---
title: "Building lists from lists"
course: "PY102 · Think like a programmer"
unit: "Foundations of data structures"
lesson: 5 of 40
source: https://open.maestrocollege.edu/think-like-a-programmer/building-lists-from-lists
publisher: Maestro College
---

# Building lists from lists

Lesson 5 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
- Iterate over a list and build a new list by appending selected or transformed elements.
- Filter a list into a new list, keeping only elements that meet a condition.
- Separate the matching or transforming logic from the assembly of the result list.

## Teaching notes
Introduce the build-a-new-list pattern from scratch; do not assume students have combined iteration with append before.

## 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 5 complete: Building lists from lists."
2. Give a two-line recap of what they learned.
3. Name the next lesson, "Solving problems with arrays" (lesson 6 of 40), and give the learner its link: https://open.maestrocollege.edu/think-like-a-programmer/solving-problems-with-arrays.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: Challenge: basic array operations
Next lesson: Solving problems with arrays