Try–except–else behavior in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to catch a ZeroDivisionError exception.

Python

try:
    result = 10 / 0
except [1]:
    print("Cannot divide by zero")

Drag options to blanks, or click blank then click option'

AValueError

BIndexError

CZeroDivisionError

DTypeError

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong exception type like ValueError or TypeError.

Not catching any exception.

The ZeroDivisionError exception is raised when dividing by zero. Catching it allows the program to handle this error gracefully.

2fill in blank

medium

Complete the code to print 'Success' only if no exception occurs.

Python

try:
    x = 5 / 1
except ZeroDivisionError:
    print("Error")
else:
    print([1])

Drag options to blanks, or click blank then click option'

A"Failed"

B"Done"

C"Error"

D"Success"

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the success message inside except block.

Not using quotes around the string.

The else block runs only if the try block has no exceptions. So it prints "Success" here.

3fill in blank

hard

Fix the error in the code to correctly handle exceptions and print 'No error' if none occur.

Python

try:
    value = int('abc')
except ValueError:
    print("Conversion failed")
else:
    print([1])

Drag options to blanks, or click blank then click option'

A"No error"

BNo error

CNoError

Dno error

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the string in print.

Using undefined variable names.

The print statement needs a string in quotes. Without quotes, it causes a NameError.

4fill in blank

hard

Fill both blanks to create a try-except-else that prints the square root if no error occurs and prints 'Error' if a ValueError happens.

Python

import math

try:
    num = int(input('Enter a number: '))
    result = math.sqrt(num)
except [1]:
    print('Error')
else:
    print([2])

Drag options to blanks, or click blank then click option'

AValueError

BTypeError

Cresult

Dnum

Attempts:

3 left

💡 Hint

Common Mistakes

Catching the wrong exception type.

Printing the input number instead of the result.

The except block should catch ValueError from invalid int conversion. The else block prints the computed result.

5fill in blank

hard

Fill all three blanks to create a try-except-else that divides two numbers, catches ZeroDivisionError, and prints the quotient if no error.

Python

try:
    numerator = 10
    denominator = 2
    quotient = numerator [1] denominator
except [2]:
    print('Cannot divide by zero')
else:
    print([3])

Drag options to blanks, or click blank then click option'

A/

BZeroDivisionError

Cquotient

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using multiplication instead of division.

Catching the wrong exception.

Printing the wrong variable.

The division operator is /. The exception to catch is ZeroDivisionError. The else block prints the quotient.

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