SWIG Python binding seems empty

Question

I have the following files for generating a Python binding to a C++ project with SWIG and CMake:

test.h

int add(int a, int b);

test.cpp

int add(int a, int b)
{
        return a+b;
}

test.i

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

CMakeLists.txt

cmake_minimum_required(VERSION 2.6)
project(swig-test)

# This is a CMake example for Python

add_library(testcpp SHARED test.cpp)

FIND_PACKAGE(SWIG REQUIRED)
INCLUDE(${SWIG_USE_FILE})

FIND_PACKAGE(PythonLibs)
INCLUDE_DIRECTORIES(${PYTHON_INCLUDE_PATH})

INCLUDE_DIRECTORIES(${CMAKE_CURRENT_SOURCE_DIR})

SET(CMAKE_SWIG_FLAGS "")

SET_SOURCE_FILES_PROPERTIES(test.i PROPERTIES CPLUSPLUS ON)
SET_SOURCE_FILES_PROPERTIES(test.i PROPERTIES SWIG_FLAGS "-includeall")
set(${CMAKE_CXX_FLAGS} "${CMAKE_CXX_FLAGS} -fPIC")
SWIG_ADD_MODULE(test python test.i)
SWIG_LINK_LIBRARIES(test testcpp)

It compiles successfully and libtestcpp.so, _test.so, and test.py are created. strings libtestcpp.so and strings _test.so both have an entry _Z3addii and import test works in Python, but there is nothing under the test namespace in Python.

I've also tried manually compiling with

swig -c++ -python test.i
g++ -c -fpic test.cpp test_wrap.cxx -I/usr/include/python2.7 -I.
g++ -shared test.o test_wrap.o -o _test.so

with the same result.

It may be useful to note that import test isn't a completely empty module; import test; dir(test) yields

['__builtin__',
 '__builtins__',
 '__doc__',
 '__file__',
 '__name__',
 '__package__',
 '_newclass',
 '_object',
 '_swig_getattr',
 '_swig_property',
 '_swig_repr',
 '_swig_setattr',
 '_swig_setattr_nondynamic',
 '_test']

and import test; help(test) has a description that it is created by SWIG.

I think you still need to add a line %include "test.h" at the end in test.i. — R Sahu
– R Sahu, Commented Nov 14, 2016 at 21:49
That is indeed correct -- I seem to have completely overlooked that! — Daniel Underwood
– Daniel Underwood, Commented Nov 14, 2016 at 23:40
I wasn't 100% sure before I commented. I converted my comment to an answer. — R Sahu
– R Sahu, Commented Nov 15, 2016 at 3:03

R Sahu · Accepted Answer · 2016-11-15 03:02:04Z

2

You need to to add a line %include "test.h" at the end in test.i

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

%include "test.h"

answered Nov 15, 2016 at 3:02

R Sahu

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