Murray Cumming wrote:
On Fri, 2009-02-27 at 08:34 -0800, Alex Mohr wrote:
Murray Cumming wrote:
I can't find any definitive documentation that tells me how I should get a boost::python::object to wrap an existing PyObject*. I guess that there's a way to do it that uses an existing reference, and a way that takes an extra reference. You can construct a boost::python::object with a boost::python::handle<>. boost::python::handle<> is sort of a "smart" PyObject *. It manages the python object reference count automatically.
Oh, I assumed that boost::python::object did this already.
If not, is there any reason not to use boost::python::handle<boost::python::object> everywhere instead of a boost::python::object?
One of my main reasons for using boost::python instead of the C API is to avoid worrying so much about the reference counting. For instance, I don't want to explicitly increment the ref when returning a PyObject, or remember whether I should take a ref when given a PyObject from various functions.
I believe, but could be wrong, that boost::python::objects must be made from handles. If not that's not a requirement, it's at least a strong suggestion. That way, the underlying handle in the object will handle the reference counting for you. The way I understand it, the handle takes care of the reference counting, and the object is a wrapper to make it easier to interact with the pointer to PyObject in a more OO-like manner. Also, I'm not sure you can make a boost::python::handle<boost::python::object>. The instance the handle points to should be laid out like a PyObject. (Remember, the underlying Python code is C-based, so pointer layout is required to start the same to approximate inheritance.) I don't think boost::python::object can make that guarantee. -- Anthony Foglia Princeton Consultants (609) 987-8787 x233