Scope and Variables

Scope determines where a variable exists and can be accessed. Understanding scope prevents bugs where variables unexpectedly have wrong values or do not exist when you expect them to. Python has two main scopes relevant to functions: local scope (inside a function) and global scope (outside all functions). Local Variables Variables created inside a function are local to that function. They are created when the function starts running and destroyed when the function finishes. They do not exist outside the function and cannot be accessed from elsewhere: This isolation is intentional and beneficial. Each function has its own private workspace. You can use the same variable name in different functions without conflict because each function has its own local scope. Global Variables Variables cr

About This Interactive Section

This section is part of the Functional Programming: 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.