Hi:
In boost.python module,in builtin_converters.hpp
# define BOOST_PYTHON_TO_INT(T)
\
BOOST_PYTHON_TO_PYTHON_BY_VALUE(signed T, PyInt_FromLong(x)) \
BOOST_PYTHON_TO_PYTHON_BY_VALUE(unsigned T, PyInt_FromLong(x))
...
# undef BOOST_TO_PYTHON_INT