What is custom exception classes in Python?

In Python, custom exception classes, also known as user-defined exceptions, are classes that you create to represent specific error conditions or exceptional situations in your code. While Python provides a wide range of built-in exception classes for common error types (e.g., ValueError, TypeError, FileNotFoundError), there are situations where you may need to define your own custom exceptions to handle application-specific errors or to provide more context and information about an exceptional condition.

Custom exception classes are typically derived from the base Exception class or one of its subclasses, such as BaseException, RuntimeError, or Exception. By creating your custom exception classes, you can add additional attributes, methods, and custom behavior to your exceptions to make them more informative and tailored to your application's needs.

Here's a basic example of how you might define a custom exception class in Python:

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

# Usage:
try:
    # Some code that may raise the custom exception
    raise CustomError("Custom error message", 500)
except CustomError as e:
    print(f"Custom error occurred: {e}")
    print(f"Error code: {e.code}")

In this example, we've defined a CustomError class that inherits from the base Exception class. This custom exception class takes a message and a code as arguments during initialization. When raising this custom exception, you can provide specific error messages and codes to help identify and handle different error scenarios.

Custom exception classes are particularly useful when you want to provide more context and detail about what went wrong in your code. They can also make error handling more organized and allow you to create exception hierarchies to handle different types of exceptions differently in your application. Apart from it by obtaining Python Online Training Course, you can advance your career in Python. With this course, you can demonstrate your expertise as an as Sequences and File Operations, Conditional statements, Functions, Loops, OOPs, Modules and Handling Exceptions, various libraries such as NumPy, Pandas, Matplotlib, many more.

By raising and catching custom exceptions, you can create robust error-handling mechanisms that improve the maintainability and readability of your code, as well as provide valuable information to developers and users when something unexpected happens.