174. Exception Hierarchy and Inheritance

Snippet 1: Viewing Python's Exception Hierarchy

import inspect

for cls in inspect.getmro(Exception):
    print(cls.__name__)

# Output:
# Exception
# BaseException
# object

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Snippet 2: Basic Try-Except with Built-in Exceptions

try:
    x = 10 / 0
except ZeroDivisionError as e:
    print(f"Caught an exception: {e}")

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Snippet 3: Catching Multiple Exceptions

try:
    x = int("abc")
except (ValueError, TypeError) as e:
    print(f"Caught an exception: {e}")

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Snippet 4: Raising a Built-in Exception

def divide(a, b):
    if b == 0:
        raise ZeroDivisionError("Division by zero is not allowed!")
    return a / b

try:
    divide(10, 0)
except ZeroDivisionError as e:
    print(f"Error: {e}")

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Snippet 5: Creating a Custom Exception

class CustomError(Exception):
    """Custom exception class for demonstration."""
    pass

try:
    raise CustomError("This is a custom error!")
except CustomError as e:
    print(f"Caught a custom exception: {e}")

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Snippet 6: Custom Exception with Additional Attributes

class ValidationError(Exception):
    def __init__(self, message, field):
        super().__init__(message)
        self.field = field

try:
    raise ValidationError("Invalid input", "username")
except ValidationError as e:
    print(f"Error: {e} (Field: {e.field})")

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Snippet 7: Using Inheritance for Custom Exceptions

class AppError(Exception):
    """Base class for application errors."""
    pass

class DatabaseError(AppError):
    """Raised for database-related errors."""
    pass

class NetworkError(AppError):
    """Raised for network-related errors."""
    pass

try:
    raise DatabaseError("Unable to connect to the database.")
except AppError as e:
    print(f"Application error: {e}")

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Snippet 8: Catching and Reraising Exceptions

try:
    try:
        x = int("abc")
    except ValueError as e:
        print(f"Caught an exception: {e}")
        raise
except Exception as e:
    print(f"Reraised exception: {e}")

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Snippet 9: Using __cause__ for Exception Chaining

try:
    try:
        raise ValueError("Invalid value")
    except ValueError as e:
        raise TypeError("Type mismatch") from e
except TypeError as e:
    print(f"Error: {e}")
    print(f"Caused by: {e.__cause__}")

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Snippet 10: Ensuring Cleanup with finally

try:
    x = 10 / 0
except ZeroDivisionError:
    print("Caught ZeroDivisionError")
finally:
    print("Cleanup code runs regardless of exceptions.")

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