📒 problems 📖 glossary
Mock interview
46:30
ready
of 46:30
Lesson 3 · Foundations

This guide assumes you can already write basic Python

Plain English first: from here on, every lesson assumes you can read and write small Python programs — variables and types, if/else, loops, functions, and the everyday containers (lists, dictionaries, sets, strings), plus enough comfort to read an error message without panicking. If that already describes you, skip straight ahead to Big-O fluency and keep going.

Never written a line of code? Start with the Programming Basics guide first.

A dedicated companion course teaches programming from absolute zero, in Python — what a program is, variables, operators, conditionals, loops, functions, lists, dictionaries & sets, strings, and debugging — with runnable in-browser challenges and quiz-gated progress. Work through it, then come back here.

→ Programming Basics: learn to code from zero

Why a separate guide? Teaching programming from scratch is a full course in its own right, and folding it in here made this guide drift from its job — getting an already-coding reader interview-ready. Keeping the absolute-beginner material in its own place lets each guide do one thing well, and lets you progress along the ladder: learn to code (Programming Basics) → specialize (web / AI / security) → interview prep (this guide) → prove it by shipping projects.

Already comfortable with Python basics? Good — the next lesson, Big-O fluency, is where interview prep really begins.