python兑现Composite模式

python实现Composite模式
#-*-coding:utf-8-*-

'''
意图：将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示
'''
from abc import ABCMeta

class Component():
    __metaclass__ = ABCMeta
    def __init__(self):
        pass
    def operation(self):
        pass
    def add(self, com):
        if not isinstance(comp, Component):
            raise 'add method first argument shuld be a instance of Component!'
        
    def remove(self, comp):
        if not isinstance(comp, Component):
            raise 'remove method first argument shuld be a instance of Component!'
        
    def getChild(self, index):
        if not isinstance(index, int):
            raise 'getChild method first argument should be int type!'
    
class Composite(Component):
    compList = []
    def operation(self):
        for comp in tuple(self.compList):
            comp.operation()
            
    def add(self, comp):
        if not isinstance(comp, Component):
            raise 'add method first argument shuld be a instance of Component!'
        self.compList.append(comp)
        
    def remove(self, comp):
        if not isinstance(comp, Component):
            raise 'remove method first argument shuld be a instance of Component!'
        index = None
#        try:
#            index = self.compList.index(comp)
#        except:
#            raise "comp does't exists"
        #不用上面的,用index中的except机制，减少try使用耗时间
        index = self.compList.index(comp)
        if index is not None:
            del self.compList[index]
    def getChild(self, index):
        if not isinstance(index, int):
            raise 'getChild method first argument should be int type!'
        return self.compList[index]

class Leaf(Component):
    def operation(self):
        print 'Leaf operation...'


if __name__ == "__main__":
     leaf = Leaf()
     leaf.operation()
     
     composite = Composite()
     composite.add(leaf)
     composite.operation()
     
     leaf1 = composite.getChild(0)
     leaf1.operation()