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Raising Custom Errors in Python

 


 

Raising Custom Errors in Python          show

Raising Custom Errors in Python

In Python, you can define your own exceptions by creating a new class that inherits from the built-in Exception class. This is useful when you need to create specific error types that can provide more information about what went wrong in your code.

1. Defining a Custom Exception

To define a custom exception, create a new class that inherits from Exception.


# Define a custom exception
class CustomError(Exception):
    pass

2. Raising a Custom Exception

Use the raise keyword to raise the custom exception.


# Raise a custom exception
raise CustomError("This is a custom error message")

3. Handling a Custom Exception

Use a try block to catch and handle the custom exception.


# Handle a custom exception
try:
    raise CustomError("This is a custom error message")
except CustomError as e:
    print(e)

# Output:
# This is a custom error message

4. Adding Attributes to Custom Exceptions

You can add attributes to your custom exceptions to provide additional information about the error.


# Custom exception with attributes
class CustomError(Exception):
    def __init__(self, message, code):
        self.message = message
        self.code = code
        super().__init__(message)

try:
    raise CustomError("An error occurred", 500)
except CustomError as e:
    print(e.message, "Error Code:", e.code)

# Output:
# An error occurred Error Code: 500

5. Using Custom Exceptions in Functions

Custom exceptions can be used in functions to signal specific error conditions.


# Function using custom exceptions
def check_positive(number):
    if number < 0:
        raise CustomError("Number must be positive", 400)
    return number

try:
    check_positive(-10)
except CustomError as e:
    print(e.message, "Error Code:", e.code)

# Output:
# Number must be positive Error Code: 400
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