Using boost defined C++ Virtual functions from Python

Question

I am trying to replicate some C++ code with Python where the python calls C++ functions defined with boost.

My problem comes where the original C++ code refers to a Virtual function.

The virtual functions are defined with no_init eg

 class_<G4VPhysicalVolume, G4VPhysicalVolume*, boost::noncopyable>
     ("G4VPhysicalVolume", "physical volume class", no_init)
     // ---

If I try and use them from Python I get the error message that they cannot be called from python.

   <type 'exceptions.RuntimeError'>: This class cannot be instantiated from Python

ie because of the no_init definition that means no constructors.

So my question is how is one supposed to use C++ Virtual functions from Python.

I have seen https://www.boost.org/doc/libs/1_55_0/libs/python/doc/tutorial/doc/html/python/exposing.html#python.class_virtual_functions

But this seems to be about overiding virtual functions with python.

Boost is version 1.65.1 I just happened to find some doc on boost and virtual functions that referred to 1.55. I am not sure the way it deals with Virtual functions has changed.

I am trying to develop a FreeCAD workbench and whilst FreeCAD is in the process of migrating to Python 3 the version of Python used by the daily update is Python version: 2.7.15rc1.

Not sure the oxygen documentation of classes is the latest version but G4VPhysicalVolume is documented at http://www.apc.univ-paris7.fr/~franco/g4doxy/html/classG4VPhysicalVolume.html . The boost definition is as my original post.

To provided a Complete and verifiable example is not possible without requiring somebody to download and build from source both FreeCAD and Geant4

Answer 1

好的，我发现可以使用G4PVPlacment创建物理卷。