两个类，一个是 Student, 另一个是 WorkingStudent，WorkingStudent 比 Student 多了一个 salary 属性，如果写成两个独立的类，代码如下：
class Student:
def __init__(self, name, school): # dunder 函数，构造函数
self.name = name
self.school = school
self.marks = [] # 分数
def average(self): # 计算平均分
return sum(self.marks) / len(self.marks)
class WorkingStudent:
def __init__(self, name, school, salary):
self.name = name
self.school = school
self.marks = []
self.salary = salary # 工资
def average(self):
return sum(self.marks) / len(self.marks)
这种写法，大部分代码都是重复的，为了避免重复，改为使用继承，使WorkingStudent 继承 Student：
class Student:
def __init__(self, name, school):
self.name = name
self.school = school
self.marks = []
def average(self):
return sum(self.marks) / len(self.marks)
class WorkingStudent(Student):
def __init__(self, name, school, salary):
super().__init__(name, school) # super() 是 Student
self.salary = salary
