Python Custom Exceptions

Introduction

In this lab, we will dive into the world of Python custom exceptions using a fantasy kingdom scenario. The kingdom is under threat from a menacing dragon, and a brave dragon knight has been called upon to defend the kingdom. However, the knight encounters various challenges during this mission, emphasizing the need for customized exception handling in Python.

Custom Exception Creation

In this step, we will create a custom exception class to handle specific scenarios when the dragon knight faces obstacles.

1. Open a file named custom_exceptions.py in the /home/labex/project directory.

## custom_exceptions.py

## Custom exception class for handling dragon-related errors
class DragonError(Exception):
    def __init__(self, message):
        super().__init__(message + " - Beware of the dragon!")

After saving the file, you would now have custom exceptions ready to be used.

Using Custom Exception

Now, let's see how our dragon knight can utilize the custom exception to handle an encounter with the dragon.

1. Open a file named dragon_encounter.py in the /home/labex/project directory.

## dragon_encounter.py

from custom_exceptions import DragonError

def brave_encounter():
    try:
        ## Simulating an encounter with the dragon
        raise DragonError("Error in dragon's lair!")
    except DragonError as e:
        print(e)

brave_encounter()

Run the script:

python dragon_encounter.py

The information below should be displayed on your terminal:

Error in dragon's lair! - Beware of the dragon!

Summary

In this lab, we have designed a scenario involving a fantasy kingdom and a dragon knight to demonstrate the usage of custom exceptions in Python. By creating a custom exception class and using it in a simulated encounter with a dragon, you can understand the practical implementation of custom exceptions and their significance in handling specific error conditions.