麦子学院——Python面向对象编程（P7深入类的属性）

题目

修改上节课的作业中定义的类：
1、使用属性包装器将私有属性__color包装为color（可读写）属性
2、运用描述符在Box类中创建一个类属性（盒子六面的图案字符，只能为数字1-6）
3、为其定义_call_()，当作为函数调用时，返回其体积。

答案

class Pattern:  #图案描述符
    def __init__(self, default=1):
        self.figure = default

    def __get__(self, instance, owner):
        return self.figure

    def __set__(self, instance, val):
        if val >= 1 and val <= 6:
            self.figure = val
        else:
             print("value is supposed to be within 1~6!")

    def __delete__(self, instance):
        pass


class Box:  # Box类

    pattern = Pattern() #图案
    instanceNum = 0  # 实例数

    def __init__(self, length=0, width=0, height=0, color=None):
        self.length = length  # 长
        self.width = width    # 宽
        self.height = height  # 高
        self.__volume = self.length * self.height * self.width  # 体积
        Box.instanceNum += 1
        self.__color = color  #颜色
        self.__disclosure = False   #打开标识符

    def __call__(self, *args, **kwargs):    #返回体积
        return self.__volume

    @property
    def color(self):
        return self.__color

    @color.setter
    def color(self, color):
        self.__color = color

    def open(self):
        if self.__disclosure == False:
            self.__disclosure = True
            print("the box has been opened!")
        else:
            print("repeated opening unpermitted!")

    def close(self):
        if self.__disclosure == True:
            self.__disclosure = False
            print("the box has been closed!")
        else:
            print("repeated closing unpermitted!")

测试

if __name__ == '__main__':
    a = Box(1, 2, 3, "red")
    print(a.color)  #red
    a.color="yellow"
    print(a.color)  #yellow
    print(a.pattern)    #1
    a.pattern = 3
    print(a.pattern)    #3
    a.pattern = 100 #value is supposed to be within 1~6!
    print(a())  #6