Try–except–else behavior in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of try-except-else with no exception

What is the output of this Python code?

Python

try:
    print("Start")
except ValueError:
    print("Error")
else:
    print("No Error")
print("End")

A Start\nNo Error\nEnd

B Start\nError\nNo Error\nEnd

C Start\nError\nEnd

D No Error\nEnd

💡 Hint

The else block runs only if no exception occurs in try.

Since no exception is raised, the try block prints 'Start', then else block prints 'No Error', and finally 'End' is printed.

❓ Predict Output

intermediate

Output when exception is caught in try-except-else

What is the output of this code?

Python

try:
    x = int('abc')
except ValueError:
    print('Caught ValueError')
else:
    print('No Error')
print('Done')

A No Error\nDone

B Caught ValueError\nDone

C Done

D Caught ValueError\nNo Error\nDone

💡 Hint

The else block does not run if an exception is caught.

The int conversion raises ValueError, so except block runs printing 'Caught ValueError'. The else block is skipped. Then 'Done' is printed.

❓ Predict Output

advanced

Behavior of try-except-else with finally

What is the output of this code snippet?

Python

try:
    print('Try block')
except Exception:
    print('Except block')
else:
    print('Else block')
finally:
    print('Finally block')

A Finally block

B Try block\nExcept block\nFinally block

C Try block\nFinally block

D Try block\nElse block\nFinally block

💡 Hint

Finally block always runs after try-except-else.

No exception occurs, so try prints 'Try block', else prints 'Else block', and finally prints 'Finally block'.

❓ Predict Output

advanced

Output when exception not caught by except

What happens when this code runs?

Python

try:
    print(10 / 0)
except ValueError:
    print('ValueError caught')
else:
    print('No Error')
print('After try-except')

A ZeroDivisionError is raised, program stops before printing 'After try-except'

B ValueError caught\nAfter try-except

C No Error\nAfter try-except

D After try-except

💡 Hint

Only ValueError is caught, ZeroDivisionError is not handled here.

ZeroDivisionError occurs but except only catches ValueError, so error propagates and program stops before last print.

🧠 Conceptual

expert

Understanding try-except-else-finally execution order

Consider this code:

try:
    print('A')
except Exception:
    print('B')
else:
    print('C')
finally:
    print('D')

What is the order of printed lines when no exception occurs?

A A, D, C

B A, B, C, D

C A, C, D

D D, A, C

💡 Hint

Else runs only if no exception, finally always runs last.

When no exception occurs, try prints 'A', else prints 'C', finally prints 'D'. So order is A, C, D.

Practice

1. What does the else block do in a try-except-else structure?

easy

A. Runs only if no error occurs in the try block

B. Runs only if an error occurs in the try block

C. Always runs regardless of errors

D. Runs before the try block

Solution

1. Step 1: Understand try-except-else flow

   The try block runs code that might cause an error. If an error happens, the except block runs.

2. Step 2: Role of else block

   The else block runs only if no error occurs in the try block, meaning the code succeeded without exceptions.

3. Final Answer:

   Runs only if no error occurs in the try block -> Option A

4. Quick Check:

   else runs if no error = A [OK]

Hint: Else runs only when try succeeds without errors [OK]

Common Mistakes:

• Thinking else runs after except
• Assuming else runs always
• Confusing else with finally

2. Which of the following is the correct syntax for a try-except-else block in Python?

easy

A. try:
pass
finally:
pass
else:
pass

B. try:
pass
else:
pass
except:
pass

C. try:
pass
except:
pass
else:
pass

D. except:
pass
try:
pass
else:
pass

Solution

1. Step 1: Recall correct order of blocks

   The correct order is try, then except, then else. The else block must come after except.

2. Step 2: Check each option

   try: pass except: pass else: pass follows the correct order and syntax. Options A, B, and D have wrong order or misplaced blocks.

3. Final Answer:

   try: pass except: pass else: pass -> Option C

4. Quick Check:

   try-except-else order = C [OK]

Hint: Remember order: try, except, else [OK]

Common Mistakes:

• Placing else before except
• Using else after finally
• Starting with except block

3. What will be the output of the following code?

try:
    print("Start")
    x = 1 / 1
except ZeroDivisionError:
    print("Error")
else:
    print("No Error")
print("End")

medium

A. Start\nNo Error\nEnd

B. Start\nEnd

C. Error\nNo Error\nEnd

D. Start\nError\nEnd

Solution

1. Step 1: Analyze try block execution

   The code prints "Start" and calculates 1/1 which is 1, no error occurs.

2. Step 2: Determine which blocks run

   Since no error, except block is skipped, else block runs printing "No Error", then "End" prints after.

3. Final Answer:

   Start No Error End -> Option A

4. Quick Check:

   No error means else runs = D [OK]

Hint: If no error, else runs after try [OK]

Common Mistakes:

• Thinking except runs without error
• Ignoring else block output
• Missing that print("End") always runs

4. Identify the error in this code snippet:

try:
    print(10 / 0)
else:
    print("No error")
except ZeroDivisionError:
    print("Error occurred")

medium

A. Syntax is correct

B. except block is missing

C. try block is empty

D. else block is before except block

Solution

1. Step 1: Check block order in try-except-else

   The correct order is try, except, then else. Here, else comes before except which is invalid syntax.

2. Step 2: Confirm syntax error

   Python raises a syntax error because else must follow except, not precede it.

3. Final Answer:

   else block is before except block -> Option D

4. Quick Check:

   else must come after except = A [OK]

Hint: Else must follow except, not before [OK]

Common Mistakes:

• Placing else before except
• Forgetting except block
• Misordering try-except-else blocks

5. Consider this code:

def check_value(val):
    try:
        result = 10 / val
    except ZeroDivisionError:
        return "Cannot divide by zero"
    else:
        return f"Result is {result}"

print(check_value(0))
print(check_value(5))

What is the output?

hard

A. Result is 0.0\nCannot divide by zero

B. Cannot divide by zero\nResult is 2.0

C. Cannot divide by zero\nResult is 0

D. Error at runtime

Solution

1. Step 1: Analyze call with 0

   When val=0, division causes ZeroDivisionError, so except block returns "Cannot divide by zero".

2. Step 2: Analyze call with 5

   When val=5, division succeeds (10/5=2.0), so else block returns "Result is 2.0".

3. Final Answer:

   Cannot divide by zero Result is 2.0 -> Option B

4. Quick Check:

   ZeroDivision triggers except, else runs if no error = B [OK]

Hint: Except returns on error; else returns on success [OK]

Common Mistakes:

• Assuming else runs even if error occurs
• Confusing output order
• Expecting runtime error instead of handled exception