Good Learning Co.
SavannahYear 8
← Computing
ComputingCoding: from blocks to Python20 min★★ difficulty

Lists, functions and testing

Real programs are split into small named pieces called functions, and store groups of data in lists. Then we test them properly.

Part of your national curriculum
  • Algorithms and programming: Use a variety of data structures, including lists, tables or arrays, and design modular programs that use procedures or functions
  • Algorithms and programming: Design and develop modular programs that use procedures or functions, and test and correct them systematically

Lesson overview

What you'll learn in this lesson

Design and develop modular programs that use procedures or functions, and test and correct them systematically

Key learning points

  • • Lists
  • • Why split code up
  • • Functions
  • • Testing systematically

This lesson at a glance

  • 20 minutes
  • 18 parts to scroll through
  • 4 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

designmodularprogramsproceduresfunctions

Scroll down — the lesson carries on below

Part 1 of 18 · Intro6%
1

Introduction

Part 1 of 18

Lists, functions and testing illustrationVisual introduction

Picture this

Lists, functions and testing

Real programs are split into small named pieces called functions, and store groups of data in lists. Then we test them properly.

In a nutshell

Design and develop modular programs that use procedures or functions, and test and correct them systematically

2

What you already know

Part 2 of 18

Before we start

What you already know

You can write if statements and loops in Python.

Recap: Python decisions and loops
3

Key words

Part 3 of 18

Key words

Words you'll need today

list
An ordered collection, like animals = ["lynx", "otter", "owl"].
index
An item's position in a list. The first item is at index 0.
function
A named, reusable block of code, made with def.
test data
Values chosen to check a program works, including normal, boundary and wrong values.
4

Learning cycle

Part 4 of 18

Learning cycle 1 of 2

Part 1: Lists

A short piece of teaching, then a check to make sure it has landed.

5

Explore the idea

Part 5 of 18

Learn

Lists

animals = ["lynx", "otter", "owl"]. animals[0] is "lynx". animals.append("wolf") adds one. for a in animals: print(a) shows each one.

6

Explore the idea

Part 6 of 18

Learn

Why split code up

Breaking a big problem into smaller parts is called decomposition. Each part can be written, tested and fixed on its own.

7

Quick check

Part 7 of 18

Quick check

In ["lynx", "otter", "owl"], what is at index 1?

8

Reset break

Part 8 of 18

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now
9

Quick check

Part 9 of 18

Quick check

Splitting a problem into smaller parts is called:

10

Learning cycle

Part 10 of 18

Learning cycle 2 of 2

Part 2: Functions and testing

A short piece of teaching, then a check to make sure it has landed.

11

Explore the idea

Part 11 of 18

Learn

Functions

def greet(name): print("Hello", name) greet("Alex") runs it. Write it once, use it many times. Change it in one place and every use updates.

12

Explore the idea

Part 12 of 18

Learn

Testing systematically

For a pass mark of 50, test normal data (70), boundary data (50 and 49) and wrong data ("fish"). Write what you expect before you run each test.

13

Quick check

Part 13 of 18

Quick check

Which word creates a function in Python?

14

Quick check

Part 14 of 18

Quick check

For a pass mark of 50, which is boundary test data?

15

Common mix-ups

Part 15 of 18

Common mix-ups

Things people often get wrong

  • The first item in a list is index 0, not 1.
  • Defining a function doesn't run it. You have to call it by name.
16

Challenge round

Part 16 of 18

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

17

Mastery quiz

Part 17 of 18

Marked quiz

End of lesson quiz: Lists, functions and testing

4 questions, marked with the reasoning shown. No timer.

  1. 1. What does animals.append("wolf") do?

  2. 2. Why use functions?

  3. 3. Before running a test you should:

  4. 4. Why use a list rather than 30 separate variables for 30 test scores?

18

Lesson round-up

Part 18 of 18

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Article

How a supermarket checkout knows the price

When a barcode is scanned, the checkout does not store the price itself. It sends the barcode number to a database and reads back a record: product name, price, whether it needs an age check. The record is the single place the price lives, so changing one row changes every till in the shop at once.

Problems come from bad data, not bad scanners. If two products share a barcode, or a price update reaches the shop overnight but the till holds an old copy in its cache, customers are charged the wrong amount. Shops check this with test transactions: scan a known item, expect a known price, record what actually happened.

Good systems also log every scan. If a customer complains, the log shows exactly which record was used and when.

Written for Good Learning Co.

Reading questions

  1. Write in your own words what the checkout sends and what it receives back.
  2. Explain one way bad data could cause a wrong price, and how logging helps find it.
  3. Design a test table with four tests for a new checkout, with expected and actual results.

  • Reading and notes

    Reading

    Read the lesson text again and note the key terms and how each one is used, in your own words — as you would for revision.

    Half a page of notes

  • Extended writing

    Writing

    Explain a real system that uses this idea — how it works, where it can go wrong, and how you would make it safer or better.

    250–350 words

  • Algorithm on paper

    Diagram

    Write your steps out as pseudocode or a flowchart before you type anything, then photograph it.

    1 flowchart or 10 lines

  • Code write-up

    Writing

    Copy your code in, then explain underneath what each part does and what you had to fix.

    Code + 5 sentences

  • Test table

    Working out

    Make a test table: what you tried, what you expected, what actually happened.

    4–6 tests

Saved as you type.

Part 1 of 18 · Introduction

Playground

Python Lab

Write and run real Python

Pick a challenge, read it, predict what it will print, then press Run. Change something and run again.

How this is going

  • Not looked at yet

    Use a variety of data structures, including lists, tables or arrays, and design modular programs that use procedures or functions

  • Not looked at yet

    Design and develop modular programs that use procedures or functions, and test and correct them systematically

Good Learning Co. — personalised UK curriculum learning, built around what each learner loves.