'super' 对象没有属性 '_Parent__method'

Question

我已经阅读了所有关于此主题的类似帖子，但 none 我发现它们与我的问题相关，帮助我弄清楚发生了什么。

class A:
    def __init__(self, value):
        self.__value = value
        self.__conn = httpsconnection # Specifics don't matter

class B(A):
    def __init__(self, id, type, value):
        super().__init__(value)
        self.data = self.__create_sub_class(id, type)

    def __create_sub_class(self, id, type):
        self.__conn.request(...)
        ...
        return data

class C(B):
    def __init__(self, id, value):
        super().__init__(id, externalVariable, value)

我收到的错误是 AttributeError: 'C' object has no attribute '_B__conn'

class C 不应该从 B 继承变量，而 B 是从 A 继承变量吗？

Answer 1

如果您想在子classes 中使用这些名称，请不要使用前导双下划线名称。 __name 明确设计为使名称 class 私有 ，即仅对确切的 class 有用。这个想法是，您可以在框架中使用此类名称，而无需限制 subclasses 可以使用的名称。

这样的名字在编译时被破坏；他们有 _ClassName 前缀（使用当前的 class 名称）。如果您想表明名称是内部名称，只需使用单下划线名称即可（Python 没有实际的隐私模型，名称始终可访问）：

class A:
    def __init__(self, value):
        self._value = value
        self._conn = httpsconnection # Specifics don't matter

class B(A):
    def __init__(self, id, type, value):
        super().__init__(value)
        self.data = self._create_sub_class(id, type)

    def _create_sub_class(self, id, type):
        self._conn.request(...)
        ...
        return data

参见词法分析文档中的Reserved classes of identifiers：

__*
Class-private names. Names in this category, when used within the context of a class definition, are re-written to use a mangled form to help avoid name clashes between “private” attributes of base and derived classes.

和引用的 documentation on names:

Private name mangling: When an identifier that textually occurs in a class definition begins with two or more underscore characters and does not end in two or more underscores, it is considered a private name of that class. Private names are transformed to a longer form before code is generated for them. The transformation inserts the class name, with leading underscores removed and a single underscore inserted, in front of the name. For example, the identifier __spam occurring in a class named Ham will be transformed to _Ham__spam. This transformation is independent of the syntactical context in which the identifier is used.

'super' 对象没有属性 '_Parent__method'

'super' object has no attribute '_Parent__method'

python

class

subclass

python-3.x