How can I share values between multiprocess?

Question

How can I send a value which in a process to another process? For example I have something like this code piece. I want to print value in xFunc. Can someone explain how can I do it? Thank you.

def yFunc():
    value = 5

def xFunc():
    print(value)

def smap(f):
    return f()

def main():
    f_x = functools.partial(xFunc)
    f_y = functools.partial(yFunc)

    with Pool() as pool:
        res = pool.map(smap, [f_x, f_y])


if __name__ == '__main__':
    main()

Edit: value is not constant number it is changing continuously.

Edit2: I found a way for my problem. Here the solution:

https://stackoverflow.com/a/58208695/16660763

I need to use processes because I tested both processes and threads to measure time. Processes are much faster for my script. — CocoCoder41, Aug 16 '21 at 23:55
Did you look at this: https://stackoverflow.com/questions/38322574/python-multiprocessing-sharing-of-global-values ? — Chaos_Is_Harmony, Aug 16 '21 at 23:57

score 0 · Answer 1 · answered Aug 16 '21 at 23:56

0

There are several ways. One way would be to use the global keyword. like this:

def yFunc():
    global value
    value = 5

def xFunc():
    print(value + 1)

yFunc()
xFunc()

Or like this:

value = 5

def yFunc():
    global value
    value = value + 1

def xFunc():
    print(value)

yFunc()
xFunc()

Another way would be to pass the variable to the function like this:

def yFunc():
    value = 5
    return value

def xFunc(x):
    print(x)

xFunc(yFunc())

Hope that's what you were asking.

answered Aug 16 '21 at 23:56

d6stringer

71
1
10

Thank you for your answer, I will try it. – CocoCoder41 Aug 17 '21 at 00:16
Unfortunately, I couldn't use these methods with multiprocess. – CocoCoder41 Aug 17 '21 at 01:01
There are no globals that are shared between processes — so this will not work. – martineau Aug 17 '21 at 01:16

score 0 · Answer 2 · answered Aug 18 '21 at 00:13

0

Python has provided some tools to realize it.

Considering Pipes, Queues, Value and Managers.

answered Aug 18 '21 at 00:13

Jay

738
8
14

Yes, I solved by using Managers(). Thank you. – CocoCoder41 Aug 18 '21 at 00:18
If you need to share "simple" values such as integers, then you should use a shared memory implementation such as a [Value](https://docs.python.org/3/library/multiprocessing.html#shared-ctypes-objects) rather than a managed type for efficiency. – Booboo Aug 19 '21 at 10:18

How can I share values between multiprocess?

2 Answers2