[FIXED] Asyncio on long running task

Issue

I just learned async with python 3.5 yesterday.

here is what I want to accomplish today.

import asyncio  
import time
import requests

async def foo():
    """Some Long Running Taks"""
    requests.get("http://stackoverflow.com/questions/41301031/asyncio-on-long-running-task")
    print("foo")

async def bar():
    """Some Quick Task"""
    print("bar")

while True:
    loop = asyncio.get_event_loop()
    loop.run_until_complete(asyncio.gather(foo(), bar()))
    loop.close()
    time.sleep(2)

#Expected output
"""
>>>bar
>>>bar
>>>bar
>>>bar
>>>bar
>>>foo
and so on
"""

Is this possible using python async/await?

Solution

You have a few issues in your code:

1. requests does not support asyncio, use aiohttp instead.

2. Your couroutines will run only when the loop is running: Call loop.run_until_complete() only once in your code, and schedule many (short or long) tasks using await (or asycio.ensure_future() or loop.create_task()).

Here is an example doing something similar to what you were trying to do:

# make sure to run `pip install aiohttp` first!!!

import asyncio

import aiohttp


async def slow_fetch(delay):
    url = "http://httpbin.org/delay/{}".format(delay)
    print("Getting ", url)
    async with aiohttp.ClientSession() as session:
        async with session.get(url) as resp:
            text = await resp.text()
    print("Got {}, {} chars".format(url, len(text)))


async def quick_loop():
    print("enter quick_loop")
    for i in range(10):
        await asyncio.sleep(1)
        print("quick_loop", i)
    print("exit quick_loop")


loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.gather(
    slow_fetch(3),
    slow_fetch(4),
    quick_loop(),
))
loop.close()

Answered By - Udi