Interface Segregation Principle

The principle of interface segregation states that a client should not be forced to implement an interface that it doesn't use. If an interface has methods that a client doesn't need, then it is considered "fat" or "unsegregated" and violates the principle of interface segregation.

Instead, the interface should be broken down into smaller, more specific interfaces, each of which defines a more narrowly focused set of methods. This allows clients to implement only the interfaces that they need, rather than being forced to implement a large, "fat" interface that defines a large number of methods that are not relevant to their needs.

Here's an example of a system that violates the interface segregation principle in Python:

In this example, the Superhero class defines three methods: fly, super_strength, and invisibility. However, not all superheroes have the ability to fly, use super strength, or become invisible. For example, Spiderman can swing from webs and use super strength, but he cannot fly or become invisible. This means that the Spiderman class is forced to implement the fly and invisibility methods of the Superhero class, even though it does not use them. This violates the principle of interface segregation, as it forces clients to depend on methods they do not use.

To fix this issue and make the system follow the interface segregation principle, we could create separate classes for each type of behavior:

In this revised version of the system, the Superman, Spiderman, Batman, and Ironman classes only implement the methods that are relevant to their abilities. This follows the principle of interface segregation, as it ensures that clients are not forced to depend on interfaces they do not use.