Python 无法实例化抽象类......使用抽象方法
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/31457855/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Can't instantiate abstract class ... with abstract methods
提问by josuebrunel
I'm working on a kind of lib, and for a weird reason i have this error.
我正在开发一种库，但出于一个奇怪的原因，我遇到了这个错误。
Sorry couldn't just copy and paste it
抱歉不能只是复制和粘贴它
I went on the basis that the code below works
我的基础是下面的代码有效
test.py
测试文件
import abc
import six
@six.add_metaclass(abc.ABCMeta)
class Base(object):
@abc.abstractmethod
def whatever(self,):
raise NotImplementedError
class SubClass(Base):
def __init__(self,):
super(Base, self).__init__()
self.whatever()
def whatever(self,):
print("whatever")
In the python shell
在 python 外壳中
>>> from test import *
>>> s = SubClass()
whatever
Why for my rostermodule i'm having this error
为什么我的名册模块出现此错误
Can't instantiate abstract class Player with abstract methods _Base__json_builder, _Base__xml_builder
Thanks in advance
提前致谢
采纳答案by Anand S Kumar
Your issue comes because you have defined the abstract methods in your base abstract class with __(double underscore) prepended. This causes python to do name manglingat the time of definition of the classes.
您的问题出现是因为您已经在基础抽象类中定义了带有__（双下划线）前缀的抽象方法。这会导致 python在定义类时进行名称修改。
The names of the function change from __json_builderto _Base__json_builderor __xml_builderto _Base__xml_builder. And this is the name you have to implement/overwrite in your subclass.
函数名称从__json_builder到_Base__json_builder或__xml_builder变为_Base__xml_builder。这是您必须在子类中实现/覆盖的名称。
To show this behavior in your example -
要在您的示例中显示此行为 -
>>> import abc
>>> import six
>>> @six.add_metaclass(abc.ABCMeta)
... class Base(object):
... @abc.abstractmethod
... def __whatever(self):
... raise NotImplementedError
...
>>> class SubClass(Base):
... def __init__(self):
... super(Base, self).__init__()
... self.__whatever()
... def __whatever(self):
... print("whatever")
...
>>> a = SubClass()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: Can't instantiate abstract class SubClass with abstract methods _Base__whatever
When I change the implementation to the following, it works
当我将实现更改为以下内容时，它会起作用
>>> class SubClass(Base):
... def __init__(self):
... super(Base, self).__init__()
... self._Base__whatever()
... def _Base__whatever(self):
... print("whatever")
...
>>> a = SubClass()
whatever
But this is very tedious , you may want to think about if you really want to define your functions with __(double underscore) . You can read more about name mangling here.
但这很乏味，你可能要考虑一下你是否真的想用__(double underscore)定义你的函数。您可以在此处阅读有关名称修改的更多信息。
