Wrapping C/C++ for Python using SWIG

Setup:

• Install SWIG

  $ sudo apt-get install swig

Steps:

1. Create C++ functions or class functions
2. Create SWIG interface functions.i

/* File: example.i */
%module example

%{
    #define SWIG_FILE_WITH_INIT
    #include "Example.hpp"
%}

%include "Example.hpp"

3. Create CMakeLists.txt files
   1. On root folder to add C++ library

   set(CMAKE_POSITION_INDEPENDENT_CODE ON) # same as -fPIC which tells GCC to generate position-independent code (PIC) suitable for use in a shared library.
   
   add_library(functions SHARED src/functions.cpp)
   target_link_libraries(${PROJECT_NAME} functions)

   2. On swig folder to setup swig

   find_package( SWIG REQUIRED )
   include( ${SWIG_USE_FILE} )

   3. On python folder to setup python, crete the swig library and install them as python packages (checkout the entire CMakeLists.txt inside /swig/python)
4. Create setup.py.in inside /swig/python to install the python package

Folder structure

├── CMakeLists.txt
├── include
│   └── functions.hpp -> functions lid
├── src
│   ├── functions.cpp -> functions lid
│   └── main.cpp -> use functions lib in C++
└── swig
    ├── CMakeLists.txt -> include swig dependencies
    ├── functions.i -> swig interface
    └── python -> include python dependencies and install new python package
        ├── CMakeLists.txt
        ├── setup.py.in -> setup file to install python package
        └── test.py -> use functions lib in Python

Build:

$ mkdir build && cd build
$ cmake ..
$ make
$ make install-python

Run:

$ python3 swig/python/test.py