Clean Code: Definition and Principles - Part 3 (Last Part)

# Separate concepts vertically
class User:
    def __init__(self, name, email):
        self.name = name
        self.email = email

# Display closely related code vertically
class UserManager:
    def __init__(self):
        self.users = []

    def add_user(self, user):
        self.users.append(user)

# Define variables close to their usage
total_price = calculate_total_price(product_price, quantity)  # Good
# Avoid defining variables far from their usage
total_price = 0  # Bad

# Place related functions close to each other
def process_data(data):
    preprocess(data)
    analyze(data)

# Similar functions should be close to each other
def calculate_area_circle(radius):
    pass

def calculate_area_square(side_length):
    pass

# Functions should flow downwards
def step_one():
    pass

def step_two():
    pass

# Keep code lines short
result = perform_complex_calculation(data)  # Good
result = perform_a_very_complex_calculation_that_does_a_lot_of_things(data)  # Bad

# Avoid horizontal alignment (aligning with the line above or below)
first_name = "John"  # Good
last_name  = "Doe"   # Bad

# Use spacing to keep related things close, unrelated things distant
class User:
    def __init__(self, name, email):
        self.name = name
        self.email = email
    def print_details(self):
        print(f"Name: {self.name}, Email: {self.email}")

# Do not disrupt the indentation created by the code structure
if condition:
    do_something()
    do_another_thing()

# Hide the internal structure of the code
class Rectangle:
    def __init__(self, width, height):
        self.width = width
        self.height = height

# Prefer language-provided collection structures for data
user_list = []  # Good
user_dict = {}  # Good

# Avoid hybrid structures
# Use a clear and small structure
class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

# Work with a small number of variables
x, y, z = 1, 2, 3  # Good
coordinate1, coordinate2, coordinate3 = 1, 2, 3  # Bad

# Basic class should not know about its derived classes
class Animal:
    def make_sound(self):
        pass

# Favor having many simple functions over passing parameters to shape behavior
def calculate_area_circle(radius):
    pass

def calculate_area_square(side_length):
    pass

# Avoid static methods
class MathOperations:
    @staticmethod
    def add(a, b):
        return a + b  # Bad

# Use one assert per test
def test_calculate_total_price():
    assert calculate_total_price(10, 2) == 20

# Make tests readable
def test_user_manager_add_user():
    user_manager = UserManager()
    user_manager.add_user(User("John", "john@example.com"))
    assert len(user_manager.users) == 1

# Ensure tests run quickly
# Ensure tests are independent
# Ensure tests are repeatable