When I access the attribute in Python with the usual dot operator I get a tuple. What I'd really like though is an object of type <class 'scitbx.matrix.col'>, which is what I passed to the constructor of the object in Python.
This would be nice indeed but is a little tricky to implement. The C++ wrapper code would need to import scitbx.matrix. It's entirely possible but I always shied away from introducing this dependency.
I found I had to add
from cctbx.array_family import flex
to the package __init__.py where my C++ extension is imported,
This import piggy-backs a whole bunch of loosely related from-and-to-tuple conversions; see scitbx/array_family/boost_python/flex_ext.cpp. I had long discussions with Luc about this when he started using cctbx, because from a purists standpoint centralizing all the conversions in flex_ext.cpp breaks modularity. However, the discussions didn't lead to practical alternatives, and I believe the current solution works well in practice.
Ralf