• Steps:
  • Switch %python_provides macro to provide python-foo from python3-foo instead of python2-foo
  • Switch /usr/bin/python to point to /usr/bin/python3

Phase 3: Orphan python2 package

• Targeted release: Fedora 33
• Description: Python maintainers stop maintaining python2 package in Fedora. It will probably be picked up by someone from Python SIG.

Benefit to Fedora

This change simplifies transition to Python 3, when the upstream support for Python 2 ends.

Scope

• Proposal owners:

Feature owners have to communicate the idea to the packagers and provide all the detailed information. They may step in to fix the packages if absolutely needed.

• Other developers:

Package maintainers affected by the naming policies will be asked to fix their packages via mailing lists and Bugzilla.

• Policies and guidelines:
  • Using python2/python3 instead of python in binary RPM package name guidelines, fpc
  • Using python2/python3 instead of python in (Build)Requires guidelines, fpc

How To Test

TBD

Dependencies

Only those Python 2 packages which use python- prefix in dependency declarations are expected to break. However, when the change is completed, no packages like this are expected to exist.

Documentation

Discussion on Fedora devel mailing list

PEP 394