这是简单的测试代码和结果.
import asyncio
async def test():
await asyncio.sleep(1)
if __name__ == '__main__':
asyncio.set_event_loop(None) # Clear the main loop.
loop = asyncio.new_event_loop() # Create a new loop.
loop.run_until_complete(test()) # Run coroutine over the new loop
Traceback (most recent call last):
File "test_test.py", line 11, in
loop.run_until_complete(test())
File "/usr/lib/python3.5/asyncio/base_events.py", line 387, in run_until_complete
return future.result()
File "/usr/lib/python3.5/asyncio/futures.py", line 274, in result
raise self._exception
File "/usr/lib/python3.5/asyncio/tasks.py", line 239, in _step
result = coro.send(None)
File "test_test.py", line 5, in test
await asyncio.sleep(1)
File "/usr/lib/python3.5/asyncio/tasks.py", line 510, in sleep
loop = events.get_event_loop()
File "/usr/lib/python3.5/asyncio/events.py", line 632, in get_event_loop
return get_event_loop_policy().get_event_loop()
File "/usr/lib/python3.5/asyncio/events.py", line 578, in get_event_loop
% threading.current_thread().name)
RuntimeError: There is no current event loop in thread 'MainThread'.
我在新循环上运行异步def测试(),并期望由test()嵌套的asyncio.sleep(1)也使用新循环.
与此相反,sleep()似乎仍然可以访问我设置为None的主循环.
我知道在调用run_until_complete()之前我可以使用asyncio.set_event_loop(循环)将主循环重新设置为新循环,并且它将无异常地工作.
但是,我想知道asyncio是正常的,主循环必须设置并用于协同程序,而不管运行协同程序的循环.
解决方法:
I want to know it is normal for asyncio that main loop Must be set and is used for coroutines regardless of a loop over which coroutine is run.
过去在Python 3.6之前需要这样做.原因是像asyncio.sleep()这样的函数需要一个事件循环才能使用loop.call_later()来安排唤醒调用以完成未来.
从Python 3.6(或3.5.3,包括the issue的修复)开始,当从事件循环驱动的协同程序调用get_event_loop()时,它总是返回驱动它的事件循环.因此,您的代码可以正常工作.
An exception to this rule happens when get_event_loop() is called from a running future/coroutine, in which case it will return the current loop running that future/coroutine.
标签：python,python-3-x,python-asyncio,python-3-5,event-loop