DRY (Don’t Repeat Yourself)

This principle means you should not write the same code in many places. If you need to repeat something, create a function or class and reuse it. It helps make your code easier to update and understand.

KISS (Keep It Simple, Stupid)

Keep your code simple. Avoid complex solutions when a simple one works. Simple code is easier to read, test, and fix later.

YAGNI (You Ain’t Gonna Need It)

Don’t build features that you don’t need right now. Focus on what the project needs today, not what you might need in the future.

SOLID Principles

These are five rules that help you design better software:

  • S – Single Responsibility: Every class should have only one job.
  • O – Open/Closed: You can extend the class without changing it.
  • L – Liskov Substitution: Subclasses should work like their parent classes.
  • I – Interface Segregation: Don’t force classes to use things they don’t need.
  • D – Dependency Inversion: Depend on interfaces, not concrete classes.

These principles make code more flexible and easier to maintain.

Separation of Concerns

Each part of the program should handle one type of task. For example, one part manages the database, another part shows data to the user. This keeps your project organized.

Encapsulation

Hide the internal details of a class. Other parts of your code should use a simple interface to interact with it. This protects your data and avoids mistakes.

Abstraction

Show only what is necessary and hide complexity. For example, when you use a car, you don’t need to know how the engine works — you just drive.

Modularity

Break your program into small, independent modules. Each module does one thing and can be reused in other projects.

Loose Coupling

Make sure parts of your code don’t depend too much on each other. This way, you can change one part without breaking everything else.

High Cohesion

Each module or class should do one clear job and do it well. That makes your code cleaner and easier to understand.

Law of Demeter

A class should only talk to its close friends — not to the friends of friends. In simple words: keep communication short and direct.

Composition over Inheritance

Instead of creating many subclasses, use composition — build objects from smaller ones. It gives more flexibility and avoids problems with deep inheritance chains.

Convention over Configuration

Follow common naming and structure rules. If your framework has good defaults, use them instead of adding many custom settings.

Dependency Injection

Pass the objects your class needs from outside instead of creating them inside. This makes testing and replacing dependencies much easier.

Design Patterns

Design patterns are common solutions to typical programming problems. Examples include:

Singleton: Only one instance of a class. Factory: Creates objects without specifying the exact class. Observer: Notifies other parts when something changes. Strategy: Allows changing an algorithm’s behavior easily.

Test-Driven Development (TDD)

In TDD, you write tests before you write the code.

  • Write a test that fails.
  • Write the code to make it pass.
  • Refactor and improve your code.

This helps you write clean, reliable, and well-tested software.