python - 属性错误 : module 'asyncio' has no attribute 'create_task'

Question

我正在尝试 asyncio.create_task() 但我正在处理这个错误:

这是一个例子:

import asyncio
import time

async def async_say(delay, msg):
    await asyncio.sleep(delay)
    print(msg)

async def main():
    task1 = asyncio.create_task(async_say(4, 'hello'))
    task2 = asyncio.create_task(async_say(6, 'world'))

    print(f"started at {time.strftime('%X')}")
    await task1
    await task2
    print(f"finished at {time.strftime('%X')}")

loop = asyncio.get_event_loop()
loop.run_until_complete(main())

输出:

AttributeError: module 'asyncio' has no attribute 'create_task'

---

所以我尝试使用以下代码片段 (.ensure_future())，没有任何问题:

async def main():
    task1 = asyncio.ensure_future(async_say(4, 'hello'))
    task2 = asyncio.ensure_future(async_say(6, 'world'))

    print(f"started at {time.strftime('%X')}")
    await task1
    await task2
    print(f"finished at {time.strftime('%X')}")

loop = asyncio.get_event_loop()
loop.run_until_complete(main())

输出:

started at 13:19:44
hello
world
finished at 13:19:50

---

怎么了？

---

[注意]:

• Python 3.6
• Ubuntu 16.04

---

[更新]:

借自 _{@ user4815162342} Answer ，我的问题解决了:

async def main():
    loop = asyncio.get_event_loop()
    task1 = loop.create_task(async_say(4, 'hello'))
    task2 = loop.create_task(async_say(6, 'world'))

    print(f"started at {time.strftime('%X')}")
    await task1
    await task2
    print(f"finished at {time.strftime('%X')}")

loop = asyncio.get_event_loop()
loop.run_until_complete(main())

Answer 1

create_task顶级函数是在 Python 3.7 中添加的，而您使用的是 Python 3.6。在 3.7 之前，create_task 只能作为 method 使用。在事件循环中，所以你可以这样调用它:

async def main():
    loop = asyncio.get_event_loop()
    task1 = loop.create_task(async_say(4, 'hello'))
    task2 = loop.create_task(async_say(6, 'world'))
    # ...
    await task1
    await task2

这在 3.6 和 3.7 以及早期版本中都有效。 asyncio.ensure_future也会工作，但是当你知道你正在处理协程时，create_task 更明确并且是 preferred选项。