asyncio标准库1 Hello World
利用asyncio的event loop，编写和调度协程 coroutine [,kəuru:'ti:n] n. 协程
Simple coroutine（调用1个协程）
import asyncio
async def say(what, when):
await asyncio.sleep(when)
print(what)
loop = asyncio.get_event_loop()
loop.run_until_complete(say('hello world', 1)) # 使用run_until_complete()方法，在协程完成后中断event loop。
loop.close()
Creating tasks（调用多个协程）
import asyncio
async def say(what, when):
await asyncio.sleep(when)
print(what)
loop = asyncio.get_event_loop()
loop.create_task(say('first hello', 2))
loop.create_task(say('second hello', 1))
loop.run_forever() # 使用run_forever()方法，协程会一直运行，不会中断event loop
loop.close()
Stopping the loop
import asyncio
async def say(what, when):
await asyncio.sleep(when)
print(what)
async def stop_after(loop, when):
await asyncio.sleep(when)
loop.stop() # 中断event loop
loop = asyncio.get_event_loop()
loop.create_task(say('first hello', 2))
loop.create_task(say('second hello', 1))
loop.create_task(say('third hello', 4))
loop.create_task(stop_after(loop, 3))
loop.run_forever()
loop.close()
# out:
second hello
first hello
Task was destroyed but it is pending!
task: <Task pending coro=<say() done, defined at e03.py:5> wait_for=<Future pending cb=[<TaskWakeupMethWrapper object at 0x7fed59595a68>()]>>
# 在执行2个任务后，中断event loop，'third hello‘任务由于延迟时间4秒，未能执行。
posted on
2018-03-19 10:55
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转载于:https://www.cnblogs.com/liujitao79/p/8600660.html
