类属性;框架之信息分页

类属性：定义     @property
class Book(object):
    def __init__(self, name, author, state, bookIndex):
        self.name = name
        self.author = author
        # 0: 借出， 1：未借出
        self.__state = state
        self.bookIndex = bookIndex
    # @property： 定义一个类方法为私有属性的名称;让用户可以直接访问， 但不能任意修改;
    @property
    def state(self):
        return  self.__state
    # @属性名.seeter: 给属性赋值时先做判断; 当属性名=value会自动调用该函数;
    @state.setter
    def state(self, value):
        if value in [0,1]:
            self.__state = value
        else:
            raise  TypeError("状态只能是0或者1")
    #当del 属性名, 会自动调用该函数;
    @state.deleter
    def state(self):
        print "deleting....."

b = Book('python', 'a', 1, 'HX001')

print b.state
b.state = 0
print b.state
del b.state

```
1
0
deleting.....



框架之信息分页显示
页面显示信息很多时，一般都会分页显示，当用户选择N页时，显示改页的数据开始（start）和结束（end）

 hosts[0:10]  start= (1-1)*10  end=1*10
 hosts[10:20] start=(2-1)*10   end=2*20

hosts = ['172.25.254.' + str(i) for i in range(100)]

class Page(object):
    # current_page: 页数
    # per_items： 每页显示的元素数;
    def __init__(self, current_page=1, per_items=10):
        self.__current_page = current_page
        self.__per_items = per_items

    @property
    def start(self):
        val = (self.__current_page - 1) * self.__per_items
        return val

    @property
    def end(self):
        val = self.__current_page * self.__per_items
        return val

p = Page(3,5)
print hosts[p.start:p.end]


```
['172.25.254.10', '172.25.254.11', '172.25.254.12', '172.25.254.13', '172.25.254.14']