Asyncio 不异步执行任务

Question

我正在使用asyncioPython 模块，但我不知道我的简单代码有什么问题。它不会异步执行任务。

#!/usr/bin/env python3    

import asyncio
import string    


async def print_num():
    for x in range(0, 10):
        print('Number: {}'.format(x))
        await asyncio.sleep(1)    

    print('print_num is finished!')    

async def print_alp():
    my_list = string.ascii_uppercase    

    for x in my_list:
        print('Letter: {}'.format(x))
        await asyncio.sleep(1)    

    print('print_alp is finished!')    


async def msg(my_msg):
    print(my_msg)
    await asyncio.sleep(1)    


async def main():
    await msg('Hello World!')
    await print_alp()
    await msg('Hello Again!')
    await print_num()    


if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())
    loop.close()

这是调用脚本时的输出：

Hello World!
Letter: A
Letter: B
Letter: C
Letter: D
Letter: E
Letter: F
Letter: G
Letter: H
Letter: I
Letter: J
Letter: K
Letter: L
Letter: M
Letter: N
Letter: O
Letter: P
Letter: Q
Letter: R
Letter: S
Letter: T
Letter: U
Letter: V
Letter: W
Letter: X
Letter: Y
Letter: Z
print_alp is finished!
Hello Again!
Number: 0
Number: 1
Number: 2
Number: 3
Number: 4
Number: 5
Number: 6
Number: 7
Number: 8
Number: 9
print_num is finished!

Answer 1

您按顺序调用函数，因此代码也按顺序执行。请记住，这await this意味着“执行this并等待它返回”（但与此同时，如果this选择暂停执行，则可能会运行其他地方已经启动的其他任务）。

如果您想异步运行任务，您需要：

async def main():
    await msg('Hello World!')
    task1 = asyncio.ensure_future(print_alp())
    task2 = asyncio.ensure_future(print_num())
    await asyncio.gather(task1, task2)
    await msg('Hello Again!')

另请参阅该函数的文档asyncio.gather。或者，您也可以使用asyncio.wait.