Important Questions and Answers for Class 12 Computer Science Chapter 1 Exception Handling in Python | 2026-27

Exception Handling in Python explains how a program detects and responds to errors during execution. The following 15 important questions include MCQs, very short answers, short answers and long answers. They focus on both conceptual understanding and practical Python programming.

Class 12 Computer Science Chapter 1 MCQ with Answers

Q1. What will be the output of the following Python program?

try:

    a = 20

    b = 0

    print(a / b)

except ValueError:

    print("Invalid Value")

except ZeroDivisionError:

    print("Division by Zero")

finally:

    print("Program Completed")

(a) Invalid Value
(b) Division by Zero
(c) Division by Zero followed by Program Completed
(d) Program Completed only

Answer: (c) Division by Zero followed by Program Completed

Explanation: Dividing 20 by zero raises a ZeroDivisionError. The corresponding except block executes, followed by the finally block.

Output:

Division by Zero

Program Completed

Q2. Consider the following Python code. What will happen when it is executed?

numbers = [10, 20, 30]

try:

    print(numbers[5])

except IndexError:

    print("Invalid Index")

else:

    print("Access Successful")

(a) 30
(b) Invalid Index
(c) Access Successful
(d) Both Invalid Index and Access Successful

Answer: (b) Invalid Index

Explanation: The list contains three elements at indices 0, 1 and 2. Accessing index 5 raises an IndexError. The except block executes, while the else block is skipped.

Q3. What will be the output of the following code?

try:

    value = int("12.5")

    print(value)

except ValueError:

    print("Conversion Failed")

finally:

    print("End")

(a) 12.5
(b) 12
(c) Conversion Failed followed by End
(d) End only

Answer: (c) Conversion Failed followed by End

Explanation: The string "12.5" cannot be directly converted into an integer using int(). Python raises a ValueError, so the exception handler executes. The finally block also runs.

Output:

Conversion Failed

End

Q4. Identify the correct output of the following Python program.

try:

    x = 15

    assert x % 2 == 0, "Odd Number"

    print("Even Number")

except AssertionError as e:

    print(e)

(a) Even Number
(b) Odd Number
(c) AssertionError
(d) No output

Answer: (b) Odd Number

Explanation: The condition 15 % 2 == 0 is false. Therefore, assert raises an AssertionError with the message "Odd Number". The except block catches the exception and prints the message.

Class 12 Computer Science Chapter 1 Very Short Answer Questions

Q5. What is an exception in Python? Give two examples.

Answer: An exception is an error-related object that Python raises when an exceptional situation occurs during program execution. An unhandled exception can interrupt a program's normal execution.

Examples:

• ZeroDivisionError: Raised when a number is divided by zero.

• IndexError: Raised when a sequence index is outside the valid range.

Q6. Differentiate between throwing and catching an exception in Python.

Answer:

• Throwing an exception: Raising an exception when an error occurs or when the programmer explicitly uses raise.

• Catching an exception: The process of handling a raised exception using a suitable exception handler.

For example, when a program attempts division by zero, Python raises ZeroDivisionError. An except ZeroDivisionError block can catch and handle it.

Q7. What is the purpose of the else and finally clauses in exception handling?

Answer:

• else: Executes when the try block completes without raising an exception.

• finally: Executes when control leaves the try statement, whether an exception occurred or not. It is commonly used for cleanup operations.

Class 12 Computer Science Chapter 1 Short Answer Questions

Q8. Justify the statement: "Every syntax error is an exception, but every exception is not a syntax error."

Answer: Python represents syntax errors using exception classes such as SyntaxError. However, exceptions can also occur when a syntactically correct program performs an invalid operation during execution.

For example:

Syntax error:

if 10 > 5  
print("True")

This code raises SyntaxError because the colon (:) is missing after the if condition.

Runtime exception:

a = 10
b = 0
print(a / b)

This program has valid syntax but raises ZeroDivisionError during execution.

Therefore, syntax errors form one category of Python exceptions, but exceptions are not limited to syntax errors.

Q9. Identify the exceptions raised by the following Python statements and explain their causes.

(a) print(25 / 0) 

(b) print(int("Python")) 

(c) print(data) when data has not been defined 

(d) print([5, 10, 15][4]) (e) print("Age:" + 18)

Answer:

Explanation: Understanding the causes of built-in exceptions helps students identify programming mistakes and select appropriate exception handlers.

