并行化python中的函数调用

Question

I have a function in python which I need to execute it multiple times and at the same time (to save computational cost). The following is a simple example and I don't know how to call my function at the same time!

def f(x):
    return x

y1=f(x1)
y2=f(x2)

I need to execute y1 and y2 at the same time and wait until both finish and save the results. Thank you all in advance.

Answer 1

I would encourage you to read the https://docs.python.org/3/library/multiprocessing.html documentation, which has a great example. If you're using Python 3.x

from multiprocessing import Pool
def f(x):
    return x*x

if __name__ == '__main__':
    with Pool(5) as p:
        print(p.map(f, [1, 2, 3]))

If you're using python 2.7: https://docs.python.org/2.7/library/multiprocessing.html

from multiprocessing import Pool

def f(x):
    return x*x

if __name__ == '__main__':
    p = Pool(5)
    print(p.map(f, [1, 2, 3]))

Answer 2

Another solution that might help you:

import Queue
import threading

# your function with a slight change:
def f(q,x):
    q.put(x)

inputs = [1,2,3,4]

# aggregate to a queue:
q = Queue.Queue()

for x in inputs:
    t = threading.Thread(target=f, args=(q,x))
    t.daemon = True
    t.start()

outputs = q.get()
print outputs

output: 1

Here q holds the return value of f .

In any case I suggest you try and read this .