How do I share global variables across modules?

The canonical way to share information across modules within a single program is to create a special module (often called config or cfg). Just import the config 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. For example: 

config.py: 
x = 0 # Default value of the 'x' configuration setting 
mod.py: 
import config
config.x = 1