For–else execution behavior in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this for–else code?

Consider the following Python code snippet. What will it print when executed?

Python

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

A

0
1
2
Done

B

0
1
2

C Done

D

0
1
Done

💡 Hint

The else block runs after the for loop completes normally without break.

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

Here, the loop prints 0, 1, 2 and then the else prints 'Done'.

❓ Predict Output

intermediate

What is the output when break is used inside for loop with else?

What will this code print when run?

Python

for i in range(5):
    if i == 2:
        break
    print(i)
else:
    print('Finished')

A

0
1
Finished

B

0
1
2
Finished

C

0
1

D

0
1
2

💡 Hint

The else block does not run if the loop is exited by break.

The loop breaks when i == 2, so it prints 0 and 1 only.

The else block is skipped because of the break.

🧠 Conceptual

advanced

When does the else block run in a for–else structure?

Choose the correct statement about the execution of the else block in a for–else loop.

A The else block runs only if the for loop has zero iterations.

B The else block runs only if the for loop contains a break statement.

C The else block runs after every iteration of the for loop.

D The else block runs only if the for loop completes all iterations without a break.

💡 Hint

Think about what happens when break is used inside the loop.

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

If break is used, else is skipped.

❓ Predict Output

advanced

What is the output of this nested for–else code?

Analyze the code below and select the output it produces.

Python

for x in range(2):
    for y in range(3):
        if y == 1:
            break
        print(f'{x},{y}')
    else:
        print('Inner else')
else:
    print('Outer else')

A

0,0
Inner else
1,0
Inner else
Outer else

B

0,0
1,0
Outer else

C

0,0
1,0
Inner else
Outer else

D

0,0
1,0

💡 Hint

Remember the else after inner loop runs only if inner loop completes without break.

The inner loop breaks when y == 1, so inner else is skipped both times.

The outer loop completes normally, so outer else runs.

❓ Predict Output

expert

How many items are in the dictionary after this for–else code runs?

What is the number of items in the dictionary d after executing this code?

Python

d = {}
for i in range(5):
    if i == 3:
        break
    d[i] = i * 2
else:
    d['done'] = True
print(len(d))

A 3

B 4

C 5

D 1

💡 Hint

Check if the else block runs when break is used.

The loop breaks when i == 3, so only keys 0,1,2 are added.

The else block is skipped, so 'done' key is not added.

Length is 3.

Practice

1.

What happens to the else block in a for-else statement if the loop completes all iterations without a break?

easy

A. The else block runs after the loop finishes.

B. The else block never runs.

C. The else block runs before the loop starts.

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

Solution

1. Step 1: Understand the for-else structure

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

2. Step 2: Apply to the question

   If the loop completes normally, the else block executes after the loop ends.

3. Final Answer:

   The else block runs after the loop finishes. -> Option A

4. Quick Check:

   For-else else runs if no break [OK]

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

Common Mistakes:

• Thinking else runs always
• Believing else runs before loop
• Confusing else with else-if

2.

Which of the following is the correct syntax for a for-else statement in Python?

___
    print(i)
else:
    print("Done")

easy

A. foreach i in range(3):

B. for i range(3):

C. for i in range(3):

D. for i to range(3):

Solution

1. Step 1: Recall correct for loop syntax

   Python uses for variable in iterable: syntax. So for i in range(3): is correct.

2. Step 2: Check options

   Only for i in range(3): matches correct syntax; others have syntax errors.

3. Final Answer:

   for i in range(3): -> Option C

4. Quick Check:

   Correct for loop syntax uses 'in' [OK]

Hint: Remember: for variable in iterable: [OK]

Common Mistakes:

• Omitting 'in' keyword
• Using 'to' instead of 'in'
• Using 'foreach' which is not Python

3.

What is the output of this code?

for num in [1, 2, 3]:
    if num == 4:
        break
else:
    print("No break encountered")

medium

A. No output

B. No break encountered

C. break

D. Error

Solution

1. Step 1: Analyze the loop and condition

   The loop checks if num == 4. Since 4 is not in the list, break never runs.

2. Step 2: Check the else block execution

   Because the loop completes without break, the else block runs and prints "No break encountered".

3. Final Answer:

   No break encountered -> Option B

4. Quick Check:

   Else runs if no break, so prints message [OK]

Hint: Else runs only if break never happens [OK]

Common Mistakes:

• Assuming else never runs
• Thinking break triggers else
• Expecting error due to missing break

4.

Find the error in this code snippet:

for i in range(3):
    if i == 1
        break
else:
    print("Loop ended")

medium

A. Missing colon after if condition

B. Missing colon after for loop

C. Indentation error in else block

D. break cannot be used inside for loop

Solution

1. Step 1: Check syntax of if statement

   The if statement is missing a colon at the end of the condition line.

2. Step 2: Verify other parts

   The for loop and else block have correct colons and indentation; break is valid inside loops.

3. Final Answer:

   Missing colon after if condition -> Option A

4. Quick Check:

   if statements require colon [:] [OK]

Hint: Check colons after if, for, else lines [OK]

Common Mistakes:

• Ignoring missing colon
• Thinking break is invalid
• Confusing indentation errors

5.

Consider this code:

def find_even(numbers):
    for n in numbers:
        if n % 2 == 0:
            print(f"Found even: {n}")
            break
    else:
        print("No even number found")

find_even([1, 3, 5])

What will be printed when calling find_even([1, 3, 5])?

hard

A. Found even: 3

B. Found even: 1

C. No output

D. No even number found

Solution

1. Step 1: Trace the loop with given list

   The list has only odd numbers: 1, 3, 5. None satisfy n % 2 == 0, so break never runs.

2. Step 2: Check else block execution

   Since no break occurred, the else block runs and prints "No even number found".

3. Final Answer:

   No even number found -> Option D

4. Quick Check:

   Else runs if no break, so prints no even found [OK]

Hint: Else runs only if no break in loop [OK]

Common Mistakes:

• Assuming else runs always
• Expecting break to run on odd numbers
• Ignoring else block behavior