I have a parent class in Python that can start a process in a child class. The child class has a multiprocessing.Process that changes some variables. I would expect changes to be visible for the parent class since the object is created there, but somehow, the variables are not shared. The process is started as a fork.

Here is an example code:

import multiprocessing
from multiprocessing import Queue, Process
import time

class Parent:
    def __init__(self):
        print(multiprocessing.get_start_method())
        self.child = Child()

    def start(self):
        self.child.start_child()

    def print_child_variable(self):
        print('Parent: Child Variable: ' + str(self.child.some_variable))


class Child:

    def __init__(self):
        self.some_variable = None
        self.status = False

    def start_child(self):
        self.status = True

        do_something_process = Process(target=self.do_something)
        do_something_process.start()
    

    def do_something(self):
        self.some_variable = True
        print('Child: some variable after changing: ' + str(self.some_variable))

    def print_some_variable(self):
        print('Child: some variable: ' + str(self.some_variable))
    

if __name__ == '__main__':
    parent = Parent()
    parent.print_child_variable()
    time.sleep(1)
    parent.start()
    parent.print_child_variable()
    time.sleep(1)
    parent.print_child_variable()
    time.sleep(1)
    parent.child.print_some_variable()

The output:

fork
Parent: Child Variable None
Parent: Child Variable None
Child: some variable after chaging True
Parent: Child Variable None
Child: some variable None

I would expect that after the change, the variable some_variable will be true even if checked from the parent object. Can anyone help me understand what is going on?