Choosing a for loop or a while loop (Python)

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Date:

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Quick Questions

Shade in the A or B circle for each question.

1. You want to print a message exactly 10 times. Which loop fits best?

A while True:

B for i in range(10):

2. A program keeps asking for a password until the user types the right one. Which loop fits best?

A for

B while

3. True or false: a for loop is a good choice when you know how many times to repeat.

A True

B False

4. Which task is best for a while loop?

A Keep asking for a word until the user types quit

B Print the numbers 1 to 5

5. Which loop is best for printing the 5 times table from 1 to 12?

A for n in range(1, 13):

B while answer != 'quit':

Match the Pairs

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

Left column		Right column
1for i in range(10): print(i)		AA while loop: use it when repeating depends on a condition that can change, like until the user types quit
2while answer != "quit": answer = input("> ")		BA while loop needs a condition that can change, not range(). For a fixed count of 10, use a for loop: for i in range(10):
3You know in advance that you want to repeat exactly 5 times, so choose a for loop		Cfor turn in range(5):
4A while loop may run zero times if its condition is False the very first time it is checked		DA for loop: use it when you know the loop must run a fixed number of times, such as 10
5while i in range(10): print(i)		EA for loop cannot repeat until a condition changes. Use while answer != "quit": because we do not know how many times the user will type.
6for answer != "quit": answer = input("> ")		Flives = 0 while lives > 0:

Definitions

for vs while

Fill in the Blanks

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

___ i in range(10): print("Hello")

command = input("Command: ") _____ command != "quit": command = input("Command: ")

for i in range(_): print("Hi") print("Done")

word = "" while word __ "quit": word = input("Type: ")

# Show Go! 10 times for i in range(__): print("Go!")

Spot the Error

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

Question 1

A count = 0

B for count < 10:

C print(count)

D count += 1

Question 2

A text = ''

B while text == 'quit':

C text = input('Type: ')

D print('Bye')

Question 3

A answer = ''

B while answer != 'quit':

C input('> ')

D print('Goodbye')

Question 4

A n = 1

B while n <= 10:

C print(n)

D n -= 1

Question 5

A print('Lap counter')

B laps = 10

C for lap in laps:

D print(lap)

Answer Key

Choosing a for loop or a while loop (Python)

Section A: Quick Questions

B — for i in range(10):

B — while

A — True

A — Keep asking for a word until the user types quit

A — for n in range(1, 13):

Section B: Match the Pairs

for i in range(10): print(i) → A for loop: use it when you know the loop must run a fixed number of times, such as 10

while answer != "quit": answer = input("> ") → A while loop: use it when repeating depends on a condition that can change, like until the user types quit

You know in advance that you want to repeat exactly 5 times, so choose a for loop → for turn in range(5):

A while loop may run zero times if its condition is False the very first time it is checked → lives = 0 while lives > 0:

while i in range(10): print(i) → A while loop needs a condition that can change, not range(). For a fixed count of 10, use a for loop: for i in range(10):

for answer != "quit": answer = input("> ") → A for loop cannot repeat until a condition changes. Use while answer != "quit": because we do not know how many times the user will type.

Section C: Definitions

for vs while — Use for when you know how many times to repeat, like 10 times. Use while when repeating depends on a condition that can change, like until the user types quit.

Section D: Fill in the Blanks

for i in range(10):
    print("Hello")

command = input("Command: ")
while command != "quit":
    command = input("Command: ")

for i in range(0):
    print("Hi")
print("Done")

word = ""
while word != "quit":
    word = input("Type: ")

# Show Go! 10 times
for i in range(10):
    print("Go!")

Section E: Spot the Error

B — A for loop goes through a sequence such as range(10). It cannot take a condition. Either use 'while count < 10:' or write 'for count in range(10):'.

B — The loop should keep going until the user types quit, so the condition must be text != 'quit'. With == the condition is False at the start, so the loop never runs.

C — The typed value is thrown away, so answer never changes and the while condition stays True forever. The line should be 'answer = input('> ')'.

D — n goes down instead of up, so n <= 10 is always True and the loop never ends. A while loop must change its condition variable: n += 1.

C — laps is a single number, so a for loop cannot go through it and Python raises a TypeError. For a fixed count, use range(laps).