类的实现

class People():
    def __init__ (self, name, sex, ID):
        self.name = name
        self.sex = sex
        self.ID = ID
        
    def print_data(self):
        print 'the person is %s %s %s' %(self.name, self.sex, self.ID)
        
P1 = People('Ivy', 'girl', 111)
#P1.print_data()
print P1.name      #猜到内容你可以修改哦

为了使用户不能猜到name等关键字,__加入可以让外部无法访问

class People():
    def __init__ (self, name, sex, ID):
        self.__name = name
        self.__sex = sex
        self.__ID = ID
        
    def print_data(self):
        print 'the person is %s %s %s' %(self.__name, self.__sex, self.__ID)
        
P1 = People('Ivy', 'girl', 111)
#P1.print_data()
print P1.__name   #没有办法啦，私有的函数不能访问

2)如何修改外部无法访问的参数？主要作用是对其添加的进行判断

class People():
    def __init__ (self, name, sex, ID):
        self.__name = name
        self.__sex = sex
        self.__ID = ID
        
    def print_data(self):
        print 'the person is %s %s %s' %(self.__name, self.__sex, self.__ID)
    
    def get_ID(self, reID):
        self.__ID = reID
        if reID > 150:
            print 'large number'
        else:
            print 'small number'                    
       
P1 = People('Ivy', 'girl', '111')
P1.get_ID(123)
P1.print_data()