Synchronous call an asynchronous, callback based, function

syncc.py

#!/usr/bin/env python3
import threading
import time

def syncc(f, *args, **kwargs):
    """syncc calls the asynchronous function f with supplied
    parameters, waiting until the function callback is called, and returning
    the received parameters.
    """

    def callback(*cargs, **ckwargs):
        r.append((cargs, ckwargs))

        with cv:
            cv.notify()

    r = []
    cv = threading.Condition()
    
    with cv:
        f(*args, callback=callback, **kwargs)
        cv.wait()

    return r[0][0], r[0][1]

if __name__ == "__main__":
    def test(a, b, callback):
        print("test called with parameters {}, {} and callback {}".format(a, b, callback))

        def task():
            print("task called in a separate thread")
            time.sleep(5)

            print("task done, calling callback")
            callback(a + b)

        th = threading.Thread(target=task)
        th.start()

    r = syncc(test, 1, 2)
    print(r)