Port Mopidy to Python 3

[jodal]

Python 3 is the future of Python, it is widely available on the environments Mopidy is deployed on, and I'm quite interested in being able to use asyncio, which requires Python 3.3+. There's nothing outside the Mopidy project blocking us from moving to Python 3.

This is the master bug to track our way towards running Mopidy on Python 3.

• Dependencies:
  • Pykka supports Python 2.6+, 3.2+.
  • Tornado supports Python 2.6+, 3.2+.
  • GStreamer:
    • Switch to GStreamer 1.0 and PyGI #225: Switch GStreamer Python bindings from gst-python (Python 2 only) to PyGI (Python 2+3). To get everything working with PyGI, a port of GStreamer from 0.10 to 1.x at the same time is required.
    • Prepare for loosing gst mixers #665: Make mixers independent of GStreamer, as mixers are removed in GStreamer 1.x.
    • Consolidate playlist handling code #671: Extract/reimplement our playlist format support to not depend on GStreamer. There's some issues with reimplementing this on top of PyGI/GStreamer 1.x.
• Move code style towards being Python 2+3 compatible:
  • flake8 warning clean code.
  • Drop support for all Python versions older than 2.7.
  • Use from __future__ import unicode_literals everywhere and mark binary strings with b'foo'.
  • Selectively fix portability issues identified by the 2to3 tool.
• Development support:
  • Use tox to run tests, so we can easily add Python 3 testing in parallel with Python 2.7.
• Mopidy-Spotify:
  • Implement new libspotify binding, pyspotify 2, which supports Python 2.7, 3.2+.
  • Reimplement Mopidy-Spotify on top of pyspotify 2.
• Mopidy-MPRIS:
  • python-indicate bindings to libindicate can be replaced with PyGI.
  • python-dbus can maybe be replaced by GDBus through PyGI.
• Extension ecosystem:
  • Use tox as test runner in cookiecutter-mopidy-ext to be ready to start running tests on Python 3 too.
  • Send pull requests/create issues for Python 2+3 support in all extensions when Mopidy itself works on Python 2+3.
• Once ~all extensions supports Python 2+3, drop Python 2 support in Mopidy.
• Remove Python 2isms.
• Enjoy new Python 3 features, like asyncio.

[DanielFallon]

Hey, I'd like to help with Python 3 migration, anything in particular that's under way? don't want to step on anyone's toes

[jodal]

I've started a branch at jodal/feature/py3-compat where I've:

• updated the Python version check that stops you from starting Mopidy under Python 3
• updated the tox.ini setup
• starting fixing Py3 issues module-by-module, running the tests under both Python 2 and Python 3

I haven't touched this since November, except that I rebased the branch on top of Mopidy 2.0.0 a couple of days ago. The current status is that I've fixed around 1000 tests, with about 240 remaining.

The plan ahead is to:

1. Fix the rest of the issues module-by-module.
2. Take the experience from fixing all the issues and try to land as much of it as possible in Mopidy 2.x. My current module-by-module approach changes things (e.g. it starts to threat file paths as Unicode instead of bytes) that I don't want to land in Mopidy until the 3.0 release, where we're allowed to break things. The can't-land-until-3.0 diff should be as small as possible.
3. Use Mopidy with Python 3, finding all the issues not covered by tests.

[DanielFallon]

ok, I will fork off of that branch and try to fix whatever tests I can

[aleprovencio]

Hello guys, any news on this issue?

[flying-sheep]

3½ years left for this 😉

[Prior99]

Are there any updates on this?

[jodal]

Porting to Python 3 is my personal highest priority task when working on Mopidy, problem is I have been quite busy with work for the last year.

My current plan, in approximate order, is to:

• Fix the Mopidy-MPRIS test suite, so that it can survive the upcoming changes. This is a bit boring and my doorstep mile.
• Remove all the deprecated stuff from Mopidy and make a major release. See this milestone for the detailed issues. This I look forward to.
• Ensure that all extensions in the Mopidy org still works after the removal, and make necessary changes and releases.
• Port Mopidy to Python 2 + 3 and make another major release.
• Port all extensions in the Mopidy org to Python 3 only and release.
• Port/help port all other extensions to Python 3 only and urge for release.
• Remove the Python 2 support from Mopidy itself.

As you can see, there's a couple of tasks that should be done first before starting the porting itself. That said, the largest body of work is already complete: Rewriting pyspotify to workon Python 3 (two years of my spare time was spent here) and porting Mopidy to GStreamer 1.x (one paternity leave of spare time spent here).

I'll get there, but it takes time. If people want to help out, I think the most helpful would be helping port extensions to Python 3 as soon as Mopidy supports 2+3.

[Prior99]

Thanks for the update, @jodal.

[eamanu]

I Think that is a good idea move to Python3. I am new in mopidy and have never contributed to it, do you think that I can help you with something? El mié., 22 de mar. de 2017 a la(s) 07:08, Frederick Gnodtke < notifications@github.com> escribió:

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