内容概要

• 案例
• 绑定方法
• 非绑定方法（静态方法）
• 如何隐藏属性
• property装饰器

内容详细

案例

            题目：
                1. 定义一个类，产生一堆对象

                2. 统计产生了多少个对象
                    '''思路：定义一个计数器，每产生一个对象，计数器加1'''

               class Student():
                school = 'SH'
                count = 0  # 专门用来计数

                def __init__(self, name, age):
                    # self => stu => {'name':'ly', 'age': 18, 'count'：1}
                    # self => stu1 => {'name':'ly1', 'age': 18, 'count'：1}
                    # self => stu2 => {'name':'ly2', 'age': 18, 'count'：1}
                    self.name = name
                    self.age = age
                    # self.count = self.count + 1
                    # Student.count += 1
                    # self.__class__  # Student
                    self.__class__.count += 1

绑定方法

            绑定方法分为2种：
                1. 绑定给对象的
                    class Student():
                def __init__(self, name, age, gender):
                    self.name = name
                    self.age = age
                    self.gender = gender

                # 绑定给对象的方法，对象来调用，会把自己当成第一个参数传到函数里面self
                def tell_info(self):
                    print('name: %s，age:%s, gender:%s' % (self.name, self.age, self.gender))


                    stu = Student('ly', 18, 'male')
                    # print(stu.name)
                    stu.tell_info() # stu.tell_info(stu)

                2. 绑定给类的

            class Mysql():
                def __init__(self, ip, port):
                    self.ip = ip
                    self.port = port

                @classmethod  # 该方法绑定给类了，以后有类来调用，会自动把类名当成第一个参数传过来，cls
                def from_conf(cls):
                    # cls => Oracle
                    # obj = Oracle(settings.IP, settings.PORT)
                    obj = cls(settings.IP, settings.PORT)
                    return obj
             Mysql.from_conf()

非绑定方法

            # 既不绑定给类，也不绑定给对象
            class Student():
                school = 'SH'
                def __init__(self, name, age):
                    self.name = name
                    self.age = age

                @staticmethod  # 静态方法
                def create_id():
                    import uuid
                    return uuid.uuid4()

            stu = Student('ly', 18)

            # print(stu.create_id())
            # print(Student.create_id())
            print(stu.create_id())

如何隐藏属性

            # 1. 如何隐藏
                    # 1. 如何隐藏
            '''
                1. 在类定义阶段，发生了语法上的变形_类名__属性名
                2. 隐藏对外不对内
                3. 只有在类定义阶段发生变形，其他情况都不发生变形了

            为什么要隐藏: 类里面的隐藏属性， 类外部可以使用，但是目的不是让类外部使用的，类外部要是想用，在类内部开放接口进行访问
                        可以达到对外部数据的严格控制
            '''
            class Student():
                __school = 'SH' # _Student__school  => _类名__属性名
                def __init__(self, name, age):
                    self.__name = name
                    self.age = age

                def __tell_info(self):  # _Student__tell_info  => _类名__函数名
                    print('name: %s, age: %s' % (self.__name, self.age))

                def get_school(self):
                    return self.__school  # self._Student__school

                def set_school(self, v):
                    if type(v) is not str:
                        print('数据类型不合法')
                    # if isinstance(v, str):
                        return
                    self.__school = v

            # 2. 为何隐藏

property装饰器

            class Student():
                __school = 'SH'  # _Student__school  => _类名__属性名

                def __init__(self, name, age):
                    self.__name = name
                    self.age = age

                def __tell_info(self):  # _Student__tell_info  => _类名__函数名
                    print('name: %s, age: %s' % (self.__name, self.age))

                @property  # 把方法伪装成属性
                def name(self):
                    return "name:%s" % self.__name

                @name.setter
                def name(self, v):
                    if type(v) is not str:
                        print('数据类型不合法')
                    # if isinstance(v, str):
                        return
                    self.__name = v

                @name.deleter
                def name(self):
                    print('不让删')

            stu = Student('ly', 18)
            print(stu.get_name())

            stu.name = 123
            print(stu.name)

            del stu.name


            # 练习
            class Bmi():
                def __init__(self, height, weight):
                    self.height = height
                    self.weight = weight

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

            bmi = Bmi(1.8, 70)
            print(bmi.get_bmi)


            # 了解

            class Student():
                __school = 'SH'  # _Student__school  => _类名__属性名

                def __init__(self, name, age):
                    self.__name = name
                    self.age = age

                def __tell_info(self):  # _Student__tell_info  => _类名__函数名
                    print('name: %s, age: %s' % (self.__name, self.age))

                def get_name(self):
                    return "name:%s" % self.__name

                def set_name(self, v):
                    if type(v) is not str:
                        print('数据类型不合法')
                        # if isinstance(v, str):
                        return
                    self.__name = v

                def del_name(self):
                    print('不让删')

                # 了解
                name = property(get_name, set_name, del_name)


            stu = Student('ly', 18)
            # print(stu.xxx)

            stu.name = 'aaa'
            print(stu.name)