如何将协程添加到运行 asyncio 循环？

Question

如何将新协程添加到运行 asyncio 循环中？ IE。已经在执行一组协程的一个。

我想作为一种解决方法，可以等待现有协程完成，然后初始化一个新循环（使用额外的协程）。但是有没有更好的方法呢？

Answer 1

您可以使用 create_task 来安排新协程：

import asyncio

async def cor1():
    ...

async def cor2():
    ...

async def main(loop):
    await asyncio.sleep(0)
    t1 = loop.create_task(cor1())
    await cor2()
    await t1

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

Answer 2

您的问题非常接近"How to add function call to running program?"

你什么时候需要向事件循环添加新协程？

让我们看一些例子。这里的程序用两个协程并行启动事件循环：

import asyncio
from random import randint


async def coro1():
    res = randint(0,3)
    await asyncio.sleep(res)
    print('coro1 finished with output {}'.format(res))
    return res

async def main():
    await asyncio.gather(
        coro1(),
        coro1()
    ) # here we have two coroutines running parallely

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

输出：

coro1 finished with output 1
coro1 finished with output 2
[Finished in 2.2s]

您可能需要添加一些协程来获取 coro1 的结果并在准备就绪后立即使用它？在那种情况下，只需创建等待 coro1 的协程并使用它的返回值：

import asyncio
from random import randint


async def coro1():
    res = randint(0,3)
    await asyncio.sleep(res)
    print('coro1 finished with output {}'.format(res))
    return res

async def coro2():
    res = await coro1()
    res = res * res
    await asyncio.sleep(res)
    print('coro2 finished with output {}'.format(res))
    return res

async def main():
    await asyncio.gather(
        coro2(),
        coro2()
    ) # here we have two coroutines running parallely

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

输出：

coro1 finished with output 1
coro2 finished with output 1
coro1 finished with output 3
coro2 finished with output 9
[Finished in 12.2s]

将协同程序视为具有特定语法的常规函数。您可以启动一些函数集来并行执行（通过asyncio.gather），您可以在第一次完成后启动下一个函数，您可以创建调用其他函数的新函数。

Answer 3

要将函数添加到已经运行的事件循环中，您可以使用：

asyncio.ensure_future(my_coro())

在我的例子中，我使用多线程 (threading) 和 asyncio 并想向已经运行的事件循环添加一个任务。对于处于相同情况的其他任何人，请务必明确说明事件循环（因为 Thread 中不存在事件循环）。即：

在全球范围内：

event_loop = asyncio.get_event_loop()

然后，在您的 Thread 中：

asyncio.ensure_future(my_coro(), loop=event_loop)

Answer 4

None 这里的答案似乎完全回答了这个问题。通过让“父”任务为您完成，可以将任务添加到运行事件循环。我不确定什么是最 pythonic 的方式来确保父级在它的子级全部完成之前不会结束（假设这是你想要的行为），但这确实有效。

import asyncio
import random


async def add_event(n):
    print('starting ' + str(n))
    await asyncio.sleep(n)
    print('ending ' + str(n))
    return n


async def main(loop):

    added_tasks = []

    delays = list(range(5))

    # shuffle to simulate unknown run times
    random.shuffle(delays)

    for n in delays:
        print('adding ' + str(n))
        task = loop.create_task(add_event(n))
        added_tasks.append(task)
        await asyncio.sleep(0)

    print('done adding tasks')

    results = await asyncio.gather(*added_tasks)
    print('done running tasks')

    return results


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

Answer 5

如果任务是将一个或多个协程添加到一个已经在执行一些协程的循环中，那么你可以使用我的这个解决方案

import asyncio
import time
from threading import Thread

from random import randint


# first, we need a loop running in a parallel Thread
class AsyncLoopThread(Thread):
    def __init__(self):
        super().__init__(daemon=True)
        self.loop = asyncio.new_event_loop()

    def run(self):
        asyncio.set_event_loop(self.loop)
        self.loop.run_forever()


# example coroutine
async def coroutine(num, sec):
    await asyncio.sleep(sec)
    print(f'Coro {num} has finished')


if __name__ == '__main__':
    # init a loop in another Thread
    loop_handler = AsyncLoopThread()
    loop_handler.start()

    # adding first 5 coros
    for i in range(5):
        print(f'Add Coro {i} to the loop')
        asyncio.run_coroutine_threadsafe(coroutine(i, randint(3, 5)), loop_handler.loop)

    time.sleep(3)
    print('Adding 5 more coros')

    # adding 5 more coros
    for i in range(5, 10):
        print(f'Add Coro {i} to the loop')
        asyncio.run_coroutine_threadsafe(coroutine(i, randint(3, 5)), loop_handler.loop)

    # let them all finish
    time.sleep(60)

执行此示例后，我们将得到以下输出：

Add Coro 0 to the loop
Add Coro 1 to the loop
Add Coro 2 to the loop
Add Coro 3 to the loop
Add Coro 4 to the loop
Coro 0 has finished
Adding 5 more coros
Add Coro 5 to the loop
Add Coro 6 to the loop
Add Coro 7 to the loop
Add Coro 8 to the loop
Add Coro 9 to the loop
Coro 1 has finished
Coro 3 has finished
Coro 2 has finished
Coro 4 has finished
Coro 9 has finished
Coro 5 has finished
Coro 7 has finished
Coro 6 has finished
Coro 8 has finished

Process finished with exit code 0

如何将协程添加到运行 asyncio 循环？

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how to add a coroutine to a running asyncio loop?

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如何将协程添加到运行 asyncio 循环？