Multiple exception handling in Python - Mini Project: Build & Apply

Multiple exception handling

📖 Scenario: You are writing a simple calculator program that takes two numbers and divides them. Sometimes, users might enter invalid input or try to divide by zero. You want to handle these errors gracefully.

🎯 Goal: Build a program that asks for two numbers, divides them, and uses multiple exception handling to catch ValueError and ZeroDivisionError.

📋 What You'll Learn

Create two variables num1 and num2 to store user input

Create a variable to store the division result

Use a try block to convert inputs to integers and perform the division

Use multiple except blocks to catch ValueError and ZeroDivisionError

Print the result if no error occurs

💡 Why This Matters

🌍 Real World

Handling errors is important in programs that take user input or perform calculations to avoid crashes and provide clear feedback.

💼 Career

Knowing how to manage multiple exceptions is a key skill for writing robust and user-friendly software.

1

Create variables for user input

Create two variables called num1 and num2. Assign input("Enter first number: ") to num1 and input("Enter second number: ") to num2.

Python

# Create variables num1 and num2 to store user inputs
# Your code here

Hint

Use input() to get user input as strings.

2

Create a variable for the result

Create a variable called result and set it to None.

Python

num1 = input("Enter first number: ")
num2 = input("Enter second number: ")
# Create a variable result and set it to None
# Your code here

Hint

Initialize result to None before using it.

3

Use try and multiple except blocks

Write a try block that converts num1 and num2 to integers using int(), divides them, and assigns it to result. Add two except blocks: one for ValueError that prints "Invalid input! Please enter numbers." and one for ZeroDivisionError that prints "Cannot divide by zero.".

Python

num1 = input("Enter first number: ")
num2 = input("Enter second number: ")
result = None
# Use try block to convert num1 and num2 to integers, divide and assign to result
# Add except blocks for ValueError and ZeroDivisionError
# Your code here

Hint

Put the integer conversions and division inside try. Use separate except blocks for each error type.

4

Print the result

Write a print statement that prints "Result: " followed by the value of result only if result is not None.

Python

num1 = input("Enter first number: ")
num2 = input("Enter second number: ")
result = None
try:
    num1 = int(num1)
    num2 = int(num2)
    result = num1 / num2
except ValueError:
    print("Invalid input! Please enter numbers.")
except ZeroDivisionError:
    print("Cannot divide by zero.")
# Print the result only if it is not None
# Your code here

Hint

Use if result is not None: before printing.

Practice

1.

What is the purpose of using multiple except blocks after a single try block in Python?

easy

A. To create multiple loops inside the try block

B. To run the same code multiple times

C. To handle different types of errors separately

D. To ignore all errors silently

Solution

1. Step 1: Understand the role of try-except

   The try block runs code that might cause errors, and except blocks catch those errors.

2. Step 2: Purpose of multiple except blocks

   Multiple except blocks allow catching different error types separately to handle each properly.

3. Final Answer:

   To handle different types of errors separately -> Option C

4. Quick Check:

   Multiple except blocks = handle different errors [OK]

Hint: Multiple except blocks catch different error types separately [OK]

Common Mistakes:

• Thinking multiple except blocks run all at once
• Believing except blocks create loops
• Assuming except blocks ignore errors

2.

Which of the following is the correct syntax to catch both ValueError and TypeError exceptions separately?

try:
    x = int(input())
except ???:
    print("Value error occurred")
except ???:
    print("Type error occurred")

easy

A. except ValueError:
except TypeError:

B. except (ValueError, TypeError):
except Exception:

C. except ValueError, TypeError:
except Exception:

D. except ValueError | TypeError:
except Exception:

Solution

1. Step 1: Check syntax for multiple except blocks

   Each except block must catch one exception type separately using except ExceptionType:.

2. Step 2: Identify correct syntax

   except ValueError: except TypeError: uses separate except blocks for ValueError and TypeError, which is correct syntax.

