ceph/src/boost/libs/python/example/numpy/fromdata.cpp

   1 // Copyright Ankit Daftery 2011-2012.
   2 // Distributed under the Boost Software License, Version 1.0.
   3 //    (See accompanying file LICENSE_1_0.txt or copy at
   4 //          http://www.boost.org/LICENSE_1_0.txt)
   5
   6 /**
   7  *  @brief An example to show how to access data using raw pointers.  This shows that you can use and
   8  *         manipulate data in either Python or C++ and have the changes reflected in both.
   9  */
  10
  11 #include <boost/python/numpy.hpp>
  12 #include <iostream>
  13
  14 namespace p = boost::python;
  15 namespace np = boost::python::numpy;
  16
  17
  18 int main(int argc, char **argv)
  19 {
  20   // Initialize the Python runtime.
  21   Py_Initialize();
  22   // Initialize NumPy
  23   np::initialize();
  24   // Create an array in C++
  25   int arr[] = {1,2,3,4} ;
  26   // Create the ndarray in Python
  27   np::ndarray py_array = np::from_data(arr, np::dtype::get_builtin<int>() , p::make_tuple(4), p::make_tuple(4), p::object());
  28   // Print the ndarray that we just created, and the source C++ array
  29   std::cout << "C++ array :" << std::endl ;
  30   for (int j=0;j<4;j++)
  31   {
  32     std::cout << arr[j] << ' ' ;
  33   }
  34   std::cout << std::endl << "Python ndarray :" << p::extract<char const *>(p::str(py_array)) << std::endl;
  35   // Change an element in the python ndarray
  36   py_array[1] = 5 ;
  37   // And see if the C++ container is changed or not
  38   std::cout << "Is the change reflected in the C++ array used to create the ndarray ? " << std::endl ;
  39   for (int j = 0;j<4 ; j++)
  40   {
  41     std::cout << arr[j] << ' ' ;
  42   }
  43   // Conversely, change it in C++
  44   arr[2] = 8 ;
  45   // And see if the changes are reflected in the Python ndarray
  46   std::cout << std::endl << "Is the change reflected in the Python ndarray ?" << std::endl << p::extract<char const *>(p::str(py_array)) << std::endl;
  47
  48 }