一、类和实例

二、访问限制

使用双下划线__将对象隐藏，相当于private

class Student(object):

    def __init__(self, name, gender):
        self.__name = name
        self.__gender = gender

    def get_name(self):
        return self.__name

    def get_gender(self):
        return self.__gender

    def set_gender(self, gender):
        self.__gender = gender

bart = Student('Bart', 'male')
if bart.get_gender() != 'male':
    print('测试失败!')
else:
    bart.set_gender('female')

三、继承和多态

四、实例属性和类属性

如果Student类本身需要绑定一个属性呢？可以直接在class中定义属性，这种属性是类属性，归Student类所有：

class Student(object):
    name = 'Student'

class Student(object):

    count = 0

    def __init__(self, name):

        self.name = name

        Student.count = Student.count+1
# 测试:
if Student.count != 0:
    print('测试失败!')
else:
    bart = Student('Bart')
    if Student.count != 1:
        print('测试失败!')
    else:
        lisa = Student('Bart')
        if Student.count != 2:
            print('测试失败!')
        else:
            print('Students:', Student.count)
            print('测试通过!')