Shared array multiprocessing Python

Question

I am running a multi-process code in Python with a shared array. The problem is that I can't initialise that array...
To share an array in a multi-process program I have read I need to use multiprocessing.Array, but when I try it as in the code below it is not printing anything + I don't have error messages.

import multiprocessing
...
...
if __name__ == "__main__":
 an_array= multiprocessing.Array("i", [1,2])
 print(an_array) # why does it not print anything? I was expecting to print [1,2]
 p1 = multiprocessing.Process(target=function1, args = [an_array, 3]

• Chiheb Nexus: Which python version are you using ? Also, i can't reproduce this behaviour and your code will not print [1, 2] but i'll print anothing thing.
• tdelaney: Can you turn this into a short working example?
• tdelaney: After fixing the syntax errors your code prints <SynchronizedArray wrapper for <multiprocessing.sharedctypes.c_int_Array_2 object at 0x7f7bbc63df28>>. I am running Ubuntu.
• tdelaney: Can you include your operating system and how you run this code (eg, command line, jupyter, etc...)?

Answer 1

To print elements inside the Array do the following:

import multiprocessing
if __name__ == '__main__':
 an_array = multiprocessing.Array("i", [1, 2])
 # first choice to print element in Array:
 for element in an_array:
 print(element)
 # second choice to print elements in Array:
 print(an_array[:])
 # third choice to print elements in Array:
 print(list(an_array[:]))