使用Python運行tornado項目時出現NotImplementedError錯誤怎么解決

使用Python運行tornado項目時出現NotImplementedError錯誤怎么解決？很多新手對此不是很清楚，為了幫助大家解決這個難題，下面小編將為大家詳細講解，有這方面需求的人可以來學習下，希望你能有所收獲。

今天拉了一個使用了tornado的項目在本地跑，按照源碼作者的步驟配置完，運行，直接報錯了，要求環境Python3.6+，我裝的是Python3.8，理論上應該直接正常運行的，報錯信息：

Traceback (most recent call last):
  File "ice_server.py", line 150, in <module>
    RunServer.run_server(port=p, host=h)
  File "ice_server.py", line 125, in run_server
    tornado_server.start()
  File "D:\PycharmProjects\ice\venv\lib\site-packages\tornado\tcpserver.py", line 244, in start
    self.add_sockets(sockets)
  File "D:\PycharmProjects\ice\venv\lib\site-packages\tornado\tcpserver.py", line 165, in add_sockets
    self._handlers[sock.fileno()] = add_accept_handler(
  File "D:\PycharmProjects\ice\venv\lib\site-packages\tornado\netutil.py", line 279, in add_accept_handler
    io_loop.add_handler(sock, accept_handler, IOLoop.READ)
  File "D:\PycharmProjects\ice\venv\lib\site-packages\tornado\platform\asyncio.py", line 100, in add_handler
    self.asyncio_loop.add_reader(fd, self._handle_events, fd, IOLoop.READ)
  File "C:\Users\huan\AppData\Local\Programs\Python\Python38\lib\asyncio\events.py", line 501, in add_reader
    raise NotImplementedError
NotImplementedError

一番谷歌原來對于這個問題tornado的參與者們已經收到了很多反饋，有個回復里這么說：

Python 3.8 asyncio is going to make the "proactor" event loop the default, instead of the current "selector" event loop. This is a problem for Tornado because the proactor event loop doesn't support the unix-style add_reader APIs that Tornado uses.

Anyone using Tornado 5+ on windows with python 3.8 will need to configure asyncio to use the selector event loop; we'll have to document this. We should also try to detect the use of a proactor event loop and give a clear error message

大概意思Python3.8的asyncio改變了循環方式，因為這種方式在windows上不支持相應的add_reader APIs，就會拋出NotImplementedError錯誤。

解決辦法

找到這個項目使用的python環境的lib\site-packages，做下面的修改，在path-to-python\lib\site-packages\tornado\platform\asyncio.py開頭添加代碼：

import sys

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

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