在Python类继承中继承docstrings

"""
doc_inherit decorator

Usage:

class Foo(object):
    def foo(self):
        "Frobber"
        pass

class Bar(Foo):
    @doc_inherit
    def foo(self):
        pass 

Now,Bar.foo.__doc__ == Bar().foo.__doc__ == Foo.foo.__doc__ == "Frobber"
"""

from functools import wraps

class DocInherit(object):
    """
    Docstring inheriting method descriptor

    The class itself is also used as a decorator
    """

    def __init__(self,mthd):
        self.mthd = mthd
        self.name = mthd.__name__

    def __get__(self,obj,cls):
        if obj:
            return self.get_with_inst(obj,cls)
        else:
            return self.get_no_inst(cls)

    def get_with_inst(self,cls):

        overridden = getattr(super(cls,obj),self.name,None)

        @wraps(self.mthd,assigned=('__name__','__module__'))
        def f(*args,**kwargs):
            return self.mthd(obj,*args,**kwargs)

        return self.use_parent_doc(f,overridden)

    def get_no_inst(self,cls):

        for parent in cls.__mro__[1:]:
            overridden = getattr(parent,None)
            if overridden: break

        @wraps(self.mthd,**kwargs):
            return self.mthd(*args,overridden)

    def use_parent_doc(self,func,source):
        if source is None:
            raise NameError,("Can't find '%s' in parents"%self.name)
        func.__doc__ = source.__doc__
        return func

doc_inherit = DocInherit