Topic Overview

Welcome to the world of refactoring! We're learning about Code Smells, which are patterns in code that hint at potential problems. Our mission is to help you spot these smells and understand how to improve them or, in programming terms, how to 'refactor' them. We'll delve into the concept of 'code smells', examine different types, and apply real-world code examples to solidify your understanding. Let's get started!

Introduction to Code Smells

Code smells are signs that something could be amiss in our code. You could compare them to an unpleasant smell in a room. But instead of indicating rotten food or a dirty sock, they signal that our code may not be as readable, efficient, or manageable as it could be.

Consider this bit of code:

def calculate(quantity, price):
    return quantity * price

total = calculate(5, 3)

The function name calculate is too vague. What exactly does it calculate? For whom? This ambiguity is a sign of a 'bad naming' code smell.

Duplicate Code

If you notice the same piece of code in more than one place, you may be looking at an example of the 'Duplicate Code' smell. Duplicate code leaves room for errors and bugs. If you need to make a change, you might overlook one instance of duplication.

Here's an example:

total_apples_price = quantity_apples * price_apple - 5
total_bananas_price = quantity_bananas * price_banana - 5

This code performs the same operation on different data. Instead of duplicating the operation, we can create a function to handle it:

def calculate_price(quantity, price):
    discount = 5
    return quantity * price - discount

total_apples_price = calculate_price(quantity_apples, price_apple)
total_bananas_price = calculate_price(quantity_bananas, price_banana)

With this solution, if we need to change the discount or the formula, we can do so in one place: the calculate_price function.

Too Long Method

A method that does too many things or is too long is harder to read and understand, making it a prime candidate for the 'Too Long Method' smell.

Consider this example:

def process_order(order):
    print("Processing order...")
    if order.is_valid():
        print("Order is valid")
        if order.payment_type == "credit_card":
            process_credit_card_payment(order)
            send_order_confirmation_email(order)
        elif order.payment_type == "paypal":
            process_paypal_payment(order)
            send_order_confirmation_email(order)
        elif order.payment_type == "bank_transfer":
            process_bank_transfer_payment(order)
            send_order_confirmation_email(order)
        else:
            print("Unsupported payment type")
            return False
        print("Order processed successfully!")
        return True
    else:
        print("Invalid order")
        return False

This function handles too many aspects of order processing, suggesting a 'Too Long Method' smell. A better approach could involve breaking down the functionality into smaller, more focused methods.

For example, the updated code can look like this:

def process_payment(payment_type, order):
    if payment_type == "credit_card":
        process_credit_card_payment(order)
    elif payment_type == "paypal":
        process_paypal_payment(order)
    elif payment_type == "bank_transfer":
        process_bank_transfer_payment(order)
    else:
        print("Unsupported payment type")
        return False
    return True

def process_order(order):
    print("Processing order...")
    if not order.is_valid():
        print("Invalid order")
        return False
    
    if process_payment(order.payment_type, order):
        send_order_confirmation_email(order)
        print("Order processed successfully!")
        return True
    else:
        return False
Sign up
Join the 1M+ learners on CodeSignal
Be a part of our community of 1M+ users who develop and demonstrate their skills on CodeSignal