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      Interfaces

      Python Tutorial

      This Python tutorial has been written for the beginners to help them understand the basic to advanced concepts of Python Programming Language. After completing this tutorial, you will find yourself at a great level of expertise in Python, from where you can take yourself to the next levels to become a world class Software Engineer.

      Interfaces

      In software engineering, an interface is a software architectural pattern. An interface is like a class but its methods just have prototype signature definition without any body to implement. The recommended functionality needs to be implemented by a concrete class.
      In languages like Java, there is interface keyword which makes it easy to define an interface. Python doesn't have it or any similar keyword. Hence the same ABC class and @abstractmethod decorator is used as done in an abstract class.
      An abstract class and interface appear similar in Python. The only difference in two is that the abstract class may have some non-abstract methods, while all methods in interface must be abstract, and the implementing class must override all the abstract methods.

      Example

      from abc import ABC, abstractmethod
      class demoInterface(ABC):
         @abstractmethod
         def method1(self):
            print ("Abstract method1")
            return
      
         @abstractmethod
         def method2(self):
            print ("Abstract method1")
            return
      The above interface has two abstract methods. As in abstract class, we cannot instantiate an interface.
         obj = demoInterface()
               ^^^^^^^^^^^^^^^
      TypeError: Can't instantiate abstract class demoInterface with abstract methods method1, method2
      Let us provide a class that implements both the abstract methods. If doesn't contain implementations of all abstract methods, Python shows following error
         obj = concreteclass()
               ^^^^^^^^^^^^^^^
      TypeError: Can't instantiate abstract class concreteclass with abstract method method2
      The following class implements both methods
      class concreteclass(demoInterface):
         def method1(self):
            print ("This is method1")
            return
         
         def method2(self):
            print ("This is method2")
            return
            
      obj = concreteclass()
      obj.method1()
      obj.method2()

      Output

      When you execute this code, it will produce the following output
      This is method1
      This is method2