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pythonc++numpywrapperswig

Trouble finding numpy.i

I'm wanting to wrap some c++ code in python using swig, and I need to be able to use numpy.i to convert numpy arrays to vectors.

This has been quite the frustrating process, as I haven't been able to find any useful info online as to where I actually get numpy.i from.

This is what I currently have running:

numpy 1.17.3

swig 2.0.12

python 3.7.3

Debian 4.9.2

From reading https://docs.scipy.org/doc/numpy/reference/swig.interface-file.html I'm told that numpy.i should be located in tools/swig/numpy.i, though the only place on my machine that I can find numpy.i is in a python 2.7 folder which I've upgraded from. My working version of python (3.7.3) holds no such file. 

$ locate numpy.i
/usr/lib/python2.7/dist-packages/instant/swig/numpy.i

What I've tried:

  • copying the numpy.i (as described above) into my working folder. This is at least recognized by my test.i file when I call %include "numpy.i", but it doesn't seem to allow usage of numpy.i calls.

  • Copying this code https://github.com/numpy/numpy/blob/master/tools/swig/numpy.i into a new file called numpy.i and putting that in my folder, but I get lots of errors when I try to run it.

Is there a standard way to get the proper numpy.i version? Where would I download it from, and where should I put it?

I've included some code below as reference:

test.i:

%module test
%{
    #define SWIG_FILE_WITH_INIT
    #include "test.h"
%}

%include "numpy.i"  //this doesn't seem to do anything
%init %{
import_array();
%}

%apply (int DIM1) {(char x)};  //this doesn't seem to do anything

%include "test.h"

test.h:

#include <iostream>

void char_print(char x);

test.cpp:

#include "test.h"

void char_print(char x) {
  std::cout << x << std::endl;
  return;
}

tester.py:

import test

test.char_print(5)  #nothing is printed, since this isn't converted properly to a char.

This is just a simple example, but I've tried using numpy.i in many different ways (including copying and pasting other people's code that works for them) but it consistently doesn't change anything whether I have it in my test.i file or not.

Where/how do I get numpy.i?

Solution

  • Problem: The numpy.i file I copied over from the python2.7 package isn't compatible, and the compatible version isn't included in the installation package when you go through anaconda (still not sure why they'd do that).

    Answer: Find which version of numpy you're running, then go here (https://github.com/numpy/numpy/releases) and download the numpy-[your_version].zip file, then specifically copy the numpy.i file, found in numpy-[your_version]/tools/swig/. Now paste that numpy.i into your project working directory.