Getting values from functions that run as asyncio tasks

Question

I was trying the following code:

import asyncio

@asyncio.coroutine
def func_normal():
        print(\"A\")
        yield from asyncio.sleep(5)
        print(\"B         


        

Answer 1

If you want to use any value returned by coroutine as soon as coroutine ends you can pass future object into the coro and update this future by computed value. As soon as future is updated it passes its future.result() to the callback function which is bound with given future. See code below:

import asyncio


async def func_normal(future):
    print("A")
    await asyncio.sleep(5)
    print("B")
    # return 'saad'
    future.set_result('saad')


async def func_infinite(future):
    i = 0
    while i<10:
        print("--"+str(i))
        i = i+1
    # return('saad2')
    future.set_result('saad2')

def got_result(future):
    print(future.result())

loop = asyncio.get_event_loop()
future1 = asyncio.Future()
future2 = asyncio.Future()

future1.add_done_callback(got_result)
future2.add_done_callback(got_result)

# Coros are automatically wrapped in Tasks by asyncio.wait() 
coros = [
    func_normal(future1),
    func_infinite(future2)]

loop.run_until_complete(asyncio.wait(coros))
loop.close()

The callback function is called with a single argument - the future object which it is bound with. If you need to pass more arguments into the callback use partial from functools package:

future1.add_done_callback(functools.partial(print, "future:", argin))

will call

print("future:", argin)