Python3.8 异步 asyncio

代码

import asyncio
import time


async def first_fun(delay):
    print('开始执行 first_fun 函数。')
    await asyncio.sleep(delay)
    print('first_fun 函数执行结束。')
    return delay


async def second_fun(delay):
    print('开始执行 second_fun 函数。')
    await asyncio.sleep(delay)
    print('second_fun 函数执行结束。')
    return delay


async def main():
    print(f"started at {time.strftime('%X')}")

    first = asyncio.create_task(first_fun(5))
    print('=============')
    second = asyncio.create_task(second_fun(4))
    # await first
    # await second
    print('=============')
    print(f"finished at {time.strftime('%X')}")


asyncio.run(main())

　　执行结果

started at 13:35:37
=============
=============
finished at 13:35:37
开始执行 first_fun 函数。
开始执行 second_fun 函数。

代码2

import asyncio
import time


async def first_fun(delay):
    print('开始执行 first_fun 函数。')
    await asyncio.sleep(delay)
    print('first_fun 函数执行结束。')
    return delay


async def second_fun(delay):
    print('开始执行 second_fun 函数。')
    await asyncio.sleep(delay)
    print('second_fun 函数执行结束。')
    return delay


async def main():
    print(f"started at {time.strftime('%X')}")

    first = asyncio.create_task(first_fun(5))
    print('=============')
    second = asyncio.create_task(second_fun(4))
    await first
    await second
    print('=============')
    print(f"finished at {time.strftime('%X')}")


asyncio.run(main())

　　执行结果

started at 13:37:20
=============
开始执行 first_fun 函数。
开始执行 second_fun 函数。
second_fun 函数执行结束。
first_fun 函数执行结束。
=============
finished at 13:37:25

结论

asyncio.create_task()：就相当于开启了一个线程。
await ：相当用线程的 join，等待协程的运行结束，再继续运行之后的代码。