Custom Exceptions

Custom exceptions allow you to define your own error types to represent specific error conditions in your program. They help make error handling more precise and meaningful.

Creating Custom Exceptions

1. Define a Custom Exception Class: Inherit from the built-in Exception class or one of its subclasses.

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

2. Raise a Custom Exception: Use the raise keyword to trigger the custom exception in your code.

   def divide(x, y):
       if y == 0:
           raise MyCustomError("Cannot divide by zero.")
       return x / y
   
   try:
       result = divide(10, 0)
   except MyCustomError as e:
       print(f"Error: {e.message}")
   

Adding Additional Functionality

You can extend custom exceptions with additional attributes or methods to provide more context.

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

def process_data(data):
    if not data:
        raise DetailedError("No data provided.", 404)

try:
    process_data(None)
except DetailedError as e:
    print(f"Error: {e.message}, Code: {e.error_code}")

Best Practices

• Inherit from Exception: Ensure your custom exception inherits from Exception or a more specific built-in exception.
• Provide Meaningful Messages: Use descriptive messages to make the exception informative.
• Document Custom Exceptions: Clearly document when and why to use each custom exception.

Conclusion

Custom exceptions enhance error handling by allowing you to define and manage specific error conditions in a more controlled and descriptive manner. They provide better context for errors and make your codebase more maintainable.