3. Final Answer:

   except ValueError: except TypeError: -> Option A

4. Quick Check:

   Separate except blocks = except ExceptionType: [OK]

Hint: Use separate except lines for each error type [OK]

Common Mistakes:

• Using commas or pipes inside except incorrectly
• Trying to catch multiple exceptions in one except without tuple
• Using wrong syntax like except ValueError, TypeError:

3.

What will be the output of the following code?

try:
    a = 5 / 0
except ValueError:
    print("Value Error")
except ZeroDivisionError:
    print("Zero Division Error")
else:
    print("No Error")
finally:
    print("Done")

medium

A. Zero Division Error
Done

B. Value Error
Done

C. No Error
Done

D. Zero Division Error

Solution

1. Step 1: Identify the error raised in try block

   The expression 5 / 0 raises a ZeroDivisionError.

2. Step 2: Match the except block and output

   The ZeroDivisionError except block runs, printing "Zero Division Error". The finally block always runs, printing "Done".

3. Final Answer:

   Zero Division Error Done -> Option A

4. Quick Check:

   ZeroDivisionError caught + finally runs = output A [OK]

Hint: Match error type to except block, finally always runs [OK]

Common Mistakes:

• Confusing ValueError with ZeroDivisionError
• Forgetting finally block always runs
• Expecting else block to run on error

4.

Find the error in this code snippet and choose the correct fix:

try:
    x = int('abc')
except ValueError, TypeError:
    print("Error occurred")

medium

A. Change except line to: except ValueError | TypeError:

B. Change except line to: except (ValueError, TypeError):

C. Change except line to: except ValueError, TypeError:

D. No change needed, code is correct

Solution

1. Step 1: Identify syntax error in except line

   The syntax except ValueError, TypeError: is invalid for catching multiple exceptions.

2. Step 2: Correct syntax for multiple exceptions

   Use a tuple of exceptions inside parentheses: except (ValueError, TypeError):.

3. Final Answer:

   Change except line to: except (ValueError, TypeError): -> Option B

4. Quick Check:

   Multiple exceptions need parentheses tuple [OK]

Hint: Use parentheses tuple for multiple exceptions in one except [OK]

Common Mistakes:

• Using commas without parentheses
• Using pipe | operator incorrectly
• Assuming original syntax is valid

5.

You want to write a function that tries to convert a string to an integer and then divide 100 by that number. It should handle ValueError if conversion fails, ZeroDivisionError if division by zero happens, and print "Success" if no error occurs, and print "Done" regardless of errors. Which code correctly implements this?

hard

A. def func(s):
try:
n = int(s)
result = 100 / n
except ValueError:
print("Conversion error")
except ZeroDivisionError:
print("Division by zero")
else:
print("Success")

B. def func(s):
try:
n = int(s)
result = 100 / n
except (ValueError, ZeroDivisionError):
print("Error")
finally:
print("Success")

C. def func(s):
try:
n = int(s)
result = 100 / n
except ValueError:
print("Conversion error")
except ZeroDivisionError:
print("Division by zero")
finally:
print("Success")

D. def func(s):
try:
n = int(s)
result = 100 / n
except ValueError:
print("Conversion error")
except ZeroDivisionError:
print("Division by zero")
else:
print("Success")
finally:
print("Done")

Solution

1. Step 1: Check handling of exceptions and success message

   Function must catch ValueError and ZeroDivisionError separately and print appropriate messages.

2. Step 2: Check use of else and finally blocks

   else runs only if no exception, so "Success" should be printed there. finally always runs, so "Done" can be printed there.

3. Step 3: Verify option correctness

   def func(s): try: n = int(s) result = 100 / n except ValueError: print("Conversion error") except ZeroDivisionError: print("Division by zero") else: print("Success") finally: print("Done") correctly uses separate except blocks, prints "Success" in else, and "Done" in finally.

4. Final Answer:

   Option D code correctly implements all requirements -> Option D

5. Quick Check:

   Separate except + else for success + finally for done [OK]

Hint: Use else for success, finally for cleanup, separate except blocks [OK]

Common Mistakes:

• Printing success in finally instead of else
• Combining exceptions in one except without separate messages
• Omitting finally block when needed