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。

巴特西

asyncio标准库1 Hello World

Simple coroutine（调用1个协程）

Creating tasks（调用多个协程）

Stopping the loop

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