Summary  
Composition is an object-oriented design technique that models has-a relationships by having classes contain instances of other classes to build flexible, modular systems, in contrast to inheritance’s is-a relationships.

General domain of usage  
Automotive (e.g., modeling a Car containing an Engine)

**Composition** represents a **has-a relationship**, where a class contains an instance of another class instead of inheriting from it. For example, a **Car has an Engine**. This differs from **inheritance**, which models an **'is-a' relationship**, such as a **Truck is a Vehicle**.

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`Car` does not inherit from `Engine`. Instead, it **contains** an `Engine` object and uses it to perform its work. This shows a **has-a** relationship, not **is-a**, making the design more flexible and easier to change later.

You should use composition when you need **flexible parts**, **clear boundaries**, and **runtime replacement** of behavior. **Prefer inheritance** when a **true is-a** hierarchy is obvious and stable.


Note

What is the main benefit of using composition?

Learn how to build clean, secure, and scalable applications with Object-Oriented Programming in Python. Cover the fundamentals of classes and objects, then moves into advanced concepts such as inheritance, composition, polymorphism, and encapsulation. With clear explanations and practical examples, you'll develop the ability to design Python programs that are powerful, maintainable, and ready for real-world use.

Learn the core building blocks of object-oriented programming in Python. This section covers classes, objects, methods, and variables, giving you a solid base to understand how OOP organizes and structures code.

Introduction to Composition