How to make event loop run task concurrently?

Question

I want to call two function concurrently in asyncio , I do it with loop.create_task , but I find that it is not concurrently actually.

Here is my code:

import asyncio


async def foo(v):
    print(f"start {v}")
    for i in range(5):
        print(f"work in {v}")
    print(f"done {v}")


def schedule_foo():
    print("out start 1")
    loop.create_task(foo(1))
    print("out start 2")
    loop.create_task(foo(2))


loop = asyncio.get_event_loop()
schedule_foo()
loop.run_forever()

this will output:

out start 1
out start 2
start 1
work in 1
work in 1
work in 1
work in 1
work in 1
done 1
start 2
work in 2
work in 2
work in 2
work in 2
work in 2
done 2

As you can see the main loop is async, but sub task is actually sync.

My question is how can I make the function run in concurrently actually ?

Answer 1

You forgot to use await :

import asyncio

async def foo(v):
    print(f"start {v}")
    for i in range(5):
        print(f"work in {v}")
        await asyncio.sleep(0.1)
    print(f"done {v}")


def schedule_foo():
    print("out start 1")
    loop.create_task(foo(1))
    print("out start 2")
    loop.create_task(foo(2))


loop = asyncio.get_event_loop()
schedule_foo()
loop.run_forever()