Try–except execution flow in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to catch a division by zero error.

Python

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

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

AZeroDivisionError

BValueError

CTypeError

DIndexError

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong exception type like ValueError or TypeError.

Not catching the exception at all.

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

2fill in blank

medium

Complete the code to print a message when no error occurs.

Python

try:
    print("Hello")
except Exception:
    print("Error occurred")
else:
    [1]

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

Apass

Bprint("No errors!")

Craise

Dbreak

Attempts:

3 left

💡 Hint

Common Mistakes

Using raise inside else which re-raises an error.

Using break outside loops causing syntax error.

The else block runs only if no exception occurs. Printing a message here confirms no errors happened.

3fill in blank

hard

Fix the error in the except block to catch any exception.

Python

try:
    x = int('abc')
except [1]:
    print("Caught an error")

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

AException

BError

CBaseException

DValueError

Attempts:

3 left

💡 Hint

Common Mistakes

Using Error which is not a built-in exception class.

Using BaseException which is too broad and not recommended.

Exception is the base class for most errors and is commonly used to catch any error except system-exiting ones.

4fill in blank

hard

Fill both blanks to handle a file error and print a message.

Python

try:
    with open('file.txt', '[1]') as f:
        content = f.read()
except [2]:
    print("File not found")

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

Ar

Bw

CFileNotFoundError

DIOError

Attempts:

3 left

💡 Hint

Common Mistakes

Using write mode 'w' which creates the file instead of reading.

Catching IOError which is more general than FileNotFoundError.

Opening a file for reading uses mode 'r'. If the file does not exist, Python raises FileNotFoundError.

5fill in blank

hard

Fill all three blanks to handle multiple exceptions and print the error type.

Python

try:
    num = int(input('Enter a number: '))
    result = 10 / num
except [1]:
    print("Cannot convert input to integer")
except [2]:
    print("Division by zero error")
except [3]:
    print("Some other error occurred")

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

AValueError

BZeroDivisionError

CException

DTypeError

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up exception types and their purposes.

Not including a general exception handler.

ValueError handles invalid integer conversion, ZeroDivisionError handles division by zero, and Exception catches any other errors.

Practice

1. What is the main purpose of using a try-except block in Python?

easy

A. To speed up the program execution

B. To handle errors and prevent the program from crashing

C. To repeat a block of code multiple times

D. To define a new function

Solution

1. Step 1: Understand the role of try block

   The try block contains code that might cause an error during execution.

2. Step 2: Understand the role of except block

   The except block catches and handles the error so the program does not stop abruptly.

3. Final Answer:

   To handle errors and prevent the program from crashing -> Option B

4. Quick Check:

   Try-except handles errors = B [OK]

Hint: Try-except blocks catch errors to keep programs running [OK]

Common Mistakes:

• Thinking try-except speeds up code
• Confusing try-except with loops
• Using try-except to define functions

2. Which of the following is the correct syntax to catch a ZeroDivisionError in Python?

easy

A. try:
x = 1/0
except ZeroDivisionError:
print('Cannot divide by zero')

B. try:
x = 1/0
catch ZeroDivisionError:
print('Cannot divide by zero')

C. try:
x = 1/0
except:
print('Error')
finally ZeroDivisionError:

D. try:
x = 1/0
except ZeroDivisionError then:
print('Cannot divide by zero')

Solution

1. Step 1: Identify correct try-except syntax

   Python uses try: followed by except ExceptionType: to catch errors.

2. Step 2: Check each option for syntax errors

   try: x = 1/0 except ZeroDivisionError: print('Cannot divide by zero') uses correct except ZeroDivisionError: syntax; others use invalid keywords like catch or incorrect formatting.

3. Final Answer:

   try: x = 1/0 except ZeroDivisionError: print('Cannot divide by zero') -> Option A

4. Quick Check:

   Correct except syntax = A [OK]

Hint: Use 'except ExceptionType:' to catch specific errors [OK]

Common Mistakes:

• Using 'catch' instead of 'except'
• Adding 'then' after except
• Misplacing 'finally' keyword

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

try:
    print('Start')
    x = 5 / 0
    print('End')
except ZeroDivisionError:
    print('Error caught')
print('Done')

medium

A. Start
End
Error caught
Done

B. Error caught
Done

C. Start
Done

D. Start
Error caught
Done

Solution

1. Step 1: Trace code inside try block

   It prints 'Start', then tries to divide 5 by 0, which raises ZeroDivisionError before printing 'End'.

2. Step 2: Handle exception and continue

   The except block catches the error and prints 'Error caught'. After that, the program continues and prints 'Done'.

3. Final Answer:

   Start Error caught Done -> Option D

4. Quick Check:

   Exception stops try block, except runs = C [OK]

Hint: Error stops try; except runs; code after try-except runs [OK]

Common Mistakes:

• Assuming 'End' prints after error
• Missing that except block runs
• Thinking program stops after error

4. Identify the error in this code snippet:

try:
    print('Hello')
except ValueError
    print('Value error occurred')

medium

A. try block cannot have print statements

B. Missing parentheses after except

C. Missing colon ':' after except ValueError

D. except block must come before try block

Solution

1. Step 1: Check syntax of except statement

   The except line must end with a colon ':' to define the block.

2. Step 2: Identify missing colon

   In the code, except ValueError is missing the colon, causing a syntax error.

3. Final Answer:

   Missing colon ':' after except ValueError -> Option C

4. Quick Check:

   except line needs ':' = A [OK]

Hint: Always put ':' after except ExceptionType [OK]

Common Mistakes:

• Forgetting colon after except
• Adding parentheses after except
• Misordering try and except blocks

5. You want to safely convert user input to an integer, using try-except-else and catching ValueError specifically, printing 'Invalid input' for invalid input and 'Input is', num for valid input, without stopping the program. Which code does this?

hard

A. try:
num = int(input('Enter number: '))
except ValueError:
print('Invalid input')
else:
print('Input is', num)

B. try:
num = int(input('Enter number: '))
except:
print('Invalid input')
else:
print('Input is', num)

C. try:
num = int(input('Enter number: '))
except ValueError:
print('Invalid input')
finally:
print('Done')

D. try:
num = int(input('Enter number: '))
except ValueError:
print('Invalid input')

Solution

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

   The try block attempts conversion; except handles errors; else runs if no error occurs.

2. Step 2: Check which option prints 'Invalid input' on error and shows input if valid

   try: num = int(input('Enter number: ')) except ValueError: print('Invalid input') else: print('Input is', num) correctly prints 'Invalid input' on ValueError and prints the number if conversion succeeds.

3. Final Answer:

   try: num = int(input('Enter number: ')) except ValueError: print('Invalid input') else: print('Input is', num) -> Option A

4. Quick Check:

   Use except for errors, else for success = D [OK]

Hint: Use except for errors and else for success actions [OK]

Common Mistakes:

• Not using else to handle successful input
• Catching all exceptions without specifying
• Missing error handling causing crash