While–else behavior in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of while–else with break

What is the output of this Python code?

Python

i = 0
while i < 3:
    if i == 1:
        break
    print(i)
    i += 1
else:
    print('Done')

A 0\n1

B 0\nDone

C 0\n1\nDone

D 0

💡 Hint

Remember that the else block runs only if the loop completes without break.

The loop breaks when i == 1, so the else block does not run. Only 0 is printed.

❓ Predict Output

intermediate

While–else without break

What will this code print?

Python

count = 0
while count < 2:
    print(count)
    count += 1
else:
    print('Finished')

A 0\n1\nFinished

B 0\n1

C Finished

D 0\nFinished

💡 Hint

The else block runs only if the loop ends normally without break.

The loop runs twice printing 0 and 1, then else prints 'Finished'.

❓ Predict Output

advanced

While–else with continue and break

What is the output of this code?

Python

n = 0
while n < 4:
    n += 1
    if n == 2:
        continue
    if n == 3:
        break
    print(n)
else:
    print('Loop ended')

A 1\n4\nLoop ended

B 1

C 1\nLoop ended

D 2

💡 Hint

Check how continue skips printing and break stops the loop.

When n==2, continue skips print. When n==3, break stops loop before print. Only 1 is printed.

❓ Predict Output

advanced

While–else with nested loops and break

What does this code print?

Python

x = 0
while x < 3:
    y = 0
    while y < 3:
        if x == y:
            break
        print(f'{x},{y}')
        y += 1
    else:
        print('Inner done')
    x += 1
else:
    print('Outer done')

A Outer done

B 0,0\n1,0\n1,1\n2,0\n2,1\n2,2\nInner done\nOuter done

C 1,0\n2,0\n2,1\nOuter done

D 0,0\n1,0\n2,0\n2,1\nInner done\nOuter done

💡 Hint

Remember break exits the inner loop and else runs only if no break.

Inner loop breaks when x == y, so inner else never runs. Outer loop ends normally, so outer else runs.

🧠 Conceptual

expert

Understanding while–else behavior

Which statement about the while–else construct in Python is correct?

A The else block runs only if the while loop completes without encountering a break statement.

B The else block runs only if the while loop contains a continue statement.

C The else block runs every time after the while loop, regardless of break.

D The else block runs only if the while loop is skipped entirely.

💡 Hint

Think about when else runs in loops with break.

The else block runs only if the loop finishes normally without break.

Practice

1.

What happens to the else block in a while loop if the loop ends normally (without a break)?

easy

A. The else block runs before the loop starts.

B. The else block never runs.

C. The else block runs after the loop finishes all iterations.

D. The else block runs only if the loop has a break.

Solution

1. Step 1: Understand the while-else structure

   The else block after a while loop runs only if the loop finishes all iterations without encountering a break.

2. Step 2: Analyze loop ending conditions

   If the loop ends normally (condition becomes false), the else block executes. If a break occurs, it skips the else.

3. Final Answer:

   The else block runs after the loop finishes all iterations. -> Option C

4. Quick Check:

   while-else else runs if no break [OK]

Hint: Else runs only if while loop ends without break [OK]

Common Mistakes:

• Thinking else runs always after while
• Believing else runs only if break occurs
• Confusing else with finally block

2.

Which of the following is the correct syntax for a while loop with an else block in Python?

?

easy

A. while condition:
# code
else
# code

B. while condition:
else:
# code
# code

C. while condition:
# code
else:
# code

D. while condition:
# code
else:
# code

Solution

1. Step 1: Recall Python while-else syntax

   The else block must be aligned with the while, not indented inside it.

2. Step 2: Check each option's indentation and keywords

   while condition: # code else: # code correctly places else: aligned with while and indents code blocks properly.

3. Final Answer:

   while condition: # code else: # code -> Option D

4. Quick Check:

   Else aligned with while, colon included [OK]

Hint: Else must align with while, not inside loop body [OK]

Common Mistakes:

• Indenting else inside while block
• Missing colon after else
• Placing else before while

3.

What is the output of this code?

i = 0
while i < 3:
    print(i)
    i += 1
else:
    print('Done')

medium

A. 0
1
2

B. 0
1
2
Done

C. Done

D. 0
1
2
3
Done

Solution

1. Step 1: Trace the while loop iterations

   Variable i starts at 0 and increments by 1 each loop until i < 3 is false. It prints 0, 1, 2.

2. Step 2: Check else block execution

   Since the loop ends normally (i becomes 3, condition false), the else block runs and prints 'Done'.

3. Final Answer:

   0 1 2 Done -> Option B

4. Quick Check:

   Loop prints 0-2, else prints Done [OK]

Hint: Else runs after loop if no break, prints 'Done' [OK]

Common Mistakes:

• Ignoring else block output
• Expecting 3 to print inside loop
• Thinking else runs only on break

4.

Find the error in this code snippet:

i = 0
while i < 5:
    if i == 3:
        break
    print(i)
    i += 1
else:
print('Finished')

medium

A. The else block is not indented properly.

B. The break statement is outside the loop.

C. The while condition is invalid.

D. The print statement inside the loop is missing parentheses.

Solution

1. Step 1: Check indentation of else block

   The else block must be aligned with the while statement, but here it is not indented properly.

2. Step 2: Verify other parts

   Break is inside the loop, while condition is valid, and print uses parentheses correctly.

3. Final Answer:

   The else block is not indented properly. -> Option A

4. Quick Check:

   Else must align with while, indentation error [OK]

Hint: Else must align with while, check indentation [OK]

Common Mistakes:

• Misplacing else inside loop body
• Confusing break placement
• Ignoring indentation errors

5.

Consider this code:

n = 5
while n > 0:
    if n == 3:
        break
    print(n)
    n -= 1
else:
    print('Loop completed')

What will be the output and why?

hard

A. 5
4
Because break stops loop, else does not run.

B. 5
4
3
Loop completed
Because else always runs.

C. 5
4
3
Because break is inside if, else runs anyway.

D. Loop completed
Because else runs before loop.

Solution

1. Step 1: Trace loop iterations and break

   n starts at 5, prints 5 and 4. When n == 3, break stops the loop immediately.

2. Step 2: Understand else block behavior

   Because the loop was stopped by break, the else block does not run, so 'Loop completed' is not printed.

3. Final Answer:

   5 4 Because break stops loop, else does not run. -> Option A

4. Quick Check:

   Break skips else, so only 5 and 4 print [OK]

Hint: Break skips else; else runs only if no break [OK]

Common Mistakes:

• Assuming else runs even after break
• Printing 3 inside loop
• Thinking else runs before loop