background.py

from multiprocessing import Process,Queue
import time
def queued(q,f,*args,**kwargs):
    q.put(f(*args,**kwargs))
def res(a):
    return next(a)
def gen(f,*args,**kwargs):
    q = Queue()
    p = Process(target=queued,args=(q,f,*args),kwargs=kwargs)
    yield p.start()
    yield [q.get(),p.join()][0]
def calc(f,*args,**kwargs):
    g=gen(f,*args,**kwargs)
    next(g)
    return g
############################# DEMO/TEST #####################################
def test(a):
    print("start calc")
    time.sleep(2)
    print("done calc")
    return a*a
a=calc(test,a=5)
print("long current calculation")
time.sleep(1)
print("long current calculation")
time.sleep(1)
print("long current calculation")
res(a)