Changes/Python3.7

Python 3.7

Summary

Update the Python 3 stack in Fedora from Python 3.6 to Python 3.7.

Owner

• Name: Charalampos Stratakis
• Name: Miro Hrončok
• Name: Tomáš Orsava
• Name: Petr Viktorin

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

Current status

• Targeted release: Fedora 29
• Last updated: 2018-07-02
• Tracker bug: #1565020
• Release Notes tracking: #133

Detailed Description

Python 3.7 adds numerous features and optimizations. See the upstream notes at Features for 3.7 and What's new in 3.7.

Important dates

• 2018-06-11 Python 3.7.0 candidate 1
• 2018-06-27 Python 3.7.0 final
• 2018-07-11 Fedora 29 Mass Rebuild
• 2018-08-14 Fedora 29 Change Checkpoint: Completion deadline (testable)

(From Python 3.7 Release Schedule and Fedora 29 Release Schedule.)

PEP 552 – Deterministic pycs

One change is notable from the packaging viewpoint: PEP 552 – “Deterministic pycs”. We may decide to use the new UNCHECKED_HASH mode, which would mean that bytecode cache is not validated on import, i.e. changing a RPM-installed *.py file manually will have no effect (unless the corresponding __pycache__/*.pyc is updated or removed). We haven't decided for this.

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 3.7.

Scope

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

• Proposal owners:
  1. Retire python37 from F29+
  2. Update python3 to what was in python37
     • Mass rebuild all the packages that BR python3/python3-devel/... (~2300 listed in Python 3 Porting Database for Fedora)
  3. Reintroduce python36 from Fedora 25. Update it to have all fixes and enhancements from python3 in Fedora 28 (or 29 before this change)

• Other developers: Maintainers of packages that fail to rebuild during the mass rebuild 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 upstreams first and/or applying downstream patches. Also the package maintainers should have a look at: Porting to Python 3.7. 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.

• Release engineering: #7390 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 3.6 is forward compatible with Python 3.7.

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 3.7 and verify that it still works as you expect. You can test it using python37 even before this change is implemented, in Fedora 27 or 28.

Once the change is in place, test if you favorite Python apps are working as they were before. File bugzillas 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 3.7.

Dependencies

~2300 packages depends 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 3.6 version (never needed before)
• Contingency deadline: TBD
• Blocks release? No
• Blocks product? No

Documentation

Python 3.7 Release Schedule

Features for 3.7

What's new in 3.7

Porting to Python 3.7

Release Notes

• Release Notes tracking: #133