Error Handling

Introduction

Python uses exceptions to handle errors gracefully and prevent program crashes.

Try-Except Block

try:
    result = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero!")
except Exception as e:
    print(f"Error: {e}")
else:
    print("No errors occurred")
finally:
    print("This always runs")

Raising Exceptions

def validate_age(age):
    if age < 0:
        raise ValueError("Age cannot be negative")
    if age > 150:
        raise ValueError("Invalid age")
    return True

Custom Exceptions

class InvalidInputError(Exception):
    def __init__(self, message="Invalid input"):
        self.message = message
        super().__init__(self.message)

raise InvalidInputError("Input must be positive")

Common Exceptions

Practice Problems

1. Create a safe calculator that handles division by zero
2. Implement input validation with custom exceptions
3. Parse user input and handle all possible errors
4. Create a retry mechanism for failing operations
5. Build error logging system