How do you create and use Python’s custom exceptions?

Creating and Using Custom Exceptions in Python

Custom exceptions in Python allow you to define your own error types, providing more specific error handling for your applications. This guide will walk you through creating and using custom exceptions in Python, including best practices and examples.

Defining Custom Exceptions

• Inherit from the BaseException Class: Custom exceptions should inherit from the built-in Exception class or a subclass of it. This ensures that your custom exception integrates seamlessly with Python’s exception handling mechanisms.
• Initialize with Custom Attributes: You can add custom attributes to your exception class to provide additional context about the error. This can be done by overriding the __init__ method.

Example: Basic Custom Exception

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

Using Custom Exceptions

• Raise Custom Exceptions: Use the raise statement to throw your custom exceptions in your code when specific conditions are met.
• Catch Custom Exceptions: Handle custom exceptions using try and except blocks. This allows you to catch and respond to errors in a controlled manner.

Example: Handling Custom Exception

try:
    raise MyCustomError("This is a custom error message")
except MyCustomError as e:
    print(f"Caught an exception: {e.message}")

Best Practices

1. Be Descriptive: Name your custom exceptions clearly and provide meaningful error messages to help with debugging and error reporting.
2. Document Your Exceptions: Document your custom exceptions in your code to ensure that others understand their purpose and how to handle them properly.

By following these practices, you can effectively create and use custom exceptions in Python to enhance your error handling and make your code more robust and maintainable.