Changes/Python3.8

Python 3.8

Summary

Update the Python stack in Fedora from Python 3.7 to Python 3.8.

Owner

• Name: Miro Hrončok

• Email: python-maint@redhat.com
• Release notes owner:

Current status

• Targeted release: Fedora 31
• Last updated: 2019-06-18
• Tracker bug: #1686977
• Release notes tracker: #310

Detailed Description

We would like to upgrade Python to 3.8 in Fedora 31 thus we are proposing this plan early.

See the upstream notes at Features for 3.8 and What's new in 3.8.

Important dates and plan

• 2019-02-03 Python 3.8.0 alpha 1
  • Package it as python38 for testing purposes
  • Start the bootstrap procedure in Copr
  • Do a mass rebuild against every future release in Copr
• 2019-05-31 Python 3.8.0 beta 1 (was: 2019-05-27)
  • If the Copr mass rebuild results were good, we will push the update to rawhide and do the bootstrapping + mass rebuild in a side tag
• , 2019-06-24 Python 3.8.0 beta 2
  • If the side tag bootstrapping and mass rebuild results were good, we will merge it to Fedora at this point
• 2019-07-24 expected earliest Fedora 31 mass rebuild
• 2019-08-29 expected earliest Fedora 31 beta freeze
  • Everything should be well tested on beta 1 to 4
• 2019-09-30 Python 3.8.0 candidate 1
  • (we block Fedora release before we have this)
• 2019-10-08 expected earliest Fedora 31 final freeze
• 2019-10-21 Python 3.8.0 final
  • Gets in with a pre-approved exception
• 2019-10-22 Fedora Final Release (GA) (Preferred Target)
• 2019-10-29 Fedora Final Release (GA) (Target #1)

(From Python 3.8 Release Schedule and Fedora 31 Release Schedule.)

The schedule is very tight, but the Fedora dates are the earliest estimates. So we are proposing this early, in the case the Fedora schedule might need to be adjusted.

Note that upstream's "release candidates" are frozen except for blocker bugs. Since we can and will backport blocker fixes between Fedora and upstream, we essentially treat the Release Candidate as the final release.

Notes from the previous upgrade

There are notes from the previous upgrade available, so this upgrade may go smoother: SIGs/Python/UpgradingPython

Benefit to Fedora

Fedora aims to showcase the latest in free and open source software - we should have the most recent release of Python 3. Packages in Fedora can use the new features from 3.8.

There's also a benefit to the larger Python ecosystem: by building Fedora's packages against 3.8 while it's still in development, we can catch critical bugs before the final 3.8.0 release.

Scope

We will coordinate the work in a side tag and merge when ready.

• Proposal owners:
  1. Introduce python38 for all Fedoras
  2. Prepare stuff in Copr as explained in description.
  3. Retire python38 from F31+
  4. Update python3 to what was in python38
     • Mass rebuild all the packages that BR python3/python3-devel/... (~2700 listed in Python 3 Porting Database for Fedora)
  5. Reintroduce python37 from Fedora 28. Update it to have all fixes and enhancements from python3 in Fedora 30 (or 31 before this change)

• Other developers: Maintainers of packages that fail to rebuild during the rebuilds will be asked, using e-mail and bugzilla, to fix or remove their packages from the distribution. If any issues appear, they should be solvable either by communicating with the respective upstreams first and/or applying downstream patches. Also the package maintainers should have a look at: Porting to Python 3.8. And python-maint team will be available to help with fixing issues.

• Fedora QA: Based on some troubles with the change to 3.6, we'd like to have an ack from QA before we merge the side tag. We'd also like QA to approve this change.

• Release engineering: #8092 A targeted rebuild for all python packages will be required, before the mass rebuild.
  • List of deliverables: nope

• Policies and guidelines: nope

• Trademark approval: nope

Upgrade/compatibility impact

All the packages that depend on Python 3 must be rebuilt. User written Python 3 scripts/applications may require a small amount of porting, but mostly Python 3.7 is forward compatible with Python 3.8.

How To Test

Interested testers do not need special hardware. If you have a favorite Python 3 script, module, or application, please test it with Python 3.8 and verify that it still works as you would expect. If the application you are testing does not require any other modules, you can test it using python38 even before this change is implemented, in Fedora 29 or 30.

In case your application requires other modules, or if you are testing an rpm package, it is necessary to install the 3.8 version of the python3 rpm. Right now that rpm is available in copr, along with all other python packages that build successfully with python 3.8. See https://copr.fedorainfracloud.org/coprs/g/python/python3.8/ for detailed instructions how to enable copr for local use and how to enable it for mock.

Once the change is in place, test if you favorite Python apps are working as they were before. File bugs if they don't.

User Experience

Regular distro users shouldn't notice any change in system behavior other than the Python 3 interpreter will be in version 3.8.

Dependencies

~2700 packages depend on python3. See scope section.

Contingency Plan

• Contingency mechanism: Do not merge the side tag with rawhide. If the side tag has been merged and issues arise, that will justify a downgrade, then use an epoch tag to revert to 3.7 version (never needed before)
• Contingency deadline: TBD
• Blocks release? Yes, we'd like to block Fedora 31 release on at least 3.8.0 rc 1
• Blocks product? See above

Documentation

Python 3.8 Release Schedule

Features for 3.8

What's new in 3.8

Porting to Python 3.8

Release Notes

• Release Notes tracking: #XXX