Functions

Functions let you package code into reusable units. Instead of repeating the same logic, you define it once and call it whenever needed. Defining Functions Steps to Define a Function Building a function follows a consistent pattern. Each step adds a layer of clarity to how the function works. Parameters are the variable names in the function definition. Arguments are the actual values you pass when calling the function. Keyword arguments allow callers to pass values by name, making function calls self-documenting and removing the need to remember argument order. Functions are first-class objects in Python. You can assign them to variables, pass them as arguments to other functions, and return them from other functions.

About This Interactive Section

This section is part of the Python Foundations: Intermediate 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.