[C++-sig] boost::python, PyObject* members, and cyclic references

[Jim Bosch]

I am trying to wrap a class in which I'd like to expose some of its data 
as a numpy array, so in python it works like this:

 >>> o = array_holder()
 >>> a = o.array
 >>> a[4:6] = 3.14

Rather than constructing the array every time, I'd like to store the 
PyObject* (or something equivalent) in my array_holder wrapper, but I 
need to tie the lifetimes of 'o' and 'a' together, so nothing bad 
happens if someone does 'del o' while 'a' still exists.

The numpy array I'm constructing holds a reference to the PyObject that 
owns its data (which I assume I can get from 'object(this).ptr()'), so 
I'm not worried about that end.  And I assume something like 
'return_internal_reference' is what I'm looking for at the other end, 
but I'm not quite sure how to work out the details (do I return a 
'PyObject*', a 'handle', or an 'object'?)

Finally, there's the question of whether either of these will ever get 
deleted at all - do boost::python wrapped objects participate in cyclic 
gc?  If not, is there any way I can manually add it for this class (by 
suppling traverse and clear methods using the C API, for instance)?


Thanks!

Jim Bosch