How can you share global variables across modules?

The canonical way to share information across modules within a single program is to create a special configuration module (often called config or cfg). Just import the configuration module in all modules of your application; the module then becomes available as a global name. Because there is only one instance of each module, any changes made to the module object get reflected everywhere.

File: config.py

x = 0 # Default value of the 'x' configuration setting

File: mod.py

import config
config.x = 1

File: main.py

import config
import mod
print config.x

Module variables are also often used to implement the Singleton design pattern, for the same reason.