[FIXED] await while loop in asyncio

Issue

How to await while loop? I have the following code snippet:

import asyncio
from asyncio.tasks import sleep
import time

running = True

async def f1():
    global running
    print(f"Running: {running}")
    print("f1() started.")

    ### await the while loop below
    while running:
        print(f"Inside while loop")
    ###

    print(f"Running: {running}")
    print("f1() ended")

async def f2():
    global running
    print("f2() started.")
    
    # this should be blocking code
    time.sleep(0.5)
    
    print("f2 ended.")
    running = False

async def main():
    await asyncio.gather(f1(), f2())

asyncio.run(main())

Basically, what I want is:

# 1. Start f1(). f1() has a while loop.
# 2. Start f2().
# 3. Notify f1() to break the while loop.

Solution

I guess you have to put in some await asyncio.sleep(0) or so into the while loop, not sure if it works with 0 but just put a small number. It just has to be some await call that gives others the chance to do

import asyncio
from asyncio.tasks import sleep
import time

running = True


async def f1():
    global running
    print(f"Running: {running}")
    print("f1() started.")

    ### await the while loop below
    while running:
        print(f"Inside while loop")
        await asyncio.sleep(0)
    ###

    print(f"Running: {running}")
    print("f1() ended")


async def f2():
    global running
    print("f2() started.")

    # this should be blocking code
    time.sleep(0.5)

    print("f2 ended.")
    running = False


async def main():
    await asyncio.gather(f1(), f2())


asyncio.run(main())

that works for me

Answered By - Simon Hawe