Question

在从asyncio.get_event_loop（）获取的循环上调用loop.close（）之后的Python3.6.1中，是否可以创建一个新循环？

我已经查看了其他帖子，其中包含正确关闭循环的答案，以及如何使用task.cancel（），但未能以某种方式使用任何这些示例在第一次关闭后创建循环。我也尝试显式设置执行程序，然后调用executor.shutdown（wait = True），但这没有用。我也尝试过“循环”和其他一些东西。

文档表明关闭一个事件循环是幂等的，不可逆转的。这是否意味着无法创建新循环？

以下是一些用于演示此问题的简单示例代码： `

#!/usr/bin/env python3.6
'''
To demonstrate an issue, the following code was adapted from:
https://docs.python.org/3/library/asyncio-eventloop.html
'''
import asyncio

def hello_world(loop):
    print('Hello World')
    loop.stop()

loop = asyncio.get_event_loop()
loop.call_soon(hello_world, loop)
loop.run_forever()
# loop.close()


'''
If the commented out loop.close() above is uncommented,
the following code will fail with:
    Traceback (most recent call last):
        File "./aquestion.py", line 28, in <module>
            loopNew.call_soon(hello_world, loopNew)
        File "/Library/Frameworks/Python.framework/Versions/3.6/lib    /python3.6/asyncio/base_events.py", line 573, in call_soon
        self._check_closed()
        File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncio/base_events.py", line 357, in _check_closed
            raise RuntimeError('Event loop is closed')
    RuntimeError: Event loop is closed

'''
loopNew = asyncio.get_event_loop()
loopNew.call_soon(hello_world, loopNew)
loopNew.run_forever()

#!/usr/bin/env python3.6
'''
To demonstrate an issue, the following code was adapted from:
https://docs.python.org/3/library/asyncio-eventloop.html
'''
import asyncio

def hello_world(loop):
    print('Hello World')
    loop.stop()

loop = asyncio.get_event_loop()
loop.call_soon(hello_world, loop)
loop.run_forever()
# loop.close()


'''
If the commented out loop.close() above is uncommented,
the following code will fail with:
    Traceback (most recent call last):
        File "./aquestion.py", line 28, in <module>
            loopNew.call_soon(hello_world, loopNew)
        File "/Library/Frameworks/Python.framework/Versions/3.6/lib    /python3.6/asyncio/base_events.py", line 573, in call_soon
        self._check_closed()
        File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncio/base_events.py", line 357, in _check_closed
            raise RuntimeError('Event loop is closed')
    RuntimeError: Event loop is closed

'''
loopNew = asyncio.get_event_loop()
loopNew.call_soon(hello_world, loopNew)
loopNew.run_forever()

`

任何回答我的问题的尝试都将不胜感激。

或者，创建一个事件循环，将它用于各种目的，然后在长时间运行的程序即将退出时关闭该循环是不好的形式？这似乎是错的。

Answer 1

asyncio.get_event_loop返回当前循环。它不关注循环的状态。如果在关闭之后需要新循环，则可以使用asyncio.new_event_loop。

请注意，获取新循环不会影响对get_event_loop的后续调用。如果您希望返回新的循环而非原始循环（特别是因为您可能已关闭它），您需要自己致电asyncio.set_event_loop。

import asyncio

async def f():
    await asyncio.sleep(0)

loop = asyncio.get_event_loop()
loop.run_until_complete(f())
loop.close()

loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)

在Python3.6.1中调用loop.close asyncio.get_event_loop后无法创建新的事件循环

1 个答案: