Class decorator for declaring delegated methods

def_delegator.py

class Delegated(object):
    def __init__(self, delegated_name, attr):
        self.attr_name = attr
        self.delegated_name = delegated_name

    def __get__(self, instance, owner):
        if instance is None:
            return self
        else:
            return getattr(self.delegate(instance), self.attr_name)

    def __set__(self, instance, value):
        setattr(self.delegate(instance), self.attr_name, value)

    def __delete__(self, instance):
        delattr(self.delegate(instance), self.attr_name)

    def delegate(self, instance):
        return getattr(instance, self.delegated_name)


class delegate(object):
    def __init__(self, src, *attrs):
        self.src = src
        self.attrs = attrs

    def __call__(this, cls):
        for attr in this.attrs:
            setattr(cls, attr, Delegated(this.src, attr))
        return cls

class Bar:
    def grok(self):
        return 'grok'


@delegate('bar', 'grok')
class Foo:
    def __init__(self):
        self.bar = Bar()

        
foo = Foo()
foo.grok()
# 'grok'
foo.grok = 'bar'
foo.grok
# 'bar'

Similar to def_delegator in Ruby, allows to forward/delegate attributes and methods to some attribute on the object.
Supports setting and deleting.