registering simple conversions from/to python

I'd like to pythonise my classes a little by allowing tuples to be passed to
and from the data values.

In python in would look something like this:

class C(object):
    def __init__(self, x=0.0, y=0.0):
        self.x = x
        self.y = y

    def get_xy(self):
        return self.x, self.y

    def set_xy(self, xy):
        self.x, self.y = xy

    xy = property(get_xy, set_xy)


I guess I would start by created a pair<x, x> object, and then register
inward and outward conversions for it.

Is there a simple recipe for registering these conversions?

Cheers,
Brett