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
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