Multiple Assignment

Python allows assigning multiple variables simultaneously. This isn't just syntactic sugar; it's essential for many algorithmic patterns. Understanding how it works internally helps you avoid subtle bugs. Swapping Without Temp Vars In most languages, swapping two variables requires a temporary variable. Python evaluates the right side completely before assigning, enabling direct swaps: This works because Python evaluates (b, a) as a tuple first, THEN unpacks it into (a, b). This pattern is critical for in-place array algorithms like reversing, rotating, or partitioning: Reverse an Array In-Place Cycle Detection (Floyd's Algorithm) Parallel Assignment Initialize multiple variables on one line. All values on the right are evaluated before any assignment occurs: Two pointers pattern: Sequence

About This Interactive Section

This section is part of the Python Expressions: Advanced 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.