Python继承文档字符串错误 'read only'

Question

我已经阅读了这里有关此主题的所有其他帖子，但由于其中大多数都已经很旧了，所以我觉得最好用我自己的问题打开一个新帖子，因为那里提出的解决方案对我不起作用，但我还没有在评论中看到任何投诉。

例如提出的解决方案here给我错误:

AttributeError: 'NoneType' object attribute '__doc__' is read-only

第二个提出的解决方案there给我:

TypeError: Error when calling the metaclass bases
    readonly attribute

我发现的关于文档字符串只读的唯一引用是 here

我正在使用Python 2.7.9。我做错了什么或者 doc 属性真的是只读的吗？

这是 SSCCE 以及另一篇文章的解决方案之一:

# decorator proposed in https://stackoverflow.com/a/8101598/551045
def fix_docs(cls):
    for name, func in vars(cls).items():
        if not func.__doc__:
            print func, 'needs doc'
            for parent in cls.__bases__:
                parfunc = getattr(parent, name)
                if parfunc and getattr(parfunc, '__doc__', None):
                    func.__doc__ = parfunc.__doc__
                    break
    return cls



class X(object):
    """
    some doc
    """

    def please_implement(self):
        """
        I have a very thorough documentation
        :return:
        """
        raise NotImplementedError


@fix_docs
class SpecialX(X):

    def please_implement(self):
        return True


print help(SpecialX.please_implement)

输出:

Traceback (most recent call last):
None needs doc
  File "C:/Users/RedX/.PyCharm2016.2/config/scratches/scratch.py", line 29, in <module>
    class SpecialX(X):
  File "C:/Users/RedX/.PyCharm2016.2/config/scratches/scratch.py", line 9, in fix_docs
    func.__doc__ = parfunc.__doc__
AttributeError: 'NoneType' object attribute '__doc__' is read-only

使用固定装饰器:

import types

def fix_docs(cls):
    for name, func in vars(cls).items():
        if isinstance(func, types.FunctionType) and not func.__doc__:
            print func, 'needs doc'
            for parent in cls.__bases__:
                parfunc = getattr(parent, name, None)
                if parfunc and getattr(parfunc, '__doc__', None):
                    func.__doc__ = parfunc.__doc__
                    break
    return cls


class DocStringInheritor(type):
    """
    A variation on
    http://groups.google.com/group/comp.lang.python/msg/26f7b4fcb4d66c95
    by Paul McGuire
    """
    def __new__(meta, name, bases, clsdict):
        if not('__doc__' in clsdict and clsdict['__doc__']):
            for mro_cls in (mro_cls for base in bases for mro_cls in base.mro()):
                doc=mro_cls.__doc__
                if doc:
                    clsdict['__doc__']=doc
                    break
        for attr, attribute in clsdict.items():
            if not attribute.__doc__:
                for mro_cls in (mro_cls for base in bases for mro_cls in base.mro()
                                if hasattr(mro_cls, attr)):
                    doc=getattr(getattr(mro_cls,attr),'__doc__')
                    if doc:
                        attribute.__doc__=doc
                        break
        return type.__new__(meta, name, bases, clsdict)

class X(object):
    """
    some doc
    """
    #__metaclass__ = DocStringInheritor
    x = 20

    def please_implement(self):
        """
        I have a very thorough documentation
        :return:
        """
        raise NotImplementedError

    @property
    def speed(self):
        """
        Current speed in knots/hour.
        :return:
        """
        return 0

    @speed.setter
    def speed(self, value):
        """

        :param value:
        :return:
        """
        pass

@fix_docs
class SpecialX(X):

    def please_implement(self):
        return True

    @property
    def speed(self):
        return 10

    @speed.setter
    def speed(self, value):
        self.sp = value


class VerySpecial(X):
    p = 0
    """doc"""

    def please_implement(self):
        """

        :return bool: Always false.
        """
        return False

    def not_inherited(self):
        """
        Look at all these words!
        :return:
        """

help(X.speed)
help(SpecialX.speed)
help(SpecialX.please_implement)
help(VerySpecial.please_implement)
help(VerySpecial.not_inherited)

输出:

<function please_implement at 0x026E4AB0> needs doc
Help on property:

    Current speed in knots/hour.
    :return:

Help on property:


Help on method please_implement in module __main__:

please_implement(self) unbound __main__.SpecialX method
    I have a very thorough documentation
    :return:

Help on method please_implement in module __main__:

please_implement(self) unbound __main__.VerySpecial method
    :return bool: Always false.

Help on method not_inherited in module __main__:

not_inherited(self) unbound __main__.VerySpecial method
    Look at all these words!
    :return:

Answer 1

使用 DocStringInheritor 的现已修复版本元类，

class DocStringInheritor(type):
    """
    A variation on
    http://groups.google.com/group/comp.lang.python/msg/26f7b4fcb4d66c95
    by Paul McGuire
    """
    def __new__(meta, name, bases, clsdict):
        if not('__doc__' in clsdict and clsdict['__doc__']):
            for mro_cls in (mro_cls for base in bases for mro_cls in base.mro()):
                doc=mro_cls.__doc__
                if doc:
                    clsdict['__doc__']=doc
                    break
        for attr, attribute in clsdict.items():
            if not attribute.__doc__:
                for mro_cls in (mro_cls for base in bases for mro_cls in base.mro()
                                if hasattr(mro_cls, attr)):
                    doc=getattr(getattr(mro_cls,attr),'__doc__')
                    if doc:
                        if isinstance(attribute, property):
                            clsdict[attr] = property(attribute.fget, attribute.fset, attribute.fdel, doc)
                        else:
                            attribute.__doc__=doc
                        break
        return type.__new__(meta, name, bases, clsdict)


class X(object):
    __metaclass__ = DocStringInheritor

    """
    some doc
    """
    x = 20

    def please_implement(self):
        """
        I have a very thorough documentation
        :return:
        """
        raise NotImplementedError

    @property
    def speed(self):
        """
        Current speed in knots/hour.
        :return:
        """
        return 0

    @speed.setter
    def speed(self, value):
        """

        :param value:
        :return:
        """
        pass

class SpecialX(X):

    def please_implement(self):
        return True

    @property
    def speed(self):
        return 10

    @speed.setter
    def speed(self, value):
        self.sp = value


class VerySpecial(X):
    p = 0
    """doc"""

    def please_implement(self):
        """

        :return bool: Always false.
        """
        return False

    def not_inherited(self):
        """
        Look at all these words!
        :return:
        """

help(X.speed)
help(SpecialX.speed)
help(SpecialX.please_implement)
help(VerySpecial.please_implement)
help(VerySpecial.not_inherited)

产量

Help on property:

    Current speed in knots/hour.
    :return:

Help on property:

    Current speed in knots/hour.
    :return:

Help on function please_implement in module __main__:

please_implement(self)
    I have a very thorough documentation
    :return:

Help on function please_implement in module __main__:

please_implement(self)
    :return bool: Always false.

Help on function not_inherited in module __main__:

not_inherited(self)
    Look at all these words!
    :return: