Libraries are collections of shared code. They're common in Python, where they're also called "modules," but they're also ...

How to use cProfile The cProfile module gathers statistics about the execution time of a Python program. It can report on anything from the entire app to a single statement or expression.

This post explains what a Python module is and how to use it to drastically extend the capabiltiies of your code. Plus: how to make your own!