multiprocessing global variable updates not returned to parent

Question

I am trying to return values from subprocesses but these values are unfortunately unpicklable. So I used global variables in threads module with success but have not been ab

Answer 1

You could also use a multiprocessing Array. This allows you to have a shared state between processes and is probably the closest thing to a global variable.

At the top of main, declare an Array. The first argument 'i' says it will be integers. The second argument gives the initial values:

shared_dataDV03 = multiprocessing.Array ('i', (0, 0)) #a shared array

Then pass this array to the process as an argument:

j = multiprocessing.Process(target=getDV03CclDrivers, args=('LORR',shared_dataDV03))

You have to receive the array argument in the function being called, and then you can modify it within the function:

def getDV03CclDrivers(lib,arr):  # call global variable
    arr[1]=1
    arr[0]=0

The array is shared with the parent, so you can print out the values at the end in the parent:

print 'DV03', shared_dataDV03[:]

And it will show the changes:

DV03 [0, 1]