Docstrings

When you work on a team or return to your own code after weeks or months, documentation becomes essential. Python provides docstrings, which are special strings that describe what a function does, what parameters it expects, and what it returns. Docstrings are written as the first statement in a function body using triple quotes, and Python stores them for tools and developers to access. Docstring Conventions While Python does not enforce a specific docstring format, several conventions are widely used in the industry. The Sphinx/reStructuredText style and NumPy style are particularly popular in data engineering. Here is a practical template that covers the most important information: Simple One-Line Docstrings Not every function needs extensive documentation. For simple functions with obv

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.