访问子类中的父级属性作为classMethod

发布于 2025-02-13 01:06:53 字数 1646 浏览 0 评论 0 原文

我有以下效果很好的代码：

class Person:
    def __init__(self, fname, lname) -> None:
        self.firstname = fname
        self.lastname = lname

    def __repr__(self) -> str:
        return f'{self.firstname} {self.lastname}'

class Student(Person):
    def __init__(self, fname, lname, year) -> None:
        super().__init__(fname, lname)
        self.gradyear = year

    def __repr__(self) -> str:
        return f'{self.firstname} {self.lastname} passed in {self.gradyear}'

    def welcome(self):
        print(f'Welcome, {self.firstname} {self.lastname} you passed out in {self.gradyear}')

x = Person("John", "Doe")
y = Student("John", "Doe", 1988)

y.welcome()

但是，我希望将最后一个方法定义为classMethod。因此，如果我进行以下更改，则代码会失败。

class Person:
    def __init__(self, fname, lname) -> None:
        self.firstname = fname
        self.lastname = lname

    def __repr__(self) -> str:
        return f'{self.firstname} {self.lastname}'

class Student(Person):
    def __init__(self, fname, lname, year) -> None:
        super().__init__(fname, lname)
        self.gradyear = year

    def __repr__(self) -> str:
        return f'{self.firstname} {self.lastname} passed in {self.gradyear}'

    @classmethod
    def welcome(cls):
        print(f'Welcome, {cls.firstname} {cls.lastname} you passed out in {cls.gradyear}')

x = Person("John", "Doe")
y = Student("John", "Doe", 1988)

y.welcome()

我会出现一个错误，如下所示：

AttributeError: type object 'Student' has no attribute 'firstname'

我意识到Python正在看儿童课 - 属性的学生。但是，通过继承，它也应查看父母应该找到属性的父。

我在这里想念什么？

原文

I have the following code which works fine :

class Person:
    def __init__(self, fname, lname) -> None:
        self.firstname = fname
        self.lastname = lname

    def __repr__(self) -> str:
        return f'{self.firstname} {self.lastname}'

class Student(Person):
    def __init__(self, fname, lname, year) -> None:
        super().__init__(fname, lname)
        self.gradyear = year

    def __repr__(self) -> str:
        return f'{self.firstname} {self.lastname} passed in {self.gradyear}'

    def welcome(self):
        print(f'Welcome, {self.firstname} {self.lastname} you passed out in {self.gradyear}')

x = Person("John", "Doe")
y = Student("John", "Doe", 1988)

y.welcome()

However, I wish to define the last method - welcome - as a classmethod. So if I do the following change, the code fails.

class Person:
    def __init__(self, fname, lname) -> None:
        self.firstname = fname
        self.lastname = lname

    def __repr__(self) -> str:
        return f'{self.firstname} {self.lastname}'

class Student(Person):
    def __init__(self, fname, lname, year) -> None:
        super().__init__(fname, lname)
        self.gradyear = year

    def __repr__(self) -> str:
        return f'{self.firstname} {self.lastname} passed in {self.gradyear}'

    @classmethod
    def welcome(cls):
        print(f'Welcome, {cls.firstname} {cls.lastname} you passed out in {cls.gradyear}')

x = Person("John", "Doe")
y = Student("John", "Doe", 1988)

y.welcome()

I get an error as follows :

AttributeError: type object 'Student' has no attribute 'firstname'

I realize that Python is looking at the child class - Student for the attributes. However, by inheritance, it should also look at the Parent, where it should find the attributes.

What am I missing here ?

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递刀给你 2025-02-20 01:06:53

如果方法被标记为 @ClassMethod ，则仅具有对类的访问，而不能访问该类的实例。这意味着您无法访问实例变量。它与继承无关，您甚至无法在该方法中访问 gradyear 属性。表示 __ Init __（）中设置的任何变量无法通过 @ClassMethod 访问。您可以阅读有关 @ClassMethod 。