Custom Exceptions in Python 🎯

Welcome to our comprehensive guide on understanding and using Custom Exceptions in Python! This tutorial is designed for beginners and intermediate learners, providing a thorough yet easy-to-follow explanation of this powerful feature. Let's dive right in!

What are Exceptions in Python? 📝

Exceptions are errors or events that occur during the execution of a program. They can help us manage unexpected situations and make our code more robust.

By default, Python provides a variety of built-in exceptions like ZeroDivisionError, NameError, and TypeError. But sometimes, we might encounter situations where none of the built-in exceptions suit our needs. That's where Custom Exceptions come into play.

Creating Custom Exceptions 💡

Python allows us to create our own exceptions by defining a new class that inherits from the built-in Exception class. Let's create a custom exception for invalid user inputs:

python

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

    def __str__(self):
        return self.message

Now, we can raise our custom exception when required:

python

try:
    user_input = int(input("Enter an integer: "))
    if user_input < 0:
        raise InvalidInputError("Negative numbers are not allowed.")
except InvalidInputError as e:
    print(e)

In this example, we've created a custom exception InvalidInputError and used it to handle the case where the user enters a negative number.

Raising and Handling Multiple Exceptions 💡

You can raise multiple exceptions in Python by using multiple raise statements or by chaining them with commas. Here's an example:

python

class MyCustomException(Exception):
    def __init__(self, msg1, msg2):
        self.msg1 = msg1
        self.msg2 = msg2

    def __str__(self):
        return f"{self.msg1}\n{self.msg2}"

try:
    x = 1/0  # Raises a ZeroDivisionError
    raise MyCustomException("Custom Error 1", "Custom Error 2")
except ZeroDivisionError:
    print("Handling ZeroDivisionError")
except MyCustomException as e:
    print(e)

In this example, we've raised both a ZeroDivisionError and a custom exception MyCustomException. The code handles the ZeroDivisionError separately and catches the custom exception using a specific exception block.

Quiz 📝

By the end of this tutorial, you should have a good understanding of creating and handling custom exceptions in Python. Happy coding! 🎉