myfoo.hpp

#ifndef MYFOO_HPP
#define MYFOO_HPP

#include <vector>

double sum(const std::vector<double> & a) {
  double sum = 0.0;
  for (const auto & elem: a) {
    sum += elem;
  }
  return sum;
}

#endif // MYFOO_HPP

myfoo.i

%module myfoo

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

%include <std_vector.i>
namespace std {
%template(Line) vector<double>;
}

%include "myfoo.hpp"

setup.py

from distutils.core import setup, Extension

setup(
    name='myfoo',
    ext_modules=[
        Extension(
            '_myfoo',
            ['myfoo.i'],
            swig_opts=['-keyword', '-c++'],
            extra_compile_args=['-std=c++11']
            )
        ],
    py_modules=['myfoo'],
    )