python之路--面向对象之封装

class Person:
    def __init__(self,height,weight,name,sex):
        self.__height = height            # 私有属性：外部不能调用
        self.weight = weight
        self.name = name
        self.sex = sex

    def tell_bmi(self):
        return self.weight / self.__height ** 2
    def tell_height(self):      # 建议这样查看值，用户不可以直接修改
        return self.__height

    def set_height(self,new_height):        # 建议这样修改值，即安全又人性化
        self.__height = new_height if new_height > 20 else self.__height
        return self.__height            # return不能返回赋值语句


dennis = Person(1.75,120,‘dennis‘,‘man‘)
print(dennis.tell_bmi())
print(dennis.__dict__)
print(dennis._Person__height)
print(dennis.tell_height())
print(dennis.set_height(-123))      # 设置不成功

# 私有属性：
# 在本类中就可以正常使用
# 在本类外就必须_类名__属性名调用（不建议使用）

class Goods:
    __price = 3         ### 私有公共属性
    def __init__(self,name,num):
        self.name = name
        self.num = num
    def goods_price(self):
        return self.num * Goods.__price

banana = Goods(‘egon‘,2)
print(banana.goods_price())
print(Goods.__dict__)
print(Goods._Goods__price)

class Foo:
    def __init__(self,height,weight):
        self.height = height
        self.weight = weight

    def tell_bmi(self):
        return self.weight / self.__height_pow()
    def __height_pow(self): # 私有方法
        return self.height ** 2


dennis = Foo(1.7,125)
print(dennis.tell_bmi())
print(dennis._Foo__height_pow())    # 不建议

class Goods:
    __discount = 0.8    # 类的私有属性
    def __init__(self,name,price):
        self.name = name
        self.__price = price

    @property        # 只读
    def price(self):
        return self.__price * Goods.__discount

    @price.setter      # 可写
    def price(self,new_price):
        self.__price = new_price

    @price.deleter
    def price(self):
        del self.__price    # 只能删除self赋值的命名
#       del self.name
        print(‘在执行删除操作啦！‘)
apple = Goods(‘apple‘,20)
print(apple.price)
apple.price = 40
print(apple.price)

del apple.price     # 删除会执行price.deleter里的
# print(apple.price)          # 因为删掉了__price，所以再次print会报错

from collections import namedtuple

Course = namedtuple(‘Course‘,[‘price‘,‘period‘,‘name‘])
python = Course(20000,‘6 months‘,‘python‘)
print(python.name)