Beginner LevelPython
How do you create custom Exception classes in Python?
❓ Interview Prompt: Explain inheriting from `Exception` base class, custom error attributes, custom error messages, and exception hierarchies.
To create custom exceptions, define a new class that inherits from Python's built-in 'Exception' base class (or a specific subclass like 'ValueError'):
Best Practice:
•
Inherit from 'Exception' (NOT 'BaseException', which catches 'KeyboardInterrupt' and 'SystemExit'!).
•
Define custom domain exception hierarchies for clean error handling in SDKs and APIs.
Code Implementation Example
python
class InsufficientFundsError(Exception):
def __init__(self, balance, amount):
self.balance = balance
self.amount = amount
super().__init__(f'Cannot withdraw ${amount}. Current balance is ${balance}.')
# Usage:
def withdraw(balance, amount):
if amount > balance:
raise InsufficientFundsError(balance, amount)
return balance - amount💡Defining and raising custom domain exception classes.
🎯 Interview Key Takeaway
Inherit custom exceptions from Exception and attach domain metadata attributes to simplify error handling.
#Exceptions#Custom Exceptions#OOP#Beginner
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