That was just my example, I do not require it to go into a numeric array. It just seemed like the way I was suppose to do it based on the documentation. As long as I can access the data in any form in python, I'll be happy. And I only need to read the data, I do not need to modify the array.
I did see your library but I was hoping to be able to do this without incorporating another library. I had hoped that there was something simple after seeing the numeric part in the documentation. -- Enrico Ng -----Original Message----- From: Jim Bosch [mailto:tallji...@gmail.com] Sent: Wednesday, January 20, 2010 8:03 PM To: cplusplus-sig@python.org Cc: Ng, Enrico Subject: Re: [C++-sig] Arrays to python On Wed, 2010-01-20 at 17:51 -0500, Ng, Enrico wrote: > I have C code similar to the following: > > float image_data[IMAGE_SIZE]; > const float *get_data() > > get_data returns a pointer to image_data. I'd like to expose get_data to > python and have it return a copy of the array in some Python type. (it is > actually a 2D array of image data) > I have to admit I'm not really familiar with using boost::python::numeric; I don't know how well it works with numeric and numarray's successor, numpy, and I pretty much use numpy exclusively (no one is supporting the other two anymore). But you can do this by using the numpy C API directly: http://docs.scipy.org/doc/numpy/reference/c-api.array.html#from-scratch and you can wrap the PyObject* you get back in a boost::python::object like so: #include <numpy/arrayobject.h> boost::python::object py_get_data() { npy_intp shape[1] = { IMAGE_SIZE }; npy_intp strides[1] = { 1 }; boost::python::handle<> array( PyArray_New(&PyArray_Type, 1, shape, NPY_FLOAT, strides, get_data(), sizeof(float), NPY_C_ARRAY_RO, NULL) ); // handle is a C++ smart pointer for PyObject* return boost::python::object(array); } It's not elegant, but it should work. It should even handle exceptions in PyArray_New properly. But you also have to do some work in the module init function (in other words, inside the BOOST_PYTHON_MODULE macro): http://docs.scipy.org/doc/numpy/reference/c-api.array.html#importing-the-api As a bit of self-promotion, I should mention I've written a fairly extensive C++ multidimensional array library that provides automatic boost::python converters to numpy, and might do what you're looking for better: http://code.google.com/p/ndarray/ Documentation for the Python stuff isn't great, but I'd be happy to answer any questions. Jim Bosch _______________________________________________ Cplusplus-sig mailing list Cplusplus-sig@python.org http://mail.python.org/mailman/listinfo/cplusplus-sig
