Avoid the Obstacle

A while loop keeps a robot moving until something is in the way.

🎯 What you will learn

A while loop repeats while a rule is true
The robot checks the sensor each time
Stopping safely is part of the design

👋 Let’s get started!

Some robots keep moving until something gets in the way. A while loop repeats as long as a rule is true. When the wall gets too close, the rule becomes false and the robot stops. 🧱

🪜 Step by step

1. 🔁 while

A while loop keeps going as long as its question is true.

distance = 3
while distance > 0:
    print("Still going")

2. 📉 Change a value

Each move makes the distance smaller. That changes the answer to the question.

distance = distance - 1

3. 🛑 Stop

When the question is false, the loop ends and the robot stops.

print("Stop! Wall!")

🧪 Try it!

Change the code and press ▶ Run to see what happens. You can’t break anything!

Approach the wall

distance = 30
while distance > 10:
    print("Moving. Distance:", distance)
    distance = distance - 8
print("Stop! Wall close:", distance)

🎨 Unplugged activity

🧱 With a grown-up, count down from 10 out loud while taking a step each time. What number does the loop stop at? Make a rule for when to stop.

Build a safe loop

distance = 20
while distance > 5:
    print("Move")
    distance = distance - 5
print("Stop")

📖 Key words

Tap a card to flip it over!

while: Repeat while a rule is true 🔁
Condition: The question checked each time ❓
Obstacle: Anything in the way 🧱

🏆 Challenge

Make the robot count down from 3 and print “Go!” when it reaches 0. Press ▶ Run.

Challenge

count = 3

Knowledge Check Quiz

When does a while loop stop?
What does distance = distance – 8 do?
What happens if the distance never gets small?