在我的 async
处理程序中,我想等到任务的状态发生变化。现在,我只是在无限循环中检查状态并等待。这是一个示例,wait_until_done
函数:
import asyncio
class LongTask:
state = 'PENDING'
my_task = LongTask()
def done():
my_task.state = 'DONE'
async def wait_until_done():
while True:
if my_task.state == 'PENDING':
await asyncio.sleep(2)
else:
break
print("Finally, the task is done")
def main(loop, *args, **kwargs):
asyncio.ensure_future(wait_until_done())
loop.call_later(delay=5, callback=done)
loop = asyncio.get_event_loop()
main(loop)
loop.run_forever()
有更好的方法吗?
最佳答案
为了避免混淆:我猜你不是在谈论 asyncio.Task ,而是一些变量状态,对吧?
在这种情况下,您有 Future和 synchronization primitives这使您可以等待异步更改的某些内容。
如果需要在两种状态之间切换,asyncio.Event可能是你想要的。这是一个小例子:
import asyncio
my_task = asyncio.Event()
def done():
my_task.set()
async def wait_until_done():
await my_task.wait() # await until event would be .set()
print("Finally, the task is done")
async def main():
loop.call_later(delay=5, callback=done)
await wait_until_done()
loop = asyncio.get_event_loop()
try:
loop.run_until_complete(main())
finally:
loop.run_until_complete(loop.shutdown_asyncgens())
loop.close()
更新:
保持 LongTask
接口(interface)的更复杂的例子:
import asyncio
class LongTask:
_event = asyncio.Event()
@property
def state(self):
return 'PENDING' if not type(self)._event.is_set() else 'DONE'
@state.setter
def state(self, val):
if val == 'PENDING':
type(self)._event.clear()
elif val == 'DONE':
type(self)._event.set()
else:
raise ValueError('Bad state value.')
async def is_done(self):
return (await type(self)._event.wait())
my_task = LongTask()
def done():
my_task.state = 'DONE'
async def wait_until_done():
await my_task.is_done()
print("Finally, the task is done")
async def main():
loop.call_later(delay=5, callback=done)
await wait_until_done()
loop = asyncio.get_event_loop()
try:
loop.run_until_complete(main())
finally:
loop.run_until_complete(loop.shutdown_asyncgens())
loop.close()
关于python - 如何等待对象改变状态,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/44891761/