python async await 用洗衣服的场景来说明白

import time
import asyncio


def demo1():
    """普通版本 阻塞 需要9秒钟执行完毕"""
    def wash1():
        time.sleep(3)
        print("wash1 finished")

    def wash2():
        time.sleep(3)
        print("wash2 finished")

    def wash3():
        time.sleep(3)
        print("wash3 finished")

    wash1()
    wash2()
    wash3()


def demo2():
    """添加async关键字 创建协程 但是这个版本会报错：RuntimeWarning: Enable tracemalloc to get the object allocation traceback"""

    async def wash1():
        time.sleep(3)
        print("wash1 finished")

    async def wash2():
        time.sleep(3)
        print("wash2 finished")

    async def wash3():
        time.sleep(3)
        print("wash3 finished")

    wash1()
    wash2()
    wash3()


def demo3():
    """用async 和 await创建正确的协程  这个只需要3秒钟左右！"""
    async def wash1():
        await asyncio.sleep(3)  # 返回来一个可等待的对象， await后面必须跟一个awaitable类型或者具有 __await__属性的对象！
        print("wash1 finished")

    async def wash2():
        await asyncio.sleep(3)
        print("wash2 finished")

    async def wash3():
        await asyncio.sleep(3)
        print("wash3 finished")

    # 调用需要事件循环机制
    # step1 创建一个事件循环
    loop = asyncio.get_event_loop()

    # step2 将异步函数（协程）加入事件队列
    tasks = [
        wash1(),
        wash2(),
        wash3()
    ]

    # step3 执行事件队列 直到最晚的一个事件被处理完毕后结束
    loop.run_until_complete(asyncio.wait(tasks))

    # step4 如果不再使用loop 建议养成良好的关闭的习惯
    loop.close()