Modules are like a mini program that can be dropped into your Python programs. Each module is an individual file that can be combined to create a program, app, website or whatever else you can think of. This means you can modify or edit one particular element of your app without affecting the rest (following Object Oriented Programming principals).
When you need to use code from another module in your app. Alternatively import module code within Namespaces:
from module_name import object_name
- or -
from module_name import *
to import all objects
When you import a module into python code it will only initialize once. No matter how many times you use it.