Scratch forever and repeat until blocks as while loops

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Quick Questions

Shade in the A or B circle for each question.

1. Which Python line matches the Scratch forever block?

A while True:

B for True:

2. Which Python line matches the Scratch block: repeat until score = 10?

A while not score == 10:

B while score == 10:

3. A while True: loop will stop by itself after a few turns.

A True

B False

4. How do you stop a while True: loop when the player types 'quit'?

A if answer == 'quit': continue

B if answer == 'quit': break

5. A Scratch repeat until block checks its condition. When does the loop run its code?

A While the condition is still false

B While the condition is already true

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1while True:		AScratch repeat until done means keep going until done is true, so the loop needs not. This loop would stop at the start while done is False. Use while not done:
2while not done:		Bwhile not score == 10: score = score + 1
3A forever block that stops when the player presses q can be written with break inside a while True loop		CThe Python version of Scratch repeat until done. It keeps looping while done is still False and stops once done becomes True.
4Scratch repeat until score = 10 becomes a while loop that uses not		DTrue needs a capital T in Python. Writing true gives a NameError because Python does not know that name. Use while True:
5while true: print("Go!")		EThe Python version of the Scratch forever block. It repeats the indented code nonstop until a break stops it.
6while done: print("Working")		Fwhile True: key = input() if key == "q": break

Definitions

while True:

Fill in the Blanks

Complete each line of code by filling in the missing parts.

_____ True: print("Hello!")

while ____: print("Go!")

done = False while ___ done: done = True

while True: if score >= 10: _____

lives = 3 while not lives __ 0: lives = lives - 1

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A score = 0

B while True:

C score == score + 1

D if score == 5:

E break

Question 2

A while True:

B answer = input('Quit? ')

C if answer == 'yes'

D break

Question 3

A lives = 3

B while True:

C lives = lives - 1

D if lives = 0:

E break

Question 4

A energy = 3

B while True:

C energy = energy - 1

D print(energy

E if energy == 0:

F break

Question 5

A tries = 0

B found = False

C while found:

D tries = tries + 1

E found = tries == 3

Answer Key

Scratch forever and repeat until blocks as while loops

Section A: Quick Questions

A — while True:

A — while not score == 10:

B — False

B — if answer == 'quit': break

A — While the condition is still false

Section B: Match the Pairs

while True: → The Python version of the Scratch forever block. It repeats the indented code nonstop until a break stops it.

while not done: → The Python version of Scratch repeat until done. It keeps looping while done is still False and stops once done becomes True.

A forever block that stops when the player presses q can be written with break inside a while True loop → while True: key = input() if key == "q": break

Scratch repeat until score = 10 becomes a while loop that uses not → while not score == 10: score = score + 1

while true: print("Go!") → True needs a capital T in Python. Writing true gives a NameError because Python does not know that name. Use while True:

while done: print("Working") → Scratch repeat until done means keep going until done is true, so the loop needs not. This loop would stop at the start while done is False. Use while not done:

Section C: Definitions

while True: — The Python version of the Scratch forever block. It repeats its indented code nonstop until break. Scratch repeat until x becomes while not x:

Section D: Fill in the Blanks

while True:
    print("Hello!")

while True:
    print("Go!")

done = False
while not done:
    done = True

while True:
    if score >= 10:
        break

lives = 3
while not lives == 0:
    lives = lives - 1

Section E: Spot the Error

C — A double == compares values, so this line does not change score and the loop never reaches 5. Use a single = to assign: ' score = score + 1'.

C — An if statement must end with a colon. The line should be " if answer == 'yes':".

D — A single = assigns a value. To compare two values you need ==. The line should be ' if lives == 0:'.

D — The print() call is missing its closing bracket. It should be ' print(energy)'.

C — Scratch 'repeat until found' becomes 'while not found:'. With 'while found:' the loop never runs, because found starts as False.