This document discusses modular programming in Python for ethical hackers. Modular programming breaks code into separate modules to make programs more readable, reliable, and maintainable. A module in Python is a file containing definitions and statements, and takes its name from the file name minus the .py extension. The document demonstrates creating a calculator module with add and sub functions, and importing and using those functions in a test program. It recommends several references for further reading on Python modules and programming.