The Interface Segregation Principle (ISP) is a fundamental principle of object-oriented design that promotes the use of small, focused interfaces to increase code reusability and maintainability. In this blog, we will discuss the Interface Segregation Principle and provide an example in Python.

Understanding the Interface Segregation Principle

The Interface Segregation Principle is a part of the SOLID principles of object-oriented programming. It states that a client should not be forced to depend on interfaces it does not use. In other words, classes should be designed with small, focused interfaces that are tailored to the needs of their clients.

The Interface Segregation Principle can be summarized in the following statement: “Clients should not be forced to depend on interfaces they do not use.” This means that a class should only implement the methods that are relevant to its clients, and not implement methods that are not needed.

Example of the Interface Segregation Principle in Python

Let’s consider an example to understand the Interface Segregation Principle in Python. Suppose we have a class name Document that represents a document. The Document class has a method called print, which prints the document. We also have a class named Scanner that represents a scanner. The Scanner class has a method called scan, which scans a document.

Now, suppose we have a class named MultifunctionalDevice that represents a multifunctional device, which is capable of printing and scanning documents. We can implement the MultifunctionalDevice class by inheriting from both the Document and Scanner classes. However, this approach violates the Interface Segregation Principle since it forces clients of the MultifunctionalDevice class to depend on both print and scan methods, even if they only need one of them.

Here is an example of how we can implement the Document, Scanner, and MultifunctionalDevice classes in Python while adhering to the Interface Segregation Principle:

class Printable:
    def print(self):
        pass

class Scanner:
    def scan(self):
        pass

class Document(Printable):
    def print(self):
        print("Printing document...")

class MultifunctionalDevice(Printable, Scanner):

    def print(self):
        print("Printing document...")

    def scan(self):
        print("Scanning document...")

In this example, we have created two interfaces: Printable and Scanner. The Printable interface defines a print method, and the Scanner interface defines a scan method. We have also created a class named Document that implements the Printable interface and a class named MultifunctionalDevice that implements both the Printable and Scanner interfaces.

By using this approach, we can ensure that clients of the MultifunctionalDevice class are only forced to depend on the methods they need, and not on methods they do not need. This makes the code more flexible and maintainable.

Conclusion

In conclusion, the Interface Segregation Principle is a fundamental principle of object-oriented design that promotes code reusability and maintainability. By following this principle, we can create software systems that are easy to extend and maintain. In the example provided above, we demonstrated how to implement the Interface Segregation Principle in Python using a simple example. By following the Interface Segregation Principle, we can create software systems that are more flexible and maintainable.

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To read more about best practices:

• SOLID1 : Single Responsibility Principle in Python

• SOLID2 :Open-Closed Principle in Python

• SOLID3 :Liskov Substitution Principle in Python

• SOLID4 :Interface Segregation Principle in Python

• SOLID5 :Dependency Inversion Principle in Python

• SOLID in Flutter

• Best practices for API writing

• Code standards