Custom Exceptions in Python

In Python, you can create your own custom exceptions by defining a new class that inherits from the Exception class. Custom exceptions are useful when you want to define your own error conditions that are specific to your application or module.

Here’s an example of how to define a custom exception in Python:

class CustomError(Exception):
    pass

In this example, we define a new class called CustomError that inherits from the Exception class. We don’t define any methods or attributes in this class, so it simply inherits the default behavior of the Exception class.

You can also define your own methods and attributes in your custom exception class, like this:

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

In this example, we define a new class called CustomError that has two attributes: message and code. We define a constructor method that takes two arguments, message and code, and uses the super() function to call the constructor of the parent Exception class. We then set the code attribute to the value of the code argument.

Here’s an example of how to use a custom exception in Python:

def process_data(data):
    if not data:
        raise CustomError("No data found", 404)
    # process the data here

try:
    process_data([])
except CustomError as e:
    print("Error:", e, "Error Code:", e.code)

In this example, we define a function called process_data that takes one argument, data. If data is empty, we raise a CustomError exception with a custom error message and an error code.

We then call the process_data function with an empty list as the argument. Since data is an empty list, the CustomError exception is raised and caught by the except block. We print the error message and the error code to the console.

Custom exceptions are useful when you want to define your own error conditions that are specific to your application or module. By defining your own custom exceptions, you can make your code more expressive and easier to understand, and provide more meaningful error messages to users.