ValueError: set_wakeup_fd only works in main thread on Windows on Python 3.8 with Django 3.0.2 or Flask 2.0.0
I have exactly the same bug. I opened the issue.
If you want to stay on the current Python version I have found the temporal solution which is to add following lines to asgiref\__init__.py (as it was suggested in issue):
if sys.platform == "win32" and sys.version_info >= (3, 8, 0): asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
Not only Django, but you will also meet this error with Flask since Flask 2.0.0 uses asgiref to support async.
This bug was fixed in Python 3.9, so there are two solutions:
- Upgrade to Python 3.9
- Add the temp fix as follows (based on Dennis B's answer) to your entry script, for example, Flask's
app.pyor Django'smanager.py:
# top of the fileimport sys, asyncioif sys.platform == "win32" and (3, 8, 0) <= sys.version_info < (3, 9, 0): asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
I had to downgrade to Python 3.7 and then it started to work perfectly.