fnf.py

# fire-n-forget
#
# https://bugs.python.org/issue44665
# https://bugs.python.org/issue42538 

import asyncio
import functools

running_tasks = set()


def on_done(task, n):

    print("done task " + str(n))
    exception = None

    try:
        exception = task.exception()
    except asyncio.CancelledError:
        pass

    if exception:
        # do something other than print the exception
        print(exception)

    running_tasks.remove(task)

    print(f"{len(running_tasks)} tasks left")


def schedule(async_fn, *args, **kwargs):
    n = str(args[0])
    print("scheduled " + n)
    task = asyncio.create_task(async_fn(*args, **kwargs))
    task.add_done_callback(lambda t: on_done(t, n))
    running_tasks.add(task)


def fnf(fn):
    
    @functools.wraps(fn)
    def wrapper(*args, **kwargs):

        schedule(fn, *args, **kwargs)

    return wrapper


# main.py
# from fnf import fnf


@fnf
async def task(n):

    print(f"{n} begins")

    if n % 2:
        await asyncio.sleep(n * 0.1)
        print(f"{n} ends")
        return

    await asyncio.sleep(n * 0.01)

    raise Exception("Ruh-roh " + str(n))


async def main():

    [task(n) for n in range(10)]
    await asyncio.sleep(2)
    print("done")


if __name__ == "__main__":

    asyncio.run(main())