Q10. Complete the following Python program by filling in the missing keywords and exception names.

print("Learning Exceptions")

try:

    num1 = int(input("Enter first number: "))

    num2 = int(input("Enter second number: "))

    result = num1 / num2

except __________:

    print("Enter valid integers")

except __________:

    print("Denominator cannot be zero")

else:

    print("Result:", result)

__________:

    print("Program Finished")

Answer:

The missing entries, in order, are:

1. ValueError

2. ZeroDivisionError

3. finally

Completed Program:

print("Learning Exceptions")

try:

    num1 = int(input("Enter first number: "))

    num2 = int(input("Enter second number: "))

    result = num1 / num2

except ValueError:

    print("Enter valid integers")

except ZeroDivisionError:

    print("Denominator cannot be zero")

else:

    print("Result:", result)

finally:

    print("Program Finished")

Explanation:

• ValueError handles invalid integer input.

• ZeroDivisionError handles division by zero.

• else displays the result when no exception occurs.

• finally displays "Program Finished" after the operation or exception handling.

Q11. Predict the output of the following Python program for each input: (i) 5, (ii) 0 and (iii) abc.

try:

    x = int(input("Enter a number: "))

    result = 20 / x

except ValueError:

    print("Invalid Input")

except ZeroDivisionError:

    print("Cannot Divide")

else:

    print("Result:", result)

finally:

    print("Execution Complete")

Answer:

Case (i): Input = 5

Result: 4.0

Execution Complete

Since 20 divided by 5 is 4.0, no exception occurs. The else and finally blocks execute.

Case (ii): Input = 0

Cannot Divide

Execution Complete

Division by zero raises ZeroDivisionError. Its matching exception handler executes, followed by finally.

Case (iii): Input = abc

Invalid Input

Execution Complete

The input "abc" cannot be converted into an integer, so ValueError is raised. The corresponding handler executes, followed by finally.

Key Learning: This question tests input conversion, exception identification and the execution order of try, except, else and finally.

Class 12 Computer Science Chapter 1 Long Answer Questions

Q12. Explain the exception-handling process in Python with a suitable program and flowchart.

Answer: Exception handling is the process of identifying and managing errors that may occur while a Python program is running. It helps a program respond to unexpected situations without terminating abruptly.

The exception-handling process involves the following steps:

1. Exception occurs: An invalid operation occurs during program execution.

2. Exception is raised: Python creates an exception object containing information about the error.

3. Handler is searched: Python looks for an appropriate exception handler.

4. Exception is caught: If Python finds a matching handler, it executes its code.

5. Exception propagates: If no matching handler is available in the current context, Python searches through the calling contexts.

6. Program termination: If the exception remains unhandled, normal execution stops, and Python displays a traceback.

Flowchart of Exception Handling in Python

Example Program:

try:

    a = 50

    b = int(input("Enter denominator: "))

    result = a / b

    print("Result:", result)

except ZeroDivisionError:

    print("Cannot divide by zero")

except ValueError:

    print("Enter a valid integer")

Explanation: The program attempts to divide 50 by the user's input. If the denominator is zero, it handles ZeroDivisionError. If the input cannot be converted into an integer, it handles ValueError. Otherwise, it prints the quotient.

Q13. Write a Python program that accepts two numbers and displays their quotient. Use both raise and assert statements to check for a zero denominator.

Answer: Both raise and assert can trigger exceptions, but they serve different purposes.

Part A: Program using raise

try:

    numerator = int(input("Enter numerator: "))

    denominator = int(input("Enter denominator: "))

    if denominator == 0:

        raise ZeroDivisionError("Denominator cannot be zero")

    quotient = numerator/denominator

    print("Quotient:", quotient)

except ZeroDivisionError as e:

    print(e)

except ValueError:

    print("Enter valid integers")

Sample Input:

Enter numerator: 50

Enter denominator: 0

Output:

Denominator cannot be zero

Explanation:

• The program accepts two integers.

• The if condition checks whether the denominator is zero.

• If it is zero, raise explicitly triggers ZeroDivisionError.

• The exception handler catches the error and prints the message.

• Otherwise, it calculates and displays the quotient.

