How to Write Clean Code: 5 Tips for a Maintainable Codebase

Writing clean code is an essential but often overlooked developer skill. Without it, a codebase can quickly become tough to maintain and even tougher to understand. Clean code makes it easier for others to read, review, and extend your work. Here are five tips from the Codility Engineering team to show you how to write clean, maintainable code and set you and your team up for the future.

Avoid Code Duplication by Writing Reusable Code

Code duplication leads to several problems:

• Fixing a bug or updating a feature requires modifying every duplicated instance separately.
• Developers waste time analyzing redundant code.
• Similar functionality may be reimplemented instead of being reused.

To prevent this, extract common logic into reusable components. For example, if two sections of code differ only slightly, consider refactoring them into a common function or class.

Design Before Implementing

A common mistake is jumping into implementation without proper planning. You write some code, then realize a class needs additional functionality. As a result, you add quick fixes or hacky lines. A few such lines later, your code becomes unreadable, or at best, poorly structured.

To avoid this, take time to design your solution first. Before you begin writing code, identify potential issues and edge cases. Then, structure your design to allow easy future expansion.

Use Meaningful Names

Imagine you’re writing a function to load data from a file. You quickly name it load without much thought. Later, you realize you also need to load data from a database, so you introduce another function called load2. Then, you have to add a function to load cached data, and now you’re staring at load3. That’s not ideal.

Generic names like load and load2 make your code confusing and hard to follow. It becomes impossible to understand what each function does without digging into the implementation. Instead, use names with clear, descriptive meanings like load_from_database. This improves readability and prevents misunderstandings as your codebase grows.

Keep Functions Short

When a function is too long, a number of issues arise:

• Tries to serve multiple distinct purposes.
• Becomes difficult to understand as a whole.
• Is harder to modify.
• Complicates unit testing since all functionalities must be tested together.

To address this, divide large functions into smaller, single-purpose functions. This makes your code easier to read, maintain, and test.

Use a Code Formatter

Common formatting issues include inconsistent spaces and indentation, or lines that are too long. To avoid these pitfalls, use a tool that will automatically format your code in a consistent way, like Black for Python or Clang-format for C++. Automatic formatting improves readability and allows you to focus on functionality rather than style issues. It also allows you to set a common formatting style with the team in an easy way.

Learning how to write clean code isn’t just about making your work presentable. It’s about creating a codebase that is readable, understandable, and maintainable by both your colleagues and your future self. These five tips will help you go from producing functional code to creating elegant solutions that stand the test of time.