I’m trying to create a test program that shares a given class object in Python 3 multiprocessing.

For doing this I create first a class object and then apply manager.Value to it in order to get the shared object.

The problem is that the shared object seems not to be the same object in memory outside and inside the process.

Any idea of what I’m doing wrong?

The code of the application is:

class MyClass:
    def __init__(self, val):
        self.val = val

    def set(self, val):
        print(f'set({val})')
        self.val= val

    def get(self):
        return self.val

def modify(args):
    shared, v = args
    print(f'prev, get()= {shared.value.get()}')
    shared.value.set(v)
    print(f'after, get()= {shared.value.get()}')

def main5():
    manager = Manager()
    myclass = MyClass(-1)
    shared = manager.Value('c', myclass)
    pool = Pool(1)
    params = []
    for v in range(5, 6):
        params.append((shared, v))
    pool.imap(func=modify, iterable=params)
    pool.close()
    pool.join()

    print("Valor modificado:", shared.value.get())

if __name__ == '__main__':
    freeze_support()
    main5()

And the output is:

prev, get()= -1
set(5)
after, get()= -1
Last value stored: -1