#32103 closed Bug (invalid)
NotImplementedError in twisted (with Python 3.8 on Windows)
Reported by: | Andrey Zelenchuk | Owned by: | nobody |
---|---|---|---|
Component: | Core (Management commands) | Version: | 3.1 |
Severity: | Normal | Keywords: | |
Cc: | Triage Stage: | Unreviewed | |
Has patch: | no | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description
The runserver
management command does not work with Python ≥ 3.8 on Windows.
Steps to reproduce
- Open any Django project.
- Run
python manage.py runserver
.
Actual result
C:\Programs\Python38\python.exe C:/project/manage.py runserver 2020-10-11 18:12:08,823 INFO [django.utils.autoreload] Watching for file changes with StatReloader Exception in thread django-main-thread: Traceback (most recent call last): File "C:\Programs\Python38\lib\threading.py", line 932, in _bootstrap_inner self.run() File "C:\Programs\Python38\lib\threading.py", line 870, in run self._target(*self._args, **self._kwargs) File "C:\Programs\Python38\lib\site-packages\django\utils\autoreload.py", line 53, in wrapper fn(*args, **kwargs) File "C:\Programs\Python38\lib\site-packages\django\core\management\commands\runserver.py", line 110, in inner_run autoreload.raise_last_exception() File "C:\Programs\Python38\lib\site-packages\django\utils\autoreload.py", line 76, in raise_last_exception raise _exception[1] File "C:\Programs\Python38\lib\site-packages\django\core\management\__init__.py", line 357, in execute autoreload.check_errors(django.setup)() File "C:\Programs\Python38\lib\site-packages\django\utils\autoreload.py", line 53, in wrapper fn(*args, **kwargs) File "C:\Programs\Python38\lib\site-packages\django\__init__.py", line 24, in setup apps.populate(settings.INSTALLED_APPS) File "C:\Programs\Python38\lib\site-packages\django\apps\registry.py", line 91, in populate app_config = AppConfig.create(entry) File "C:\Programs\Python38\lib\site-packages\django\apps\config.py", line 116, in create mod = import_module(mod_path) File "C:\Programs\Python38\lib\importlib\__init__.py", line 127, in import_module return _bootstrap._gcd_import(name[level:], package, level) File "<frozen importlib._bootstrap>", line 1014, in _gcd_import File "<frozen importlib._bootstrap>", line 991, in _find_and_load File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked File "<frozen importlib._bootstrap>", line 671, in _load_unlocked File "<frozen importlib._bootstrap_external>", line 783, in exec_module File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed File "C:\Programs\Python38\lib\site-packages\channels\apps.py", line 6, in <module> import daphne.server File "C:\Programs\Python38\lib\site-packages\daphne\server.py", line 20, in <module> asyncioreactor.install(twisted_loop) File "C:\Programs\Python38\lib\site-packages\twisted\internet\asyncioreactor.py", line 320, in install reactor = AsyncioSelectorReactor(eventloop) File "C:\Programs\Python38\lib\site-packages\twisted\internet\asyncioreactor.py", line 69, in __init__ super().__init__() File "C:\Programs\Python38\lib\site-packages\twisted\internet\base.py", line 571, in __init__ self.installWaker() File "C:\Programs\Python38\lib\site-packages\twisted\internet\posixbase.py", line 286, in installWaker self.addReader(self.waker) File "C:\Programs\Python38\lib\site-packages\twisted\internet\asyncioreactor.py", line 151, in addReader self._asyncioEventloop.add_reader(fd, callWithLogger, reader, File "C:\Programs\Python38\lib\asyncio\events.py", line 501, in add_reader raise NotImplementedError NotImplementedError
Expected result
No errors.
Workaround
Add the following code to the manage.py
file:
if sys.platform == 'win32' and sys.version_info >= (3, 8): import asyncio asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
References
Change History (6)
comment:1 by , 4 years ago
Resolution: | → invalid |
---|---|
Severity: | Release blocker → Normal |
Status: | new → closed |
Summary: | runserver: NotImplementedError (with Python 3.8 on Windows) → NotImplementedError in twisted (with Python 3.8 on Windows) |
comment:2 by , 4 years ago
Windows on Python 3.8+ uses ProactorEventLoop, which is not compatible with
Twisted. Does not implement add_writer/add_reader.
See https://bugs.python.org/issue37373
and https://twistedmatrix.com/trac/ticket/9766
Recent versions of Daphne automatically set the correct event loop policy in these cases.
comment:3 by , 4 years ago
Windows on Python 3.8+ uses ProactorEventLoop
This is not accurate. Python 3.8+ on Windows uses the ProactorEventLoop by default. Python 3.8+ on Windows allows to use the SelectorEventLoop as well.
<...> which is not compatible with Twisted
So why then Django tries to use the ProactorEventLoop with Twisted?
Recent versions of Daphne automatically set the correct event loop policy in these cases.
Django's runserver
management command does not use Daphne, does it? Why Django cannot set the correct event loop policy too?
This ticket is not invalid until the Django's documentation states that Django does not support Python 3.8+ on Windows. Besides, it looks like it can be fixed quite easily. So, could you reopen it, please?
follow-up: 6 comment:4 by , 4 years ago
Your stack trace says you're using channels, which does use Daphne/twisted yes.
comment:5 by , 4 years ago
This ticket is not invalid until the Django's documentation states that Django does not support Python 3.8+ on Windows. Besides, it looks like it can be fixed quite easily. So, could you reopen it, please?
Django supports Python 3.8 on Windows, bugs in other packages that you can use with Django doesn't change this, we cannot add workarounds for bugs which are not in Django itself. Also (as mentioned by Carlton) it's already fixed in a pre-release version of twisted
.
comment:6 by , 4 years ago
Your stack trace says you're using channels, which does use Daphne/twisted yes.
Yes, that's right, thank you! Sorry, I missed that Channels replaces the Django's runserver
management command. This bug is invalid for Django, and it is already fixed in the recent version of Channels/Daphne/Twisted.
This is not an issue in Django but in
twisted
. Please report it in their bug tracker.