Interaction pyroot <-> boost::python

Dear all,

currently, I am writing bindings of an amplitude analysis package (rootpwa, for python with boost::python. The analysis package uses a number of root classes which makes an interaction between pyroot and boost::python necessary.

For the most part, this works quite well. Unfortunately, I have run into a problem where I need some help: I am doing bindings for functions which return root objects. In python, the objects which are returned should behave like regular pyroot objects. I solved this with the following converter:


template<typename T>
PyObject* convertToPy(const T& cxxObj) {
	T* newCxxObj = new T(cxxObj);
	return TPython::ObjectProxy_FromVoidPtr(&newCxxObj, newCxxObj.ClassName());

Initially, I was assuming that the python garbage collection would take over the deletion of “newCxxObj”, but as it turns out, this is not the case, so the converter is a gaping memory leak. However, if I directly return a pointer to cxxObj, it might happen that cxxObj goes out of scope and I am returning a dangling pointer.

I also tried around with the boost::python return value policies, in particular return_value_policy<manage_new_object>(), but this results in a segmentation violation. I also stumbled upon the AsCObject() and SetOwnership(), but as far as I can tell, I cannot call these from C++ code, which would be necessary to check if they could solve my problem.

I would be very grateful if anybody had some input as to how to do this correctly. How can I create a pyroot object in C++ code which will be garbage collected?

Thank you very much in advance!


the TPython interface has grown organically as needs arise (I know only fewer than a handful of users). I’ve added an extra “python_owns” paramater to ObjectProxy_FromVoidPtr, which by default is false. Is in v5-34-00-patches.

I don’t know of any other (clean) way.



I just tested it, works like a charm. Thank you very much!

BTW: I really like the pyroot bindings, they made my life a lot easier and I know of a few people who think the same. I certainly hope that there are more than a few people out there appreciating this.