Wrapping a C++ class in Python using SWIG

Question

example.h:

#ifndef EXAMPLE_H
#define EXAMPLE_H

class Math {
 public:
    int pi() const;
    void pi(int pi);
 private:
    int _pi;
};

#endif         


        

Answer 1

Thanks for your replay!

The -C++ option generated the C++ class for the wrapper. swig -c++ -v -python example.swig

I used g++ to compile the wrapper.

g++ -fPIC -c example.cpp example_wrap.cxx -I/usr/local/include/python2.6/

And the following command to buikd the shared object. Ofcourse, we need to remove the superflous includes (-I) and libraries (-L). The important flags are '-shared' and '-fPIC'.

g++ example_wrap.o example.o -L/u01/app/oracle/product/1020.full/lib  -I/usr/local/ssl/include  -L/usr/local/ssl/lib -lclntsh -lssl -lcrypto -ldl -L/usr/local/lib -L/lib64 -L/usr/local/lib/python2.6/ -lboost_system -lboost_filesystem -lboost_thread -lboost_date_time -lglog -lmodpbase64 -lpthread -ldl -lrt -shared -fPIC -o _example.so

Answer 2

There's not enough information here to be sure what's wrong, but I have two ideas for things you can try.

1. Your g++ invocation is compiling a C source file as if it were C++. This is not guaranteed to work. Try instead

   gcc -I/usr/local/include/python2.6 -fPIC -c example_wrap.c
   gcc -I/usr/local/include/python2.6 -fPIC -c example.cpp
   g++ -shared example_wrap.o example.o -o example.so
   

   (yes, srsly, only use g++ for the link)

2. If that doesn't work, compile example_wrap.c like this:

   gcc -I/usr/local/include/python2.6 -fPIC -c -save-temps example_wrap.c
   

That will fail the same way but will produce a file named example_wrap.i which is the result of preprocesing. It will be gigantic. Search that file for the function Swig_var_Math_get, and add to your question the complete text of that function (but nothing else).

Answer 3

I think the swig command should be "swig -c++ -python example.swig"