Python structural patterns - composite

composite.py

# The composite pattern describes a group of objects that is treated the
# same way as a single instance of the same type of object.
from abc import ABC, abstractmethod


class Shape(ABC):
    @abstractmethod
    def draw(self):
        raise NotImplementedError


class Circle(Shape):
    def draw(self):
        print("Drawing a circle")


class Square(Shape):
    def draw(self):
        print("Drawing a square")


class Triangle(Shape):
    def draw(self):
        print("Drawing a triangle")


class Drawing(Shape):
    def __init__(self):
        self._shapes = []

    def add(self, shape):
        self._shapes.append(shape)

    def remove(self, shape):
        self._shapes.remove(shape)

    def draw(self):
        for shape in self._shapes:
            shape.draw()


drawing = Drawing()
for shape in [Circle(), Square(), Triangle()]:
    drawing.add(shape)

drawing.draw()
# Drawing a circle
# Drawing a square
# Drawing a triangle