Python-Design-Patterns composite

  1. composite Model
  2. Python-Design-Patterns composite

composite Model

Python-Design-Patterns composite

# file: ''
#!/usr/bin/env python
# -*- coding: utf-8 -*-

*What is this pattern about?
The composite pattern describes a group of objects that is treated the
same way as a single instance of the same type of object. The intent of
a composite is to "compose" objects into tree structures to represent
part-whole hierarchies. Implementing the composite pattern lets clients
treat individual objects and compositions uniformly.

*What does this example do?
The example implements a graphic class,which can be either an ellipse
or a composition of several graphics. Every graphic can be printed.

*Where is the pattern used practically?
In graphics editors a shape can be basic or complex. An example of a
simple shape is a line, where a complex shape is a rectangle which is
made of four line objects. Since shapes have many operations in common
such as rendering the shape to screen, and since shapes follow a
part-whole hierarchy, composite pattern can be used to enable the
program to deal with all shapes uniformly.


Describes a group of objects that is treated as a single instance.

class Graphic:
    def render(self):
        raise NotImplementedError("You should implement this.")

class CompositeGraphic(Graphic):
    def __init__(self): = []

    def render(self):
        for graphic in

    def add(self, graphic):

    def remove(self, graphic):

class Ellipse(Graphic):
    def __init__(self, name): = name

    def render(self):
        print("Ellipse: {}".format(

if __name__ == '__main__':
    ellipse1 = Ellipse("1")
    ellipse2 = Ellipse("2")
    ellipse3 = Ellipse("3")
    ellipse4 = Ellipse("4")

    graphic1 = CompositeGraphic()
    graphic2 = CompositeGraphic()


    graphic = CompositeGraphic()



### OUTPUT ###
# Ellipse: 1
# Ellipse: 2
# Ellipse: 3
# Ellipse: 4

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