For loop execution model in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested for loops with break

What is the output of this Python code?

Python

result = []
for i in range(3):
    for j in range(3):
        if j == 1:
            break
        result.append((i, j))
print(result)

A [(0, 0), (1, 0), (2, 0)]

B [(0, 0), (0, 1), (1, 0), (1, 1), (2, 0), (2, 1)]

C [(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]

D [(0, 0), (1, 0), (2, 0), (2, 1)]

💡 Hint

Remember that 'break' stops the inner loop only.

The inner loop breaks when j == 1, so only j = 0 is appended for each i. The outer loop continues for i = 0, 1, 2.

❓ Predict Output

intermediate

For loop with else clause output

What will be printed by this code?

Python

for num in range(3):
    print(num)
else:
    print('Done')

A Done

B

0
1
2

C

0
1
2
Done

D

0
1
Done

💡 Hint

The else block runs if the loop completes normally.

The else block runs after the loop finishes all iterations without a break.

❓ Predict Output

advanced

Effect of modifying loop variable inside for loop

What is the output of this code?

Python

nums = [1, 2, 3]
for n in nums:
    n += 10
print(nums)

A [1, 2, 3]

B [11, 12, 13]

C [1, 12, 3]

D TypeError

💡 Hint

Changing the loop variable does not change the list elements.

The variable n is a copy of each element. Modifying n does not affect the original list.

❓ Predict Output

advanced

Loop with continue and else behavior

What will this code print?

Python

for i in range(3):
    if i == 1:
        continue
    print(i)
else:
    print('Finished')

A

0
1
2
Finished

B

0
1
2

C

0
2

D

0
2
Finished

💡 Hint

Continue skips the current iteration but does not stop the loop.

The loop skips printing 1 but continues. The else runs after the loop ends.

🧠 Conceptual

expert

Understanding for loop iteration and variable scope

Consider this code snippet. What is the value of i after the loop finishes?

Python

for i in range(5):
    pass
print(i)

A NameError

B 4

C 0

D 5

💡 Hint

The loop variable keeps the last value it had in the loop.

After the loop ends, i holds the last value from range(5), which is 4.