---
title: "Arrays and indexing"
course: "PY102 · Think like a programmer"
unit: "Foundations of data structures"
lesson: 2 of 40
source: https://open.maestrocollege.edu/think-like-a-programmer/arrays-and-indexing
publisher: Maestro College
---

# Arrays and indexing

Lesson 2 of 40 in **Think like a programmer** (PY102), unit "Foundations of data structures". An open lesson from Maestro College.

## What the learner will be able to do
- Identify arrays as ordered, index-based collections and relate them to Python lists.
- Access elements by index and validate index boundaries, recognizing out-of-range conditions.
- Add new elements to an existing array.

## Teaching notes
Fast refresher: students already know Python list indexing from PY101, so move quickly and focus on framing arrays as an index-based structure.

## Course teaching approach
- Start from a real-world problem, then introduce the concept as the solution.
- Keep it true beginner level, hands-on, a little gamified. The learner should feel they are winning.
- Balance explanation, demonstration and practice. No copy-paste exercises: give small story-based tasks.
- End with one fun closed question about the topic.

## How to use this document
You are acting as a tutor for a learner on Maestro Open. Teach from this document, one small step at a time. Ask the learner to try things, wait for their answer, then give feedback. Keep it beginner-friendly. If the lesson involves code or spreadsheets and you cannot run them, ask the learner to try it on their own computer and paste the result back. Do not award grades, credit or certificates.

## When the lesson is done
The lesson is complete only when the learner has shown they can do every outcome listed above. Check each one with a small task or question; if an answer is wrong, explain and let them try again before moving on.
When every outcome is covered:
1. Say clearly: "Lesson 2 complete: Arrays and indexing."
2. Give a two-line recap of what they learned.
3. Name the next lesson, "How updates and removals reshape a structure" (lesson 3 of 40), and give the learner its link: https://open.maestrocollege.edu/think-like-a-programmer/how-updates-and-removals-reshape-a-structure.md. Tell them to paste that page into this chat, or fetch it yourself if you can open links, then start it the same way. Do not start teaching the next lesson's topic until the learner has it.

Previous lesson: What is a data structure?
Next lesson: How updates and removals reshape a structure