Module 3 examines the core concepts of functions and modules in Python, providing learners with the skills to write reusable, organized, and efficient code. It starts by introducing functions as the fundamental building blocks of any Python program, explaining their syntax, and guiding learners to write their first function. The module then expands on this foundation by exploring classes as blueprints for objects and demonstrating how to define and instantiate them. The DRY (Don't Repeat Yourself) principle is emphasized, highlighting the importance of code reusability and how functions achieve this. Learners will also become familiar with Python's built-in functions and engage in hands-on activities to solidify their understanding. Moving further, the module explores the practical application of functions, including defining arguments, return values, and best practices for writing efficient and readable functions. Learners will gain experience in creating custom classes with attributes and methods, applying these concepts through coding exercises. The module then challenges learners to think like programmers by breaking down real-world problems into smaller, manageable functions, fostering modularity and code organization. Finally, the module broadens the learners' toolkit by introducing built-in and external modules, explaining how to import and utilize them effectively. Learners will explore popular libraries for various tasks and gain proficiency in managing packages with pip, the Python package installer. The module culminates with a hands-on challenge where learners create their own module, demonstrating their comprehensive understanding of the concepts covered.