Defining with def

Concepts covered: pyFuncDef

Why Use Functions? Before diving deeper into function syntax, it is important to understand why functions matter so much in professional software development. Consider a data pipeline that processes customer orders. Without functions, you might write the same validation logic in dozens of places: check if the order ID is valid, verify the customer exists, confirm the product is in stock, calculate taxes, and format the receipt. Each copy is an opportunity for bugs and inconsistencies. Function Naming Conventions Indentation: Function Body Python uses indentation to determine which code belongs to a function. Every line in the function body must be indented by the same amount, typically four spaces. This is not just a style preference; Python requires consistent indentation. When you reduce

About This Interactive Section

This section is part of the Functions: Beginner lesson on DataDriven, a free data engineering interview prep platform. Each section includes explanations, worked examples, and hands-on code challenges that execute in real time. SQL queries run against a live PostgreSQL database. Python runs in a sandboxed Docker container. Data modeling problems validate against interactive schema canvases. All content is framed around what data engineering interviewers actually test at companies like Meta, Google, Amazon, Netflix, Stripe, and Databricks.

How DataDriven Lessons Work

DataDriven combines four interview rounds (SQL, Python, Data Modeling, Pipeline Architecture) with adaptive difficulty and spaced repetition. Easy problems get harder as you improve. Weak concepts resurface until you master them. Your readiness score tracks progress across every topic interviewers test. Every lesson section ends with problems you solve by writing and running real code, not by picking multiple-choice answers.