boost::python::numeric::array に 値を渡す。 (embedded python)

Boost python に vector を簡単に渡したいときは、次のようにする。

#include <boost/python.hpp>
#include <boost/python/numeric.hpp>
#include <boost/python/suite/indexing/vector_indexing_suite.hpp>
#include <iostream>
#include <vector>

namespace bp = boost::python;

int main()
{
  Py_Initialize();

  bp::object main = bp::import("__main__");
  bp::object namesp = main.attr("__dict__");
  bp::numeric::array::set_module_and_type("numpy", "ndarray");
  // use numpy.ndarray as numeric::array

  bp::class_<std::vector<int> > ("PyVecInt")
    .def(bp::vector_indexing_suite<std::vector<int> > () );
  // tell python how to access the vector

  std::vector<int> vec;
  for(int i=0; i<20; i++)
    vec.push_back(i);

  bp::numeric::array ary(vec); // vector -> ndarray
  ary.resize(bp::make_tuple(4, 5));

  namesp["pyary"] = ary;  // c++ binary --> python interpreter
  exec("print pyary", namesp);
  exec("print pyary.shape", namesp);
  exec("print type(pyary)", namesp);
}

すると、次のような結果が得られる.

[[  0   1   4   9  16]
 [ 25  36  49  64  81]
 [100 121 144 169 196]
 [225 256 289 324 361]]
(4, 5)
<type 'numpy.ndarray'>

等価な python code

#equivalent python code
import numpy
pyary = numpy.array(range(20))
pyary.resize(4, 5)
print pyary
print pyary.shape
print type(pyary)