Lesson 6 of 12

Loops: do it again

Learn loops with flowchart blocks: Repeat a set number of times, Count with a number each lap, and Repeat While until something changes. Run every one.

About 7 minutes · 4 parts, each with a program to try

Part 1 of 4

Repeat: a set number of times

Repeat runs the blocks on its body arrow again and again, then carries on down its exit arrow.

Use it when you know how many times: say it 3 times.

ExampleThree cheers Try it

Start
Repeat 3 times
Repeat →
1. Tell "Hip hip hooray!"
back to the top for the next lap
End

It showsHip hip hooray!Hip hip hooray!Hip hip hooray!

1for _ in range(3):2    print("Hip hip hooray!")

Part 2 of 4

Count: a number for each lap

Count is a repeat with a number that goes up each time, like i from 1 to 5.

In code this is a for loop.

ExampleFive laps Try it

Start
Count i from 1 to 5
Repeat →
1. Tell "Lap " + i
back to the top for the next lap
End

It showsLap 1Lap 2Lap 3Lap 4Lap 5

1for i in range(1, 6):2    print("Lap " + str(i))

Part 3 of 4

Repeat While: until something changes

Repeat While keeps going for as long as its condition is true. Use it when you don't know how many times.

Something inside must change the value it checks, or it never stops.

ExampleSaving up Try it

Start
Create savings = 0
Create weeks = 0
Repeat while savings < 100
Repeat →
1. Change savings to savings + 30
2. Change weeks to weeks + 1
back to the top for the next lap
Tell "After " + weeks + " weeks you have " + savings
End

It showsAfter 4 weeks you have 120

1savings = 02weeks = 03while savings < 100:4    savings = savings + 305    weeks = weeks + 16print("After " + str(weeks) + " weeks you have " + str(savings))

Part 4 of 4

Add things up in a loop

Start a total at 0, and add to it each lap. This is one of the most useful patterns in programming.

ExampleAdd 1 to 10 Try it

Start
Create total = 0
Count i from 1 to 10
Repeat →
1. Change total to total + i
back to the top for the next lap
Tell "1 + 2 + ... + 10 = " + total
End

It shows1 + 2 + ... + 10 = 55

1total = 02for i in range(1, 11):3    total = total + i4print("1 + 2 + ... + 10 = " + str(total))

Blocks in this lesson

Repeat Count Repeat While

Quick check

How many times does Count i from 2 to 6 run?

Practise this

World 3 challengesBuild it yourself, with three hints each.🚦 Traffic LightA Story Mode story that uses it.