shape_is_abc.py

from abc import ABC, abstractmethod


class Shape(ABC):

    @abstractmethod
    def area(self):
        pass

    @abstractmethod
    def perimeter(self):
        pass


class Square(Shape):

    def __init__(self, side):
        self.side = side

    def area(self):
        return self.side ** 2


shape_obj = Shape()
square_obj = Square(5)

print(square_obj.area())