Python asyncio中奇怪的断言错误
我正试图用以下代码通过超时标记将来完成:Python asyncio中奇怪的断言错误,python,python-3.x,python-asyncio,Python,Python 3.x,Python Asyncio,我正试图用以下代码通过超时标记将来完成: import asyncio @asyncio.coroutine def greet(): while True: print('Hello World') yield from asyncio.sleep(1) @asyncio.coroutine def main(): future = asyncio.async(greet()) loop.call_later(3, lambda:
import asyncio
@asyncio.coroutine
def greet():
while True:
print('Hello World')
yield from asyncio.sleep(1)
@asyncio.coroutine
def main():
future = asyncio.async(greet())
loop.call_later(3, lambda: future.set_result(True))
yield from future
print('Ready')
loop = asyncio.get_event_loop()
loop.run_until_complete(main())
“Timer”loop.call_稍后会在3秒后将结果设置为future。这是可行的,但我也有例外:
Hello World
Hello World
Hello World
Ready
Exception in callback <bound method Task._wakeup of Task(<greet>)<result=True>>(Future<result=None>,)
handle: Handle(<bound method Task._wakeup of Task(<greet>)<result=True>>, (Future<result=None>,))
Traceback (most recent call last):
File "C:\Python33\lib\site-packages\asyncio\events.py", line 39, in _run
self._callback(*self._args)
File "C:\Python33\lib\site-packages\asyncio\tasks.py", line 337, in _wakeup
self._step(value, None)
File "C:\Python33\lib\site-packages\asyncio\tasks.py", line 267, in _step
'_step(): already done: {!r}, {!r}, {!r}'.format(self, value, exc)
AssertionError: _step(): already done: Task(<greet>)<result=True>, None, None
你好,世界
你好,世界
你好,世界
准备好的
回调中的异常(将来,)
句柄:句柄(,(未来,))
回溯(最近一次呼叫最后一次):
文件“C:\Python33\lib\site packages\asyncio\events.py”,第39行,正在运行
self.\u回调(*self.\u参数)
文件“C:\Python33\lib\site packages\asyncio\tasks.py”,第337行,在_wakeup中
自身步骤(值,无)
文件“C:\Python33\lib\site packages\asyncio\tasks.py”,第267行,步骤
“_step():已完成:{!r},{!r},{!r}”。格式(self,value,exc)
断言错误:_步骤():已完成:任务(),无,无
这个断言错误是什么意思?我是否在通过循环设置future done by loop时出错。请稍后调用?导致异常的原因:
greet
即使在future之后仍会继续运行。set_result
调用;通过使用if True
更改while True
,您将了解我的意思
使用如何
你不应该自己调用
future.set\u result()
。事件循环设置任务返回后的未来结果
import asyncio
@asyncio.coroutine
def greet(stop):
while not stop.is_set():
print('Hello World')
yield from asyncio.sleep(1)
@asyncio.coroutine
def main():
stop = asyncio.Event()
loop.call_later(3, stop.set)
yield from asyncio.async(greet(stop))
print('Ready')
loop = asyncio.get_event_loop()
loop.run_until_complete(main())