策略模式

模式说明

定义算法家族并且分别封装，它们之间可以相互替换而不影响客户端。

模式结构图

程序示例

说明：选择不同排序算法

代码：

class OrderStrategy(object):
    """sort base"""
    def Sort(self,*args):
        pass

class Bubble(OrderStrategy):
    def Sort(self,args):
        args = list(args)
        length = len(args)
        for i in range(length):
            j = i + 1
            while j < length :
                if args[i] > args[j]:
                    args[i],args[j] = args[j],args[i]
                j = j + 1

        print "Bubble:" 
        print args
        return args

class Insertion(OrderStrategy):
    def Sort(self,args):
        args = list(args)
        length = len(args)
        for i in range(1,length):
            temp = args[i]
            #for j in range(i,-1,-1):#range don't contain the stop element so the middl -1 means stop at 0
            #    if args[j - 1] > temp and j>0:
            #        args[j] = args[j - 1]
            #    else:
            #        break
            j=i;
            while j>0:
                if args[j - 1] > temp:
                    args[j] = args[j - 1]
                    j=j-1;
                else:
                    break
            args[j] = temp #asignment the current (position i) element to j(the first element less than it on the left side of i)
        
        print "Insertion:"
        print args
        return args

class Selection(OrderStrategy):
    def Sort(self,args):
        #print args
        args = list(args)
        #print args
        length = len(args)
        smallValue = 0
        smallLocation = 0
        for i in range(0,length):
            #assume the smallest element and positon
            smallValue = args[i]
            smallLocation = i
            #find the truly smallest element and position
            for j in range(i + 1,length):
                if args[j] < smallValue:
                    smallValue = args[j]
                    smallLocation = j
            #exchange smallest element and current (position i) element
            args[i],args[smallLocation] = args[smallLocation],args[i]

        print "Selection:"
        print args
        return args

class SortHandler(object):
    strategy = OrderStrategy()
    def SetStrategy(self,strategy):
        self.strategy = strategy

    def sort(self,args):
        self.strategy.Sort(args)
        

sortList = (3,1,4,2,6)
if __name__ == '__main__':
    handler = SortHandler()
    handler.SetStrategy(Selection())
    handler.sort(sortList)
    handler.SetStrategy(Insertion())
    handler.sort(sortList)
    handler.SetStrategy(Bubble())
    handler.sort(sortList)

运行结果：

参考来源：

http://www.cnblogs.com/chenssy/p/3679190.html

http://www.cnblogs.com/wuyuegb2312/archive/2013/04/09/3008320.html

http://www.cnblogs.com/wangjq/archive/2012/07/03/2570344.html