in reply to https://gist.github.com/podhmo/5984902

delegation_ky.py

class CoreModel(object):
    def __init__(self, name, published=False):
        self.name = name
        self.published = published

    def publish(self):
        self.publish = True
    def unpublish(self):
        self.publish = False


class DelegationMeta(type):
    def __new__(cls, name, bases, attrs):
        if "Delegation" in attrs:
            Delegation = attrs["Delegation"]
            target = Delegation.target
            for fs in Delegation.fields:
                if not isinstance(fs, (tuple, list)):
                    f, after_access = fs, lambda x: x
                else:
                    f, after_access = fs
                def accessor(self, k=f, a=after_access):
                    return a(getattr(getattr(self, target), k))
                attrs[f] = property(accessor)
        return type.__new__(cls, name, bases, attrs)


class WrappedModel5(object):
    __metaclass__ = DelegationMeta
    class Delegation:
        target = "core"
        fields = ["name", "published"]

    def __init__(self, core):
        self.core = core


class WrappedModel6(object):
    __metaclass__ = DelegationMeta
    class Delegation:
        target = "core"
        fields = [("name", lambda x: x * 2), "published"]

    def __init__(self, core):
        self.core = core


wm5 = WrappedModel5(CoreModel("foo"))
assert wm5.name == "foo"
assert wm5.published == False

wm6 = WrappedModel6(CoreModel("foo"))
assert wm6.name == "foofoo"
assert wm6.published == False