策略模式：

应用特性：接收任意对象，然后对不同的对象去做相同的一件事情。

结构特性：策略模式其实是利用了多态的特性，使用固定的方法，但是把对象作为个体抽离出来了，对象在这里有点象抽离出来的配置文件的意思

UML：

#!/usr/bin/env python
#encoding: utf-8

class baseclass:
    def __init__(self):  
        pass
    
    def dosomething(self):
        pass
    
class newclass1(baseclass):
    def __init__(self):
        pass
    
    def dosomething(self, perfix):
        print perfix + ':dosomething1'
        
class newclass2(baseclass):
    def __init__(self):
        pass
    
    def dosomething(self, perfix):
        print perfix + ':dosomething2'
        
class newclass3(baseclass):
    def __init__(self):
        pass
    
    def dosomething(self, perfix):
        print perfix + ':dosomething3'
          

class setclass:
    def __init__(self,something):
        if 'newclass1' == something:
            self.classobj = newclass1()
        elif 'newclass2' == something:
            self.classobj = newclass2()
        elif 'newclass3' == something:
            self.classobj = newclass3()
        else:
            return None
        
    def dosomething(self,perfix):
        self.classobj.dosomething(perfix)

        
if '__main__' == __name__:
    class1 = setclass('newclass1')
    class2 = setclass('newclass2')
    class3 = setclass('newclass3')
    print class1.__class__
    print class2.__class__
    print class3.__class__
    class1.dosomething('class1')
    class2.dosomething('class2')
    class3.dosomething('class3') 

结果：

__main__.setclass
__main__.setclass
__main__.setclass
class1:dosomething1
class2:dosomething2
class3:dosomething3