REPEAT ... UNTIL as while True with break

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Quick Questions

Shade in the A or B circle for each question.

1. Python has no REPEAT ... UNTIL. Which is the usual way to write one?

A while True: with an if ... break at the end of the body

B do: ... while condition, written at the end

2. Pseudocode: REPEAT ... UNTIL Guess = 7. Which Python test goes at the end of the body?

A if guess == 7: break

B if guess != 7: break

3. Where does the if ... break go in a while True loop that copies REPEAT ... UNTIL?

A At the start of the loop body

B At the end of the loop body

4. How many times does the body of a while True: loop (with the break test at the end) run?

A Zero times if the condition is already True

B At least once

5. What does break do inside a while True: loop?

A Leaves the loop straight away

B Skips to the next repeat of the loop

Match the Pairs

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

Left column		Right column
1while True:		AThe condition is the wrong way round. UNTIL Num >= 1 should become if Num >= 1: break, but this stops on invalid input.
2if Guess == 7: break		Bwhile True: Age = int(input()) if Age >= 0: break
3A REPEAT loop always runs its body at least once, because the test comes at the end. In Python the body goes straight after while True:		CThe if and break are not indented, so they are outside the loop. The loop never stops and break causes an error.
4UNTIL Score >= 50 becomes an if test with the same condition, followed by break. The loop stops when this is True.		DThe end-of-loop test that copies UNTIL Guess = 7. When the condition is True, the loop stops.
5while True: Num = int(input()) if Num > 0: break		Eif Score >= 50: break
6while True: Num = int(input()) if Num < 1: break		FStarts a loop that keeps repeating until a break stops it, so the body always runs at least once. This is Python's version of REPEAT.

Definitions

while True:

Fill in the Blanks

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

while ____: name = input("Name: ") if name != "": break

while True: pin = input("PIN: ") if pin == "1234": _____

while True: score = int(input("Score: ")) if score __ 50: break

while True: n = int(input("Enter 1-10: ")) __ 1 <= n <= 10: break

_____ True: n = int(input("Number: ")) if n == 0: break

Spot the Error

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

Question 1

A while True:

B n = int(input())

C if n > 0

D break

Question 2

A while True:

B pw = input('Password: ')

C if pw = 'cat':

D break

Question 3

A total = 0

B while False:

C total += 1

D if total == 5:

E break

Question 4

A while true:

B x = int(input())

C if x >= 1 and x <= 10:

D break

Question 5

A while True:

B guess = input('Guess: '

C if guess == 'cat':

D break

Answer Key

REPEAT ... UNTIL as while True with break

Section A: Quick Questions

A — while True: with an if ... break at the end of the body

A — if guess == 7: break

B — At the end of the loop body

B — At least once

A — Leaves the loop straight away

Section B: Match the Pairs

while True: → Starts a loop that keeps repeating until a break stops it, so the body always runs at least once. This is Python's version of REPEAT.

if Guess == 7: break → The end-of-loop test that copies UNTIL Guess = 7. When the condition is True, the loop stops.

A REPEAT loop always runs its body at least once, because the test comes at the end. In Python the body goes straight after while True: → while True: Age = int(input()) if Age >= 0: break

UNTIL Score >= 50 becomes an if test with the same condition, followed by break. The loop stops when this is True. → if Score >= 50: break

while True: Num = int(input()) if Num > 0: break → The if and break are not indented, so they are outside the loop. The loop never stops and break causes an error.

while True: Num = int(input()) if Num < 1: break → The condition is the wrong way round. UNTIL Num >= 1 should become if Num >= 1: break, but this stops on invalid input.

Section C: Definitions

while True: — Python's version of REPEAT ... UNTIL: the body runs at least once, then an if with break at the end stops the loop when the UNTIL condition is True.

Section D: Fill in the Blanks

while True:
    name = input("Name: ")
    if name != "": break

while True:
    pin = input("PIN: ")
    if pin == "1234": break

while True:
    score = int(input("Score: "))
    if score >= 50: break

while True:
    n = int(input("Enter 1-10: "))
    if 1 <= n <= 10: break

while True:
    n = int(input("Number: "))
    if n == 0: break

Section E: Spot the Error

C — An if statement must end with a colon. It should be 'if n > 0:'.

C — A single = assigns a value. The UNTIL test compares two values, so it needs ==: 'if pw == 'cat':'.

B — while False never runs the body, but a REPEAT loop must run at least once. It should be 'while True:'.

A — Python's Boolean value is True with a capital T. 'true' is an undefined name and causes an error. It should be 'while True:'.

B — The closing bracket of input() is missing, which causes a syntax error. It should be " guess = input('Guess: ')".