8 2 Handling Multiple Exceptions Explained

Key Concepts

Handling multiple exceptions in Python involves several key concepts:

• Using multiple except blocks
• Handling multiple exceptions in a single except block
• Using else and finally blocks
• Raising custom exceptions

1. Using Multiple except Blocks

You can handle different types of exceptions by using multiple except blocks. Each except block can handle a specific type of exception.

Example:

try:
    num = int(input("Enter a number: "))
    result = 10 / num
except ValueError:
    print("Invalid input. Please enter a number.")
except ZeroDivisionError:
    print("Cannot divide by zero.")
    

Analogy: Think of multiple except blocks as having different specialists to handle different types of issues.

2. Handling Multiple Exceptions in a Single except Block

You can handle multiple exceptions in a single except block by specifying a tuple of exception types.

Example:

try:
    num = int(input("Enter a number: "))
    result = 10 / num
except (ValueError, ZeroDivisionError):
    print("An error occurred. Please enter a valid number.")
    

Analogy: Think of a single except block handling multiple exceptions as a generalist who can handle various issues.

3. Using else and finally Blocks

The else block is executed if no exceptions occur, and the finally block is always executed, regardless of whether an exception occurred.

Example:

try:
    num = int(input("Enter a number: "))
    result = 10 / num
except (ValueError, ZeroDivisionError):
    print("An error occurred. Please enter a valid number.")
else:
    print("The result is:", result)
finally:
    print("Execution completed.")
    

Analogy: Think of the else block as a celebration for a successful task, and the finally block as a cleanup step after the task is done.

4. Raising Custom Exceptions

You can raise custom exceptions to handle specific scenarios in your code. This allows for more precise error handling.

Example:

class CustomError(Exception):
    pass

try:
    num = int(input("Enter a number: "))
    if num < 0:
        raise CustomError("Negative numbers are not allowed.")
    result = 10 / num
except (ValueError, ZeroDivisionError):
    print("An error occurred. Please enter a valid number.")
except CustomError as ce:
    print(ce)
    

Analogy: Think of raising custom exceptions as creating a personalized error message for a specific situation.

Putting It All Together

By understanding and using these concepts effectively, you can handle multiple exceptions in Python, making your code more robust and user-friendly.

Example:

try:
    num = int(input("Enter a number: "))
    if num < 0:
        raise CustomError("Negative numbers are not allowed.")
    result = 10 / num
except (ValueError, ZeroDivisionError):
    print("An error occurred. Please enter a valid number.")
except CustomError as ce:
    print(ce)
else:
    print("The result is:", result)
finally:
    print("Execution completed.")