Counter-based while loop in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple counter-based while loop

What is the output of this Python code?

Python

count = 0
while count < 3:
    print(count)
    count += 1

A

1
2

B

1
2
3

C

0
1
2
3

D

0
1
2

💡 Hint

Remember, the loop runs while count is less than 3, starting from 0.

The loop starts at 0 and prints count before increasing it by 1. It stops before count reaches 3, so it prints 0, 1, and 2.

❓ Predict Output

intermediate

Value of counter after loop ends

What is the value of variable 'counter' after this code runs?

Python

counter = 5
while counter > 0:
    counter -= 2

A 0

B -1

C 1

D 2

💡 Hint

Check how counter changes each loop iteration until the condition fails.

Starting at 5, counter decreases by 2 each time: 5 -> 3 -> 1 -> -1. The loop stops when counter is no longer > 0, so final value is -1.

🔧 Debug

advanced

Identify the error in this counter-based while loop

What error does this code produce when run?

Python

i = 0
while i < 5:
    print(i)
    i += 1

A SyntaxError

B TypeError

C IndentationError

D NameError

💡 Hint

Check the syntax of the while statement line.

The while statement is missing a colon at the end, causing a SyntaxError.

❓ Predict Output

advanced

Output of a while loop with break and counter

What is the output of this code?

Python

count = 0
while True:
    if count == 3:
        break
    print(count)
    count += 1

A

1
2
3

B

0
1
2
3

C

0
1
2

D

0
1
2
3
4

💡 Hint

The loop breaks when count reaches 3, so it does not print 3.

The loop prints count starting at 0 and stops before printing 3 because of the break.

❓ Predict Output

expert

Final value of counter with complex condition

What is the final value of 'counter' after this code runs?

Python

counter = 10
while counter > 0:
    counter -= 3
    if counter == 4:
        counter += 1

A -1

B 1

C 0

D 4

💡 Hint

Track the counter value each loop iteration carefully.

The counter decreases by 3 each time: 10 -> 7 -> 4. When counter is 4, it increases by 1 to 5, then continues: 5 -> 2 -> -1. The loop stops when counter is no longer > 0, so final value is -1 after last decrement.