python中的类继承

Question

我正在解决这个问题：

考虑以下类的层次结构：

 class Person(object): def __init__(self, name): self.name = name def say(self, stuff): return self.name + ' says: ' + stuff def __str__(self): return self.name class Lecturer(Person): def lecture(self, stuff): return 'I believe that ' + Person.say(self, stuff) class Professor(Lecturer): def say(self, stuff): return self.name + ' says: ' + self.lecture(stuff) class ArrogantProfessor(Professor): def say(self, stuff): return 'It is obvious that ' + self.say(stuff) 

如上所述，当使用Arrogant Professor类时，此代码会导致无限循环。

更改ArrogantProfessor的定义，以便实现以下行为：

 e = Person('eric') le = Lecturer('eric') pe = Professor('eric') ae = ArrogantProfessor('eric') e.say('the sky is blue') #returns eric says: the sky is blue le.say('the sky is blue') #returns eric says: the sky is blue le.lecture('the sky is blue') #returns believe that eric says: the sky is blue pe.say('the sky is blue') #returns eric says: I believe that eric says: the sky is blue pe.lecture('the sky is blue') #returns believe that eric says: the sky is blue ae.say('the sky is blue') #returns eric says: It is obvious that eric says: the sky is blue ae.lecture('the sky is blue') #returns It is obvious that eric says: the sky is blue 

我的解决方案是：

class ArrogantProfessor(Person):
    def say(self, stuff):
        return Person.say(self, ' It is obvious that ') +  Person.say(self,stuff)
    def lecture(self, stuff):
        return 'It is obvious that  ' + Person.say(self, stuff)

但是检查器只给出了这个解决方案的一半标记。 我犯的错误是什么，以及此代码失败的测试用例是什么？ （我是python的新手，不久前就开始学习类。）

Answer 1

你可能应该使用super()而不是硬连接类Person ：

class ArrogantProfessor(Person):
    def say(self, stuff):
        return super(ArrogantProfessor, self).say(self.lecture(stuff))
    def lecture(self, stuff):
        return 'It is obvious that ' + super(ArrogantProfessor, self).say(stuff)

Answer 2

有人说：

class ArrogantProfessor(Professor): 

但是你这样做了：

class ArrogantProfessor(Person): 

导致成绩减半。

Answer 3

作为一名编码hw的前评级者，我认为，你应该产生所需的输出而不使ArrogantProfessor成为一个Person 。 毕竟，类名表明它仍然应该是Professor子类。

Answer 4

他可能希望你真正得到父类。 这样做的方法很简单。

Python2 / 3：

class ArrogantProfessor(Professor):
    def say(self, stuff):
        return 'It is obvious that ' + super(ArrogantProfessor, self).say(stuff)

仅限Python 3：

class ArrogantProfessor(Professor):
    def say(self, stuff):
        return 'It is obvious that ' + super().say(stuff)

在任何一种情况下， ae.say("something")都应该返回：

"It is obvious that eric says: I believe that eric says: something"

这是因为父类是Professor ，而不是Person 。

同样，在你的课堂上，你应该做：

def lecture(self, stuff):
    return 'I believe that ' + super(Lecturer, self).say(self, stuff) # or the Python3 version if you're using that

但是，你想要的是什么并不是很清楚。

Answer 5

这应该是：

class ArrogantProfessor( Professor ):
    def lecture(self, stuff):
        return 'It is obvious that ' +  Person.say(self,stuff)

您不必在ArrogantProfessor定义say() ，因为它已经在Professor定义，它将使用子类中定义的lecture()方法。

Answer 6

如果不知道他们想要教你什么，就有点难以说。 一个可能的猜测是，你正在被教授继承，如果他们已超越超级 ，他们可能希望你利用它来让ArrogantProfessor的输出看起来像：

eric says: It is obvious that STUFF

其中STUFF是你传入的字符串。

Answer 7

     class Professor(Lecturer): 
        def say(self, stuff): 
            return "Prof. " + self.name + ' says: ' + self.lecture(stuff)

     class ArrogantProfessor( Professor ):
        def lecture(self, stuff):         
            return 'It is obvious that I believe that ' + Person.say(self, stuff)

Answer 8

对于第二部分，正确答案是：

class ArrogantProfessor(Professor):
    def lecture(self, stuff):
        return 'It is obvious that ' +  Lecturer.lecture(self,stuff)

Answer 9

对于第一部分，代码是：

class ArrogantProfessor( Professor ):
def lecture(self, stuff):
    return 'It is obvious that ' +  Person.say(self,stuff)

对于第二部分，代码是：

class ArrogantProfessor(Professor):
def lecture(self, stuff):
    return 'It is obvious that I believe that ' +  Person.say(self,stuff)

对于第三部分，代码是：

class Professor(Lecturer):
 def say(self, stuff): 
     return 'Prof. ' + self.name + ' says: ' + self.lecture(stuff)

希望它有用