Scope troubles with a swap function

[Matthew D. Wood]

Ok, I've been banging my head against this for a sufficiently long time 
that I feel justified in presenting this personal challenge to the list.

How do you make a swap function? 

Everything in python is a reference, but creating a function that will 
swap the references is quite difficult (at least for me it is).

How do you make a function or a callable object instance that will do 
what the following code intends to do:

   def swap (heaven, hell) :
           purgatory = heaven
           heaven = hell
           hell = purgatory

In C++ this was a VERY easy function to write because you could pass 
things via reference; however, I don't want to write some sort of C 
extension for something as simple as swapping 2 variables.

I have been trying to abuse some sort of meta-variable, like __dict__ to 
do this, but I have done nothing more than confuse myself.  That and 
there is a lingering fear in my mind that if one or more of the 
to-be-swapped variables are in __methods__ or __members__ dicts, then I 
will definitely be lost.

That and if the __dict__, __methods__, __members__ approach is used, how 
does one deal with scoping?
       swap(g.h.var, a.q.member)

Thus, I present this problem to the list.