Summary  
This chapter explains how to define and enforce formal interfaces in Python—using abstract base classes and protocols—for clearer, type-safe polymorphism by specifying required methods that implementing classes must provide.  

General domain of usage  
Plugin systems

**Interfaces and protocols** provide formal contracts that classes must implement, ensuring consistency across different objects. They bridge the gap between Python’s dynamic **duck typing** and more structured **polymorphism**, making codebases clearer, safer, and easier to extend.

Definition

**Abstract Base Classes (ABC)** and the **Protocol system** provide ways to define explicit interfaces that classes must follow. These mechanisms help ensure compatibility while preserving Python’s flexibility. By applying them in contexts such as shape hierarchies, drawable objects, or plugin systems, developers can design software that is both robust and maintainable, with clear behavioral contracts guiding implementation.

These mechanisms also strengthen **type safety** by verifying interface compliance early, improving IDE support, and catching violations before runtime. At the same time, they support common **design patterns**, enabling plugin architectures, dependency injection, easier testing, and modular design that is simpler to maintain and scale.

Which statement best highlights the difference between Abstract Base Classes (ABC) and Protocols?

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.

Explore how classes can share and extend functionality. You'll learn different inheritance patterns, from simple hierarchies to multiple inheritance and abstract classes, and see how they enable code reuse and scalability.

Discover how to build flexible systems by combining objects. Instead of relying only on inheritance, you'll see how composition lets you assemble behaviors in a modular, adaptable way.

Understand how different objects can share a common interface while behaving in their own way. This section shows how method overriding, interfaces, and protocols make your code more dynamic and reusable.

Learn how to safeguard internal data and control access to class attributes. You'll explore private attributes, getters and setters, and data-hiding techniques that keep your classes secure and maintainable.

Interfaces and Protocols

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Interfaces and Protocols