Part B: Program using assert

try:

    numerator = int(input("Enter numerator: "))

    denominator = int(input("Enter denominator: "))

    assert denominator != 0, "Denominator cannot be zero"

    quotient = numerator/denominator

    print("Quotient:", quotient)

except AssertionError as e:

    print(e)

except ValueError:

    print("Enter valid integers")

Sample Input:

Enter numerator: 50

Enter denominator: 0

Output:

Denominator cannot be zero

Explanation:

The assert statement checks whether the denominator is non-zero. When the condition is false, Python raises an AssertionError with the specified message. The matching except block catches the exception.

Difference Between raise and assert

Note: Assertions may be disabled when Python runs in optimised mode. The raise statement is preferable for essential input validation.

Q14. Write a Python program that handles multiple exceptions using try, except, else and finally. Explain the output for different inputs.

Answer:

try:

    num1 = int(input("Enter first number: "))

    num2 = int(input("Enter second number: "))

    result = num1 / num2

except ValueError:

    print("Invalid Input")

except ZeroDivisionError:

    print("Division by zero is not allowed")

else:

    print("Quotient:", result)

finally:

    print("Program Execution Completed")

Case 1: Valid Inputs

Input:

Enter first number: 20

Enter second number: 5

Output:

Quotient: 4.0

Program Execution Completed

Both inputs are valid, and no exception occurs. The else block displays the quotient, followed by the finally block.

Case 2: Zero Denominator

Input:

Enter first number: 20

Enter second number: 0

Output:

Division by zero is not allowed

Program Execution Completed

The ZeroDivisionError handler executes, and the else block is skipped.

Case 3: Invalid Input

Input:

Enter first number: abc

Output:

Invalid Input

Program Execution Completed

The first input cannot be converted to an integer, so Python raises a ValueError before it requests the second number.

Conclusion: Multiple except blocks allow the programmer to respond to different errors separately. The else block runs only when the try block completes successfully, while the finally block runs regardless of whether an exception occurs.

Q15. Study the following Python program and predict its output. Explain what happens when an exception is not handled by any except block.

try:

    x = int(input("Enter a number: "))

    y = 10 / x

except ZeroDivisionError:

    print("Division Error")

else:

    print("Result:", y)

finally:

    print("Finally Executed")

print("End of Program")

Predict the output when the user enters:

(a) 2
(b) 0
(c) abc

Answer:

Case (a): Input = 2

Result: 5.0

Finally Executed

End of Program

Explanation: The division completes successfully. The else block executes, followed by finally. The last print statement also executes.

Case (b): Input = 0

Division Error

Finally Executed

End of Program

Explanation: Division by zero raises ZeroDivisionError. The matching handler catches it. After executing finally, the program continues to its last statement.

Case (c): Input = abc

Finally Executed

After this line, Python displays a traceback ending with a ValueError message because "abc" cannot be converted into an integer.

Explanation:

1. The int() conversion raises a ValueError.

2. The program contains only a handler for ZeroDivisionError.

3. Since no handler matches ValueError, it remains unhandled.

4. The finally block executes before the exception propagates.

5. The final statement print("End of Program") is not executed.

Key Learning: A finally block can execute even when an exception remains unhandled. However, it does not automatically catch or suppress that exception.

Key Topics to Focus on in Class 12 Computer Science Chapter 1 - Vedantu's Expert Guide

Vedantu's Class 12 Computer Science Chapter 1 Important Questions cover key exception-handling concepts in Python. Students should focus on common errors, exception handling, and predicting the output of Python programs.

How to Prepare Class 12 Computer Science Chapter 1 Important Questions for CBSE Exams?

Vedantu recommends focusing on practical Python questions rather than memorising definitions alone.

• Predict program outputs: Trace code line by line to understand how it executes.

• Practise error identification: Find incorrect statements and identify the exceptions they raise.

• Complete Python programs: Solve missing-code questions involving exception handlers.

• Test different inputs: Run programs with valid, zero and invalid values to understand their behaviour.

Students can use the Class 12 Computer Science Chapter 1 Important Questions PDF download option for offline revision. Regular coding practice helps build confidence in solving exception-handling questions.

Important Study Material Links for Class 12 Computer Science Chapter 1

Students can strengthen their understanding of Exception Handling in Python using these chapter-specific learning resources.

Class 12 Computer Science Chapter-Wise Important Questions

Additional Study Materials for Class 12 Computer Science