[C++-sig] question about using a python object from C++

[Ralf W. Grosse-Kunstleve]

--- Shi Sherebrin <shi at imaging.robarts.ca> wrote:
> I've spent a lot of time reading the Boost web pages, and I'm still 
> mystified.  I have a class that I built in Python.  I want to use this 
> class in C++.  From reading about Boost it seems to allow bidirectional 
> operation, but I can't find a simple (or any) example of using C++ to 
> access a Python object.  Could someone please point me in the right 
> direction?

I am confused by your "ideal" example, but maybe this is useful:

Given sandbx/matrix.py:

class matrix:

  def __init__(self, (n_rows, n_columns)):
    self.n = (n_rows, n_columns)

Attached is the code that shows how you can create a sandbx.matrix.matrix
instance in C++. This is the test:

from sandbx_boost import to_matrix
m = to_matrix.to_matrix()
assert m.n == (2,3)

Ralf

P.S.: Sorry for all the namespace stuff. It is not essential. This is just what
I have.

#include <boost/python/module.hpp>
#include <boost/python/def.hpp>
#include <boost/python/tuple.hpp>

namespace sandbx { namespace {

  boost::python::handle<>
  import_module(const char* module_name)
  {
    using namespace boost::python;
    return handle<>(PyImport_ImportModule(const_cast<char*>(module_name)));
  }

  boost::python::object
  to_matrix()
  {
    using namespace boost::python;
    object matrix_module(import_module("sandbx.matrix"));
    object matrix = matrix_module.attr("matrix");
    return matrix(make_tuple(2,3));
  }

  void init_module()
  {
    using namespace boost::python;
    def("to_matrix", to_matrix);
  }

}} // namespace sandbx::<anonymous>

BOOST_PYTHON_MODULE(to_matrix)
{
  sandbx::init_module();
}


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