Add support for Python 3.13

[llucax]

No description provided.

[llucax]

Sadly the new time-machine has issues with async-solipsism, as it also mocks the monotonic clock. We first need to get this sorted out before being able to merge this:

• Test freezes in CI after upgrade to v2.13.0 from v2.12.0 adamchainz/time-machine#387

time-machine 2.12 doesn't support Python 3.13.

[Copilot]

Pull Request Overview

This PR adds support for Python 3.13 across the project by updating documentation and CI configuration.

• Updated RELEASE_NOTES.md to announce Python 3.13 support
• Updated README.md to list Python 3.13 as a supported version
• Updated CI workflows to include Python 3.13 in the testing matrix

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
RELEASE_NOTES.md	Updated text announcing Python 3.13 support
README.md	Updated supported Python versions list
.github/workflows/ci.yaml	Added Python 3.13 to the CI testing configuration

[llucax]

Ready for review, thanks @shsms for #1221! 🎉

[llucax]

@shsms the CI says no (in the queue)

[llucax]

OK, this is a new one... It is failing for all 3.13 runs except arm, ci_checks_max (this one passes), and not really failing:

2025-05-17T06:01:06.3319377Z ================== 424 passed, 9 warnings in 93.42s (0:01:33) ==================

And it seems that after the tests are done, it gets stuck in some infinite loop. I'm attaching an extract of the logs because the logs are so big, it would be easier for other people to look at the extract.

• log-extract.txt

The repeated log is:

2025-05-17T06:01:49.5822344Z Actor PowerManagingActor[140302124270608]: Raised an unhandled exception.
2025-05-17T06:01:49.5823182Z Traceback (most recent call last):
2025-05-17T06:01:49.5824189Z   File "/home/runner/work/frequenz-sdk-python/frequenz-sdk-python/src/frequenz/sdk/actor/_actor.py", line 90, in _run_loop
2025-05-17T06:01:49.5825214Z     await self._delay_if_restart(n_restarts)
2025-05-17T06:01:49.5826325Z   File "/home/runner/work/frequenz-sdk-python/frequenz-sdk-python/src/frequenz/sdk/actor/_actor.py", line 73, in _delay_if_restart
2025-05-17T06:01:49.5827531Z     await asyncio.sleep(delay)
2025-05-17T06:01:49.5828384Z   File "/opt/hostedtoolcache/Python/3.13.3/x64/lib/python3.13/asyncio/tasks.py", line 712, in sleep
2025-05-17T06:01:49.5829201Z     loop = events.get_running_loop()
2025-05-17T06:01:49.5829648Z RuntimeError: no running event loop

I wonder if maybe we are trying to do some cleanup in some __del__ and Python3.13 retries it if it fails or something, but that doesn't explain why it works with one Python3.13. Since this involved the power manager, and you are very keen on getting Python3.13, maybe @shsms you can have a look? Otherwise I will when I have some time.

[shsms]

Interesting, I'm able to reproduce it locally, but only with pytest_max. I'll see if I can figure it out.

[shsms]

I wonder if this is a new python bug. It is running the async Actor._run_loop method infinitely. If the event loop is closed, that function should stop running as well, but it keeps running and tries to call await sleep and that's failing with RuntimeError: no running event loop, but the _run_loop function is not going away.

Longterm solution is to implement reference counting for shared actor lifetimes. But for now, we could do one of:

1. don't restart actor if no loop (this works):

diff --git a/src/frequenz/sdk/actor/_actor.py b/src/frequenz/sdk/actor/_actor.py
index e62c2b63..26b994ea 100644
--- a/src/frequenz/sdk/actor/_actor.py
+++ b/src/frequenz/sdk/actor/_actor.py
@@ -94,6 +94,9 @@ class Actor(BackgroundService, abc.ABC):
                 _logger.info("Actor %s: Cancelled.", self)
                 raise
             except Exception:  # pylint: disable=broad-except
+                if not asyncio.get_running_loop().is_running():
+                    _logger.info("Actor %s: Loop is closed, stopping...", self)
+                    raise
                 _logger.exception("Actor %s: Raised an unhandled exception.", self)
                 limit_str = "∞" if self._restart_limit is None else self._restart_limit
                 limit_str = f"({n_restarts}/{limit_str})"

2. Catch RuntimeError in actor.py, check description and raise if no loop. Haven't tried this, but should work.

[llucax]

If the dependency versions affect the results, I guess it is not purely a Python bug, or is a bug that only manifests in some dependency. Have you tried to pin-point which dependency upgrade triggers the bug? It might be useful to understand better what's going on and/or to pick one of the solutions.

My bets go to pytest or pytest-async (maybe solipsism if it is involved too), as it looks like our loop is closed, but there might be a second one still running and executing this code, otherwise I can't see how some async code could be executed after the loop is closed.

[llucax]

In particular if this is a regression on some test library, it might be more likely that it gets fixed soon.

[shsms]

Have you tried to pin-point which dependency upgrade triggers the bug?

No

My bets go to pytest or pytest-async (maybe solipsism if it is involved too),

Those are all pinned to a single version, under dev-pytest, can't imagine those don't explain the discrepancy between pytest_min/_max.

as it looks like our loop is closed, but there might be a second one still running and executing this code,

There is a function Actor._run_loop running in some event loop. That function is calling await sleep, and that is going to get created in the same loop as _run_loop, and that's failing. I don't think that's because of two different loops.

otherwise I can't see how some async code could be executed after the loop is closed.

I can 🤯 they have a 🐞

[shsms]

Actually you might be right, I'm thinking it must be a 🪲 in solipsism's event loop, because it is failing only with the TestEVChargerPoolControl tests as far as I can see and that uses async_solipsism, and the retries happen immediately after each other, without the 2-sec wait period that a regular actor would take.

But we use the same version of async-solipsism for min and max tests 🤔

I'll try some different versions.

[llucax]

Maybe it is an interaction between solipsism and py3.13, maybe solipsism is assuming some python internals that changed...

[shsms]

Actually it was just some missing cleanup. Fixed here: #1222

[llucax]

Awesome, but do you know how that explain async code being running outside the loop?

[shsms]

Awesome, but do you know how that explain async code being running outside the loop?

No, and I don't think it was solipsism. I disabled the solipsism event loop and it was still getting stuck. Maybe something to do with the MockMicrogrid, don't know. But I still feel it is Python.

[llucax]

You got the Python's vibe... 😆

OK, let's hope it doesn't come back to bite us...

[llucax]

Rebased, we can try again with the queue, but it needs a new approval @shsms

[llucax]

Awesome, thanks @shsms !