Worksheet

F2.5 Count-controlled loops: for

Decisions and loops · GCSE · OCR J277 2.2.1, AQA 8525 3.2.2, Edexcel 1CP2 6.2.2 · about 15 min

What this lesson is about

range, the loop variable, and repeating a known number of times.

• for and range
• Counting from zero
• The loop variable is useful
• Loops and decisions together

Questions 9 marks in all

1. [1 mark]What does this program print?

   for i in range(4):
       print(i)

2. [1 mark]What does this program print?

   for n in range(1, 4):
       print(n, n * n)

3. [1 mark]What does this print? total = 0 then for i in range(5): total = total + i, then print(total)

4. [1 mark]A square has four sides. Which loop drives it?

   1. Afor i in range(4): with forward and turn_right(30, angle=90) inside
   2. Bfor i in range(3): with forward and turn_right(30, angle=90) inside
   3. Cfor i in range(90): with forward inside
   4. Dfor i in 4: with forward and turn_right(30, angle=90) inside

5. [1 mark]How many times does the block under for i in range(10): run?

6. [1 mark]Put the lines in order to print corner 1, corner 2, corner 3.

   Number the lines 1 to 3 to put them in the right order.

   1. for i in range(3):
   2. print("corner", corner)
   3. corner = i + 1

7. [1 mark]What does this program print?

   for n in range(0, 20, 5):
       print(n)

8. [1 mark]In OCR's Reference Language, for i = 1 to 5 ... next i. How many times does the loop run?

9. [1 mark]What does AQA call a count-controlled loop?

   1. ADefinite iteration
   2. BIndefinite iteration
   3. CSelection
   4. DRecursion

The task: count the corners

Drive a square of 30 cm sides with a for loop, printing corner 1, corner 2, corner 3, corner 4 as you go, and finish facing the way you started.

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

for i in range(4):
    forward(60, distance=30)

Plan your program here, then type it in and press Run.

Do it on the robot
www.bugbotlab.com/learn/f2-5-count-controlled-loops-for/
The simulator checks it and tells you when it passes. Nothing to install, no account.

Challenges

1. Draw a triangle with a for loop (three sides, turn_right(30, angle=120)).
2. Blink the LED five times using wait(0.2) inside a loop.
3. Print the 7 times table, from 7 to 70, with one loop.