CODEWITHSUNDEEP
pythonmultiprocessing
user14362977
user14362977

Reputation:

How to get function return value from a multiprocessing.Process?

I have two functions and I want to run them simultaneously. So, I tried:

from multiprocessing import Process

def func1():
    for i in range(0, 100000000):
        pass
    return 'abc'
    
def func2():
    for i in range(0, 100000000):
        pass
    return 'xyz'
    
if __name__=='__main__':
    p1 = Process(target=func1()).start()
    p2 = Process(target=func2()).start()

Now, how can I get return value of for example func1()?
I can use for example print(func1()) to get returned value but it executes the function again and it takes a long time again to execute func1(). How do I not cause the function to run again to get the result?

Upvotes: 1

Views: 2100

Answers (2)

martineau
martineau

Reputation: 123393

Here's how it could be done using a multiprocessing.Pool as I suggested in a comment.

import multiprocessing

def func1():
    for i in range(0, 100000000):
        pass
    return 'abc'

def func2():
    for i in range(0, 100000000):
        pass
    return 'xyz'

if __name__=='__main__':

    funcs = func1, func2

    with multiprocessing.Pool() as pool:
        results = [pool.apply_async(func) for func in funcs]
        pool.close()
        pool.join()

    results = [result.get() for result in results]
    print(f'{results}')  # -> ['abc', 'xyz']

Upvotes: 1

Alexander Riedel
Alexander Riedel

Reputation: 1359

you can also use the concurrent.futures module

import concurrent.futures
_pool = concurrent.futures.ThreadPoolExecutor()

def func1():
    for i in range(0, 100000000):
        pass
    return 'abc'
    
def func2():
    for i in range(0, 100000000):
        pass
    return 'xyz'
    
if __name__=='__main__':
    p1 = _pool.submit(func1)
    p2 = _pool.submit(func2)

    print(p1.result(), p2.result())

Upvotes: 0

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