5. Exception Handling best practices

Quiz: 0/5

The goal of this lesson is to help you write clean, efficient, and easy-to-maintain code when handling errors (exceptions). Instead of writing messy exception handling that hides problems, you'll learn best practices that make your code more readable and debuggable.

Avoiding bare except statements

Instead of catching all exceptions, specify the exact ones you expect.

Bad practice:

def divide(a, b):
    try:
        return a / b
    except:
        print("Something went wrong!")  # Too vague!

print(divide(10, 0))  # What went wrong? We don't know!

Better: Catch specific exceptions

def divide(a, b):
    try:
        return a / b
    except ZeroDivisionError:
        print("You can't divide by zero!")
    except TypeError:
        print("Both numbers must be of the correct type!")

print(divide(10, 2))  # Works fine
print(divide(10, 0))  # Handles division by zero properly
print(divide(10, "a"))  # Handles type error properly

Logging Exceptions

Logging helps us track errors without just printing them.

Bad practice:

def square(n):
    return n * n

print(square("hello"))  # TypeError, but no useful message

Better: Use logging

import logging

logging.basicConfig(level=logging.ERROR)  # Logs to console

def square(n):
    try:
        return n * n
    except TypeError as e:
        logging.error(f"Invalid operation: {e}")
        print("Error: Input must be a number!")

print(square(5))      # Works fine
print(square("hi"))   # Logs error and prints a message

Now, the error is logged and handled properly.

Using assert for debugging

Assertions help catch logic mistakes early.

Bad practice:

def calculate_speed(distance, time):
    return distance / time  # What if time is 0? Crash!

Better: Use assert to check conditions

def calculate_speed(distance, time):
    assert time > 0, "Time must be greater than zero!"
    return distance / time

print(calculate_speed(100, 5))  # Works fine
print(calculate_speed(100, 0))  # Triggers assertion error

• If time == 0, the program immediately stops and shows "Time must be greater than zero!".
• This is great for debugging because it prevents hidden bugs in the program.

Final thoughts

• Use specific exceptions (except ZeroDivisionError, not except:).
• Log errors properly (even if just in the console).
• Use assert for debugging, but remove it in production.