Asyncio - 检查协程是否在事件循环中具有特定参数的方法？

Question

In my app I have multiple classes which could have cause to add a coroutine to an event_loop. But I don't want a coroutine to be added more than once, so I need a way to check if the coroutine is already a task in the running loop.

I have found the asyncio.Task.all_tasks(loop) class method. I thought this would solve my problem but the output gives only the coroutine names and not the arguments. This is a problem for me because I am adding the same coroutine with varying sets of arguments to the event_loop.

To demonstrate:

import asyncio
from threading import Thread
from time import sleep

async def foo(a, b):
    while True:
        print("{}{}".format(a, b))
        await asyncio.sleep(1)

def loop_starter():
    loop1.create_task(foo("one","two"))
    loop1.create_task(foo("three","four"))
    loop1.run_forever()

loop1 = asyncio.new_event_loop()
t = Thread(target=loop_starter)
t.start()
sleep(0.5)
print(asyncio.Task.all_tasks(loop1))

The output of the all_tasks() method is:

{<Task pending coro=<foo() running at example.py:8> wait_for=<Future pending cb=[<TaskWakeupMethWrapper object at 0x7f7dbb312b58>()]>>, 
 <Task pending coro=<foo() running at example.py:8> wait_for=<Future pending cb=[<TaskWakeupMethWrapper object at 0x7f7dbb2a4918>()]>>}

So it appears I have no way of knowing which versions of foo are in the event loop already.

Answer 1

Only thing that comes to mind is something like this:

import asyncio


_running = list()  # set would be better if you have hashable values


def create_unique_task(coro_func, *args, **kwargs):
    loop = asyncio.get_event_loop()

    uid = (args, kwargs)
    if uid not in _running:
        task = loop.create_task(foo(*args, **kwargs))
        _running.append(uid)
        task.add_done_callback(lambda _: _running.remove(uid))
    else:
        print('skipped')
        return

    return task


async def foo(a, b):
    print("{} {}".format(a, b))
    await asyncio.sleep(0.5)


async def main():
    create_unique_task(foo, "one", "two")
    create_unique_task(foo, "three", "four")
    await asyncio.sleep(0.2)

    create_unique_task(foo, "one", "two")
    create_unique_task(foo, "three", "four")
    await asyncio.sleep(0.4)

    create_unique_task(foo, "one", "two")
    create_unique_task(foo, "three", "four")
    await asyncio.sleep(1)


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

Output:

one two
three four
skipped
skipped
one two
three four