Python object hierarchy; Referencing an owner instance?

Question

Is there no magic python way of accessing the instance of the class that has a reference to the current self inside it? ie:

class A(object):
    def __init__(self):
        self.B = B()

    def say_hi(self):
        print "Hi"

class B(object)
    def __init__(self):
        __get_owner_ref__.say_hi()

A()

get_owner_ref being the magic bullet that does not exist. Is there a feature in python for this behaviour?

Yes I know I could pass a reference in to the constructor, but I'm looking for a more elegant solution.

Answer 1

No, You'd have to do something like this

class A(object):
    def __init__(self):
        self.B = B(parent=self)

    def say_hi(self):
        print "Hi"

class B(object)
    def __init__(self, parent):
        self.parent = parent   # you don't need to do this, but it might be a good idea
        parent.say_hi()

A()

Answer 2

On the second thought, what you're looking for pretty closely resembles descriptors. Consider:

class Agent(object):
    def __get__(self, obj, objtype):
        print 'Agent %s called from %s ' % (id(self), obj.name)

class X(object):
    agent = Agent()

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

a = X('Foo')
a.agent

b = X('Bar')
b.agent

Here the agent is attached to two different instances and "knows" each time which instance wants to talk to him.