Two independent async loops in Python

Question

What would be a good approach to execute two asynchronous loops running in parallel in Python, using async/await?

I've thought about something like the code below, but can't wrap my head around how to use async/await/EventLoop in this particular case.

import asyncio

my_list = []

def notify():
    length = len(my_list)
    print("List has changed!", length)

async def append_task():
    while True:
        time.sleep(1)
        await my_list.append(random.random())
        notify()

async def pop_task():
    while True:
        time.sleep(1.8)
        await my_list.pop()
        notify()

loop = asyncio.get_event_loop()
loop.create_task(append_task())
loop.create_task(pop_task())
loop.run_forever()

Expected output:

$ python prog.py
List has changed! 1 # after 1sec
List has changed! 0 # after 1.8sec
List has changed! 1 # after 2sec
List has changed! 2 # after 3sec
List has changed! 1 # after 3.6sec
List has changed! 2 # after 4sec
List has changed! 3 # after 5sec
List has changed! 2 # after 5.4sec

Answer 1

this works fine:

note: you wanted to await fast non-io bound operations (list.append and list.pop that are not even coroutines); what you can do is awaitasyncio.sleep(...) (which is a coroutine and yield control back to the caller):

import asyncio
import random

my_list = []


def notify():
    length = len(my_list)
    print("List has changed!", length)

async def append_task():
    while True:
        await asyncio.sleep(1)
        my_list.append(random.random())
        notify()

async def pop_task():
    while True:
        await asyncio.sleep(1.8)
        my_list.pop()
        notify()


loop = asyncio.get_event_loop()
cors = asyncio.wait([append_task(), pop_task()])
loop.run_until_complete(cors)

time.sleep itself is blocking and does not play nicely with await.