python版本的组合模式

# -*- coding:UTF-8 -*-
import abc


class Component(metaclass=abc.ABCMeta):
    def __init__(self, name):
        self._name = name

    @abc.abstractmethod
    def add_component(self, c):
        pass

    @abc.abstractmethod
    def remove_component(self, c):
        pass

    @abc.abstractmethod
    def display(self, depth):
        pass


class Leaf(Component):
    def add_component(self, c):
        print("Can't add to a leaf")

    def remove_component(self, c):
        print("Can't remove from a leaf")

    def display(self, depth):
        print('-' * depth + self._name)


class Composite(Component):
    def __init__(self, name):
        super().__init__(name)
        self.children = []

    def add_component(self, c):
        self.children.append(c)

    def remove_component(self, c):
        self.children.remove(c)

    def display(self, depth):
        print('-' * depth + self._name)
        for component in self.children:
            component.display(depth + 2)


if __name__=='__main__':
    root=Composite("root")
    root.add_component(Leaf("leaf A"))
    root.add_component(Leaf("leaf B"))
    comp = Composite("Composite X")
    comp.add_component(Leaf("leaf XA"))
    comp.add_component(Leaf("leaf XB"))
    root.add_component(comp)
    comp2 = Composite('Composite XY')
    comp2.add_component(Leaf("leaf XYA"))
    comp2.add_component(Leaf("leaf XYB"))
    comp.add_component(comp2)
    root.add_component(Leaf('leaf C'))
    leaf=Leaf("leaf D")
    root.add_component(leaf)
    root.remove_component(leaf)
    root.display(1)