Global state versus variable shadowing (python)

README.md

Example of Shadowing versus Global Shared State in Python

$ python ./main.py
PRE-CHANGE
First (direct): I am first
First (attribute): I am first
Second (direct): I am second
Second (attribute): I am second
CHANGE 1
First (direct): I am first
First (attribute): I am first
Second (direct): I am second
Second (attribute): I am second
CHANGE 2
First (direct): I am first
First (attribute): I am first
Second (direct): I am second
Second (attribute): changed
FOLLOW-UP HYPOTHESIS
First (direct): I am first
First (attribute): changed
Second (direct): I am second
Second (attribute): changed

global_state.py

first = 'I am first'

second = 'I am second'

main.py

from __future__ import print_function

import global_state
from global_state import first, second
from mutator import change_first, change_second, change_first_alt

print('PRE-CHANGE')
print('First (direct): {}'.format(first))
print('First (attribute): {}'.format(global_state.first))
print('Second (direct): {}'.format(second))
print('Second (attribute): {}'.format(global_state.second))

change_first()

print('CHANGE 1')
print('First (direct): {}'.format(first))
print('First (attribute): {}'.format(global_state.first))
print('Second (direct): {}'.format(second))
print('Second (attribute): {}'.format(global_state.second))

change_second()
print('CHANGE 2')
print('First (direct): {}'.format(first))
print('First (attribute): {}'.format(global_state.first))
print('Second (direct): {}'.format(second))
print('Second (attribute): {}'.format(global_state.second))

change_first_alt()
print('FOLLOW-UP HYPOTHESIS')
print('First (direct): {}'.format(first))
print('First (attribute): {}'.format(global_state.first))
print('Second (direct): {}'.format(second))
print('Second (attribute): {}'.format(global_state.second))

mutator.py

import global_state
from global_state import first


def change_first():
    first = 'changed'


def change_second():
    global_state.second = 'changed'


def change_first_alt():
    global_state.first = 'changed'