Manual alternative

swig -python -c++ -I. ext_gridloop.i

root=`python -c 'import sys; print sys.prefix'`
ver=`python -c 'import sys; print sys.version[:3]'`
g++ -I. -O3 -g -I$root/include/python$ver \
    -c convert.cpp gridloop.cpp ext_gridloop_wrap.cxx
g++ -shared -o _ext_gridloop.so \
     convert.o gridloop.o ext_gridloop_wrap.o