OOP interfaces

An interface defines the inputs and outputs of a thing.

Consider a kettle, for example: every kettle has an input for water, a button to start boiling the water, and an output for the same water. How exactly that gets implemented in a particular kettle is up to the kettle manufacturer.

This is different from Abstract Classes

For example, in the following code we are Creating a Python Interface with a Shape Abstract Class that serves as an OOP interfaces with the calculate_area method. and maintains good OOP Polymorphism

Note

This type of inheritance allows shapes to inherit interfaces rather than functionality.

# shapes_ocp.py
 
from abc import ABC, abstractmethod
from math import pi
 
class Shape(ABC):
    def __init__(self, shape_type):
        self.shape_type = shape_type
 
    @abstractmethod
    def calculate_area(self):
        pass
 
class Circle(Shape):
    def __init__(self, radius):
        super().__init__("circle")
        self.radius = radius
 
    def calculate_area(self):
        return pi * self.radius**2
 
class Rectangle(Shape):
    def __init__(self, width, height):
        super().__init__("rectangle")
        self.width = width
        self.height = height
 
    def calculate_area(self):
        return self.width * self.height
 
class Square(Shape):
    def __init__(self, side):
        super().__init__("square")
        self.side = side
 
    def calculate_area(self):
        return self.side**2