I have two functions to run in parallel and each of them returns a value. I need to wait for both functions to finish and then process the returns from them. How could I achieve this in python. Assume
def fun1():
#do some calculation#
return val1
def fun2():
#do some calculation#
return val2
I want fun1 and fun2 to run in parallel and then need to calculate
valsum = val1+val2
Using concurrent.futures:
from concurrent.futures import ProcessPoolExecutor as Executor
#from concurrent.futures import ThreadPoolExecutor as Executor # to use threads
with Executor() as executor:
future1 = executor.submit(fun1, arg1, arg2, ...)
future2 = executor.submit(fun2, arg1, arg2, ...)
val1, val2 = future1.result(), future2.result()
valsum = val1 + val2
concurrent.futures.Executor.submit schedules the function to be executed, and returns a concurrent.futures.Future object.
concurrent.futures.Future.resultreturns the return value returned by the function.
Using multiprocessing.pool:
from multiprocessing.pool import Pool
#from multiprocessing.pool import ThreadPool as Pool # to use threads
with multiprocessing.pool.Pool() as pool:
result1 = pool.apply_async(fun1, (arg1, arg2, ...))
result2 = pool.apply_async(fun2, (arg1, arg2, ...))
val1, val2 = result1.get(), result2.get()
valsum = val1 + val2
multiprocessing.pool.Pool.apply_async returns an AsyncResult object, and
AsyncResult.get will return the return value of the function once it finish and the result arrive.
This is a simple example using list comprehension and calling .result() on each future which blocks until the process returns:
import concurrent.futures
def download_video(data):
# print(data)
return data
with concurrent.futures.ProcessPoolExecutor() as executor:
futures = [executor.submit(download_video, x, ) for x in your_list]
results = [result.result() for result in futures]
