异步函数不异步工作

Question

我有一个问题。

我写了一个模仿http请求的简单代码：

from asyncio import sleep, run


async def get():
    print("Started get()")
    await sleep(3)
    print("Finished get()")


async def async_main():
    await get()
    await get()
    await get()


if __name__ == "__main__":
    run(async_main())

我预计结果应该是这样的：

Started get()
Started get()
Started get()
(No output, just wait 3 seconds)
Finished get()
Finished get()
Finished get()

但结果是：

Started get()
(No output, just wait 3 seconds)
Finished get()
Started get()
(No output, just wait 3 seconds)
Finished get()
Started get()
(No output, just wait 3 seconds)
Finished get()

为什么会这样？

Answer 1

您需要安排协程，显式使用 asyncio.create_task() 或隐式使用 asyncio.gather():

from asyncio import sleep, run


async def get():
    print("Started get()")
    await sleep(3)
    print("Finished get()")


async def async_main():
    tasks = [asyncio.create_task(get()), 
             asyncio.create_task(get()),
             asyncio.create_task(get())]  # Explicit
    await asyncio.gather(*tasks)

async def async_main(): # Option 2
    await asyncio.gather(get(), get(), get())  # Implicit

if __name__ == "__main__":
    run(async_main())

Answer 2

只是运行异步任务，如下所示

async def async_main():
    await asyncio.gather(get(), get(), get())

if __name__ == "__main__":
    # run(async_main()) or
    asyncio.run(async_main())

异步函数不异步工作

Async function is not working asynchronously

python

python-asyncio