day25 类的封装和类的绑定方法

1、封装（略）
2、在封装的基础上，我可以将装到对象或者类中的属性给隐藏起来
注意：
    （1）在定义类或者初始化对象时，在属性前加__,就会将该属性隐藏起来
        但该隐藏起始只是一种变形_类名__属性名，并没有真的隐藏起来

    （2）该变形操作是在类定义阶段扫描语法时发生的变形，类定义之后添加的__开头的属性不会发生变形

    （3）该隐藏是对外不对内

    (4) 在继承中，父类如果不想让子类覆盖自己的方法，可以将方法定义为私有的？？？

例11
class Student:
    __school = "oldboy"  # _Student__school = "oldboy"

    def __init__(obj, x, y, z):
        obj.__name = x  # obj._Student__name = x
        obj.age = y
        obj.gender = z

    def __choose(self):  # obj._Student__choose
        print("%s 正在选课" %self.name)


stu_obj1 = Student("冯疯子", 18, "female")
stu_obj1.__x=111
print(stu_obj1.__dict__)
print(stu_obj1.__x)



print(stu_obj1.__dict__)
print(stu_obj1._Student__name)

print(Student.__dict__)
print(Student._Student__school)
print(stu_obj1._Student__school)

隐藏属性的意义何在
1、把数据属性隐藏起来的意义是：在类内开放接口，让外界使用者通过接口来操作属性值，我们可以在接口之上附加任意的逻辑
                              来严格控制外界使用者对属性的操作

class Student:
    __school = "oldboy"  # _Student__school = "oldboy"

    def __init__(obj, x, y, z):
        obj.__name = x  # obj._Student__name = x
        obj.__age = y
        obj.gender = z

    def __choose(self):  # obj._Student__choose
        print("%s 正在选课" % self.name)

    def get_name(self):
        print(self.__name)  # print(self._Student__name)

    def set_age(self,x):
        if type(x) is not int:
            print("年龄必须是整型，傻叉")
            return
        self.__age = x

    def get_age(self):
        print(self.__age)

    def del_age(self):
        del self.__age

stu_obj1 = Student("冯疯子", 18, "female")
# stu_obj1.get_name()


# stu_obj1.set_age("asfdasfdasfafd")
stu_obj1.set_age(19)
stu_obj1.get_age()
# print(stu_obj1.__dict__)

2、把功能属性隐藏起来:隔离复杂度

class ATM:
    def __card(self):
        print('插卡')
    def __auth(self):
        print('用户认证')
    def __input(self):
        print('输入取款金额')
    def __print_bill(self):
        print('打印账单')
    def __take_money(self):
        print('取款')

    def withdraw(self):
        self.__card()
        self.__auth()
        self.__input()
        self.__print_bill()
        self.__take_money()

a=ATM()
a.withdraw()

例1

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

    @property
    def bmi(self):
        return self.weight / (self.height ** 2)


p = People('egon', 1.81, 70)
p.height = 1.84
print(p.bmi())

例2

class Student:
    __school = "oldboy"  # _Student__school = "oldboy"

    def __init__(obj, x, y, z):
        obj.__name = x
        obj.__age = y
        obj.gender = z

    def get_name(self):
        print("访问控制")
        return self.__name

    def set_name(self,x):
        print("赋值控制")
        self.__name = x

    def del_name(self):
        print("删除控制")
        del self.__name

    def get_age(self):
        return self.__age

    def set_age(self, x):
        if type(x) is not int:
            print("年龄必须是整型，傻叉")
            return
        self.__age = x

    def del_age(self):
        print("不让删")


    age = property(get_age, set_age, del_age)
    name = property(get_name, set_name, del_name)


stu_obj1 = Student("冯疯子", 18, "female")

# print(stu_obj1.age)
# stu_obj1.age = "19"
# del stu_obj1.age
# print(stu_obj1.age)


print(stu_obj1.name)
# stu_obj1.name="EGON"
# del stu_obj1.name

例3:

class Student:
    __school = "oldboy"  # _Student__school = "oldboy"

    def __init__(obj, x, y, z):
        obj.__name = x
        obj.__age = y
        obj.gender = z

    @property
    def name(self):
        print("访问控制")
        return self.__name

    @name.setter
    def name(self, x):
        print("赋值控制")
        self.__name = x

    @name.deleter
    def name(self):
        print("删除控制")
        del self.__name


stu_obj1 = Student("冯疯子", 18, "female")

stu_obj1.name

类中的定义的函数
1 绑定方法:谁来调用就会将谁当作第一个参数传入
 (1)绑定给对象的方法:类中定义的函数默认就是绑定给对象的方法,应该是由对象调用,会把对象当作第一个参数传入
 (2)绑定给类的方法:在类中的函数上加一个装饰器@classmethod,该函数就绑定给类了,应该是由类来调用,会把类当作第一个参数传入

2 非绑定方法:既不与类绑定也不与对象绑定,就是一个普通的函数,谁都可以来调用,没有自动传参的效果,
 在函数上添加装饰器@staticmethod

class People:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def tell_info(self):
        print("<%s:%s>" % (self.name, self.age))

    @classmethod
    def f1(cls):
        print(cls)

    @staticmethod
    def f2(x,y,z):
        print(x,y,z)


p1=People('egon',18)
# p1.tell_info()

# print(p1.tell_info)
# print(People.f1)

# People.f1()

# print(p1.f2)
# print(People.f2)
p1.f2(1,2,3)
People.f2(1,2,3)

例如:

import uuid
import settings

class MySQL:
    def __init__(self,ip,port):
        self.mid = self.__create_id()
        self.ip = ip
        self.port = port

    def tell_info(self):
        print("%s:<%s:%s>" %(self.mid,self.ip,self.port))

    @staticmethod
    def __create_id():
        return uuid.uuid4()

    @classmethod
    def from_conf(cls):
        return cls(settings.IP, settings.PORT)
        #IP = "127.0.0.1" settings
        #PORT = 3306


# obj = MySQL("10.10.11.11",3306)
# obj.tell_info()


obj1=MySQL.from_conf()
obj1.tell_info()