Lesson 4 of 5 · Gardens by the Bay

Functions: a 45-minute coding lesson

A free 45-minute lesson on functions for ages 8–12. Students define plant_tree once and reuse it across Gardens by the Bay.

  • 45 minutes
  • Pairs, whole class
  • One device per pair, plus a projector
Open level 1

Learning objectives

By the end of the lesson, students can:

  • Explain that a function is a named set of instructions.
  • Define a function and call it several times.
  • Combine functions with loops to shorten a program.

Key words

Function:
A set of instructions with a name, which you can use again and again.
Define:
Teach the computer what a function name means.
Call:
Use a function by its name.

You'll need

  • One laptop, Chromebook or iPad per pair, open to dotcodecampus.com/maze/gardens/1. No accounts or installs.
  • A projector or screen for the demo.
  • Optional: the printable unplugged grid game for the warm-up, and certificates to finish.

Lesson flow

  1. Minutes 0–8

    Unplugged warm-up

    • Teach the class a three-move dance and give it a name, like "the Merlion".
    • Call out: "Merlion, clap, Merlion, jump, Merlion". Students perform it.
    • Ask: how much shorter is that than calling out every move each time? Introduce the word function.

  2. Minutes 8–15

    Demo on the projector

    • Open Gardens by the Bay level 1 (dotcodecampus.com/maze/gardens/1) and plant one tree with dig, plant, water.
    • Move to level 2. Fill the "define plant_tree" block, then use plant_tree three times.
    • Show the Python: "def plant_tree():" and point out how each tree is now one line.

  3. Minutes 15–35

    Paired play: levels 1–6

    • Pairs work through levels 1–6, swapping roles at each level.
    • Remind pairs that blocks inside "define" do nothing until the function is called.
    • Level 4 has a function with loops inside it. Suggest writing the row first and testing it.
    • Fast finishers can go for three stars everywhere to unlock "Supertree Grove".

  4. Minutes 35–42

    Class discussion

    • What changed when you moved dig, plant, water into a function?
    • If planting needed a fourth step, how many places would you change, with and without a function?
    • What everyday routines could be functions? (Make breakfast, pack a school bag.)

  5. Minutes 42–45

    Exit ticket

    • Define a function called make_kopi with three steps, then write a program that makes kopi for two people.

Early finishers: Design a garden that needs a function called plant_row, and solve it with a loop inside the function.

Answer key

One three-star solution per level, in Python. Other solutions with the same number of blocks earn three stars too. Jump links take the class straight to a level.

Level 1: First Seed

4 blocks

dotcodecampus.com/maze/gardens/1

move_right()
dig()
plant()
water()

Level 2: Teach plant_tree

11 blocks

dotcodecampus.com/maze/gardens/2

def plant_tree():
    dig()
    plant()
    water()

move_right()
plant_tree()
move_right()
move_right()
plant_tree()
move_right()
move_right()
plant_tree()

Level 3: Functions in Loops

7 blocks

dotcodecampus.com/maze/gardens/3

def plant_tree():
    dig()
    plant()
    water()

for i in range(5):
    move_right()
    plant_tree()
    move_right()

Level 4: Row by Row

10 blocks

dotcodecampus.com/maze/gardens/4

def plant_row():
    for i in range(3):
        move_right()
        dig()
        plant()
        water()
    for i in range(3):
        move_left()

for i in range(3):
    plant_row()
    move_down()

Level 5: Supertree Steps

7 blocks

dotcodecampus.com/maze/gardens/5

def plant_tree():
    dig()
    plant()
    water()

for i in range(4):
    move_right()
    plant_tree()
    move_down()

Level 6: Flower Dome Path

13 blocks

dotcodecampus.com/maze/gardens/6

def plant_tree():
    dig()
    plant()
    water()

for i in range(3):
    move_right()
    plant_tree()
    move_right()
move_down()
move_down()
for i in range(3):
    move_left()
    plant_tree()
    move_left()

Bonus: Supertree Grove

12 blocks

dotcodecampus.com/maze/gardens/bonus

def plant_tree():
    dig()
    plant()
    water()

for i in range(2):
    for j in range(4):
        move_right()
        plant_tree()
    move_down()
    for j in range(4):
        move_left()
        plant_tree()
    move_down()