Data Types and Strings

Every piece of data in your program has a type. The type determines what you can do with that data and how the computer stores it in memory. Think about the number "5" and the text "5". They look the same, but they're fundamentally different: They behave completely differently: The first gives 15 (mathematical addition). The second gives "510" (text concatenation). Trying text_five + 10 causes an error because you can't add text and a number directly. Data types exist because computers need to know how to interpret the 1s and 0s stored in memory. The same binary pattern could represent a number, a letter, or something else entirely, depending on its type. The Four Fundamental Types Python has many data types, but four are fundamental. Almost every program uses these: Checking Data Types Wo

About This Interactive Section

This section is part of the Python Expressions: 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.