Return Values

Return vs Print: Key Diff Return Exits Immediately Each condition checks the score and returns immediately when it matches. For a score of 82, Python checks if it is invalid (no), then checks if it is 90 or above (no), then checks if it is 80 or above (yes), and immediately returns "B - Good". It never checks the remaining conditions. This pattern is efficient and easy to read. Functions Without Return

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.