How to call an async function during debugging?

Question

I usually like to call some functions during debugging in the console just to see some quick results. However with async functions, this doesn't seem to be possible:

import asyncio

async def func1():
    print('func1')

def func2():
    print('func2')

async def main():
    task = asyncio.create_task(func1())
    await task  # put a break point here

asyncio.run(main())

Let's say we put a break point in the line of await task Now if I call func2() in the console it will print 'func2' perfectly fine. However, if I enter await task in console, I will get the below error:

  File ".../anaconda3/lib/python3.9/asyncio/base_events.py", line 585, in _check_running
    raise RuntimeError(
RuntimeError: Cannot run the event loop while another loop is running

python 3.9 pycharm 2022.3.1

Is there any way I can call the async functions in the console like the non-async functions?

aaron · Accepted Answer · 2023-02-04 02:24:40Z

5

You can suspend the current_task and then run the event loop until the task is done.

import asyncio
from asyncio import tasks

def wait(task_or_coro):
    task = asyncio.ensure_future(task_or_coro)
    loop, current_task = task.get_loop(), tasks.current_task()
    tasks._leave_task(loop, current_task)
    while not task.done():
        loop._run_once()
    tasks._enter_task(loop, current_task)
    return task.result()

Call wait(task) instead of await task.

edited Feb 4, 2023 at 2:24

answered Feb 3, 2023 at 12:09

aaron

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3 Comments

cf1 Over a year ago

Thank you. Just curious is this the 'canonical' way of debugging async functions?

aaron Over a year ago

It depends on the scenario; this seems to be the only way to do so from a debugger (it's generally not advisable to use single-underscore functions that are "private"). For the case in the question, I wonder why you don't simply Step Over/Into?

cf1 Over a year ago

The reason that I cannot simply step into is that I often need to call those async functions out of order during debugging.

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