I keep getting NotImplementedError error when starting django server

问题

Below is a full trace of the error. Please let me know what could fix this issue:

(env) C:\Users\LENOVO\Desktop\SD\backend>python manage.py runserver
    Watching for file changes with StatReloader
    Exception in thread django-main-thread:
    Traceback (most recent call last):
      File "C:\Users\LENOVO\AppData\Local\Programs\Python\Python38-32\lib\threading.py", line 932, in _bootstrap_inner
        self.run()
      File "C:\Users\LENOVO\AppData\Local\Programs\Python\Python38-32\lib\threading.py", line 870, in run
        self._target(*self._args, **self._kwargs)
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\django\utils\autoreload.py", line 54, in wrapper
        fn(*args, **kwargs)
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\django\core\management\commands\runserver.py", line 109, in inner_run
        autoreload.raise_last_exception()
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\django\utils\autoreload.py", line 77, in raise_last_exception
        raise _exception[1]
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\django\core\management\__init__.py", line 337, in execute
        autoreload.check_errors(django.setup)()
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\django\utils\autoreload.py", line 54, in wrapper
        fn(*args, **kwargs)


      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\django\__init__.py", line 24, in setup
        apps.populate(settings.INSTALLED_APPS)
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\django\apps\registry.py", line 91, in populate
        app_config = AppConfig.create(entry)
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\django\apps\config.py", line 116, in create
        mod = import_module(mod_path)
      File "C:\Users\LENOVO\AppData\Local\Programs\Python\Python38-32\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:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\channels\apps.py", line 6, in <module>
        import daphne.server
File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\daphne\server.py", line 18, in <module>
        asyncioreactor.install()
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\twisted\internet\asyncioreactor.py", line 320, in install
        reactor = AsyncioSelectorReactor(eventloop)
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\twisted\internet\asyncioreactor.py", line 69, in __init__
        super().__init__()
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\twisted\internet\base.py", line 571, in __init__
        self.installWaker()
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\twisted\internet\posixbase.py", line 286, in installWaker
        self.addReader(self.waker)
      File "C:\Users\LENOVO\Desktop\SD\backend\env\lib\site-packages\twisted\internet\asyncioreactor.py", line 151, in addReader
        self._asyncioEventloop.add_reader(fd, callWithLogger, reader,
      File "C:\Users\LENOVO\AppData\Local\Programs\Python\Python38-32\lib\asyncio\events.py", line 501, in add_reader
        raise NotImplementedError
    NotImplementedError

回答1:

Twisted is not supported on 3.8 on Windows, so one solution would be to switch back to Python 3.7.

I got it working on Python 3.8 by replacing the following lines in packages/twisted/internet/asyncioreactor.py

from twisted.internet.interfaces import IReactorFDSet

try:
    from asyncio import get_event_loop
except ImportError:
    raise ImportError("Requires asyncio.")

# As per ImportError above, this module is never imported on python 2, but

with

from twisted.internet.interfaces import IReactorFDSet

import sys

try:
    from asyncio import get_event_loop, set_event_loop_policy, WindowsSelectorEventLoopPolicy
except ImportError:
    raise ImportError("Requires asyncio.")

if sys.platform == 'win32':
    set_event_loop_policy(WindowsSelectorEventLoopPolicy())

# As per ImportError above, this module is never imported on python 2, but

From the similar problem faced by Tornado here.

来源：https://stackoverflow.com/questions/58908293/i-keep-getting-notimplementederror-error-when-starting-django-server