Why Clean Code Matters: An Overview of Best Practices for Writing Maintainable Programs

Let’s start this article with a story of what can happen if you do not write clean programming code:

One of the most famous examples of what can happen when you don’t write clean code is the case of the “Therac-25” radiation therapy machine. In the 1980s, the Therac-25 was a cutting-edge medical device designed to deliver radiation therapy to cancer patients. However, due to poor coding practices, it ended up causing a series of fatal overdoses.

The problem stemmed from a software bug that caused the machine to deliver excessive amounts of radiation to patients. In some cases, patients were exposed to radiation doses 100 times higher than what was intended. This led to severe injuries and even fatalities.

The cause of the bug was traced back to the way the software was designed. The Therac-25 used a hybrid software system that combined both software and hardware components. However, the software was poorly written, with inadequate error handling and no safeguards against certain types of errors. This made it possible for a race condition to occur, in which the machine’s software would enter an inconsistent state and deliver the wrong dose of radiation.

The result of this poor coding was a tragedy. Over the course of several years, at least six patients died and several others were severely injured. The manufacturer of the Therac-25 eventually faced lawsuits and regulatory sanctions, and the incident became a cautionary tale for the importance of writing clean and maintainable code in safety-critical systems.

This anecdote highlights the importance of following good coding practices and designing software with safety and maintainability in mind. By writing clean, well-structured code, developers can avoid the types of bugs and errors that can lead to disastrous consequences.

Clear and well-written code is essential for any programming project. It can make the difference between a codebase that is easy to maintain and extend, and one that is a nightmare to work with. To help you write clear and maintainable code, we have compiled a list of guidelines that you should follow.

1. Use Clear and Descriptive Variable and Function Names

Variable and function names should be clear, concise, and descriptive of their purpose. Avoid using ambiguous or generic names like ‘temp’, ‘data’, or ‘value’, as these can make it difficult to understand what your code is doing. Instead, use names that clearly describe the purpose of the variable or function, like ‘customerName’, ‘calculateTotal’, or ‘fetchDataFromAPI’.

def calculate_average_grade(student_grades):
    """
    This function calculates the average grade of a list of student grades.
    
    Args:
    student_grades (list of float): A list of student grades as float values.
    
    Returns:
    float: The average grade of the input list of student grades.
    """
    total_grade = 0.0  # Initialize a variable to store the total grade
    num_grades = len(student_grades)  # Get the number of grades in the list
    
    # Calculate the total grade by summing all the grades in the list
    for grade in student_grades:
        total_grade += grade
    
    # Calculate the average grade by dividing the total grade by the number of grades
    average_grade = total_grade / num_grades
    
    return average_grade

2. Write Short and Focused Functions

Functions should be small, focused, and do only one thing. This makes it easier to read, understand, and test your code. Aim for functions that are no longer than 10-20 lines, and have a clear input and output. If a function is doing too many things, consider breaking it down into smaller, more focused functions.

def add_numbers(a, b):
    """
    This function adds two numbers and returns the result.
    
    Args:
    a (int or float): The first number to be added.
    b (int or float): The second number to be added.
    
    Returns:
    int or float: The sum of the two input numbers.
    """
    return a + b

3. Write Good Documentation

Good documentation is essential for maintaining and extending your codebase. It should explain what your code does, why it does it, and how to use it. Use comments to explain the purpose and behavior of your code, and document your functions and classes using docstrings. Additionally, provide a README file that explains how to set up and run your project.

def fibonacci(n):
    """
    This function calculates the nth Fibonacci number using recursion.
    
    Args:
    n (int): The index of the Fibonacci number to be calculated.
    
    Returns:
    int: The value of the nth Fibonacci number.
    
    Raises:
    ValueError: If n is a negative integer.
    """
    # Check if n is a negative integer
    if n < 0:
        raise ValueError("n must be a non-negative integer.")
    
    # Base case
    if n == 0 or n == 1:
        return n
    
    # Recursive case
    return fibonacci(n-1) + fibonacci(n-2)

4. Be Consistent

Consistency is important for writing maintainable code. Follow consistent formatting, indentation, naming conventions, and coding style throughout your codebase. This makes it easier to read, understand, and modify your code. Use linting tools to enforce consistency automatically.

5. Encapsulate and Modularize Your Code

Encapsulation and modularization are techniques used to separate concerns and reduce coupling between different parts of your code. Encapsulate related functionality into classes and modules, and make sure that each class or module has a clear and well-defined purpose. This makes it easier to change and test your code without affecting other parts of the system.

class Calculator:
    """
    This class encapsulates the functionality of a simple calculator.
    """
    
    def add(self, num1, num2):
        """
        This method adds two numbers and returns the result.
        
        Args:
        num1 (int or float): The first number to be added.
        num2 (int or float): The second number to be added.
        
        Returns:
        int or float: The sum of the two input numbers.
        """
        return num1 + num2
    
    def subtract(self, num1, num2):
        """
        This method subtracts two numbers and returns the result.
        
        Args:
        num1 (int or float): The first number to be subtracted.
        num2 (int or float): The second number to be subtracted.
        
        Returns:
        int or float: The difference of the two input numbers.
        """
        return num1 - num2

6. Follow Sandi Metz’s Rules

Sandi Metz is a renowned software engineer who has developed a set of guidelines for writing maintainable code. Some of her key rules include:

• Classes should be smaller than 100 lines of code.
• Methods should be fewer than five lines of code.
• Pass no more than four parameters into a method.
• Controllers can instantiate only one object.
• Views can know only about one instance variable.
• Use only one dot per line (law of demeter).

Following these rules can help you write more maintainable and extensible code.

7. Follow the DRY Principle

The DRY (Don’t Repeat Yourself) principle is a fundamental principle of software engineering. It states that you should avoid duplicating code by using abstraction, inheritance, composition, or other techniques. If you find yourself writing the same code multiple times, consider refactoring it into a reusable function or class.

In conclusion, writing clear and maintainable code is essential for any programming project. By following these guidelines, you can ensure that your code is easy to read, understand, and modify. Remember, the goal of writing code is not just to make it work, but also to make it maintainable and extensible.