RuntimeError: This event loop is already running in python

Question

I think I\'m getting this error because my code calls asyncio.get_event_loop().run_until_complete(foo()) twice. Once from foo() and second time fr

Answer 1

Using nest_asyncio didn't work for me, because then aiohttp started complaining with

• RuntimeError: Timeout context manager should be used inside a task

Instead I decided to replace all calls to asyncio.run with calls to this asyncio_run:

def asyncio_run(future, as_task=True):
    """
    A better implementation of `asyncio.run`.

    :param future: A future or task or call of an async method.
    :param as_task: Forces the future to be scheduled as task (needed for e.g. aiohttp).
    """

    try:
        loop = asyncio.get_running_loop()
    except RuntimeError:  # no event loop running:
        loop = asyncio.new_event_loop()
        return loop.run_until_complete(_to_task(future, as_task, loop))
    else:
        nest_asyncio.apply(loop)
        return asyncio.run(_to_task(future, as_task, loop))


def _to_task(future, as_task, loop):
    if not as_task or isinstance(future, Task):
        return future
    return loop.create_task(future)

A secondary goal was to be able to think of asyncio.run as promise.resolve from the JS world, or Task.Wait from the .NET world.