Python Embedded in C++ - c++

Question

So I have a GUI program that has a great deal of "stuff" going on. I am adding a python scripting interface so someone can interact problematically with this environment. I am using boost python. So first thing I have is a new module I want to create. For simplicity right now my module just is hello world...
#include <boost/python.hpp>
char const* greet() {
return "hello, world" ;
}
BOOST_PYTHON_MODULE(cerrnimapi) {
boost::python::def( "greet", greet ) ;
}
In my system I have a class that looks like this...
Controller::Controller( ) {
Py_Initialize( ) ;
main_module = boost::python::import( "__main__" ) ;
main_namespace = main_module.attr( "__dict__" ) ;
}
void Controller::execute_script( std::string filename ) {
try {
boost::python::api::object ignored =
boost::python::exec_file( filename.c_str(), main_namespace ) ;
} catch( boost::python::error_already_set const & ) {
if (PyErr_ExceptionMatches(PyExc_ZeroDivisionError)) {
} else {
PyErr_Print();
}
}
}
Now when I go to execute the script in the GUI I get an error...
Traceback (most recent call last):
File "/home/mokon/repository/trunk/python.py", line 1, in <module>
import cerrnimapi
ImportError: No module named cerrnimapi
So of course I am building something wrong. My build system uses autotools so here are a few pieces of that build system that relate to this...
In configure.ac:
AM_PATH_PYTHON
AC_ARG_VAR([PYTHON_INCLUDE], [Include flags for python, bypassing python-config])
AC_ARG_VAR([PYTHON_CONFIG], [Path to python-config])
AS_IF([test -z "$PYTHON_INCLUDE"], [
AS_IF([test -z "$PYTHON_CONFIG"], [
AC_PATH_PROGS([PYTHON_CONFIG],
[python$PYTHON_VERSION-config python-config],
[no],
[`dirname $PYTHON`])
AS_IF([test "$PYTHON_CONFIG" = no], [AC_MSG_ERROR([cannot find python-config for $PYTHON.])])
])
AC_MSG_CHECKING([python include flags])
PYTHON_INCLUDE=`$PYTHON_CONFIG --includes`
AC_MSG_RESULT([$PYTHON_INCLUDE])
])
AC_ARG_VAR([PYTHON_LD], [Linker flags for python, bypassing python-config])
AS_IF([test -z "$PYTHON_LD"], [
AS_IF([test -z "$PYTHON_CONFIG"], [
AC_PATH_PROGS([PYTHON_CONFIG],
[python$PYTHON_VERSION-config python-config],
[no],
[`dirname $PYTHON`])
AS_IF([test "$PYTHON_CONFIG" = no], [AC_MSG_ERROR([cannot find python-config for $PYTHON.])])
])
AC_MSG_CHECKING([python linker flags])
PYTHON_LD=`$PYTHON_CONFIG --ldflags`
AC_MSG_RESULT([$PYTHON_LD])
])
In my obj/ dir Makefile.am...
pyexec_LTLIBRARIES = cerrnimapi.la
cerrnimapi_la_SOURCES = ${SRC_DIR}/lib/PythonAPI.cpp
cerrnimapi_la_LDFLAGS = -avoid-version -module $(PYTHON_LD)
cerrnimapi_la_CXXFLAGS = $(PYTHON_INCLUDE)
My makefile builds the shared lib and its in the obj folder along with my main program. This doesn't help. I have also done a make install to install the cerrnimapi lib in the python folders. This doesn't help.
I have also tried adding the PythonAPI.cpp to my main programs SOURCES but to no avail.
Any ideas? let me know what additional information would be helpful.

Answer 1

Some things to check:
Run nm over your .so file (which might be in .libs) to make sure your module init func is exported.
Make your program print out the value of sys.path (use PyRun_SimpleString) to see where it's expecting your module to turn up. If you're defining modules for your interpreter only, you probably don't want to install them in $pyexecdir.
Read the Extending Embedded Python article. You don't really need to build dynamic libraries at all, unless you're trying for a plugin architecture.
A point on style: You should try and find $PYTHON_CONFIG outside of your tests for $PYTHON_INCLUDE and $PYTHON_LD so you're not doing the AC_PATH_PROGS twice:
AM_PATH_PYTHON
AC_ARG_VAR([PYTHON_CONFIG], [Path to python-config])
AS_IF([test -z "$PYTHON_CONFIG"], [
AC_PATH_PROGS([PYTHON_CONFIG],
[python$PYTHON_VERSION-config python-config],
[no],
[`dirname $PYTHON`])
])
AC_ARG_VAR([PYTHON_INCLUDE], [Include flags for python, bypassing python-config])
AS_IF([test -z "$PYTHON_INCLUDE"], [
AC_MSG_CHECKING([python include flags])
AS_IF([test "$PYTHON_CONFIG" = no], [AC_MSG_ERROR([cannot find python-config for $PYTHON.])])
PYTHON_INCLUDE=`$PYTHON_CONFIG --includes`
AC_MSG_RESULT([$PYTHON_INCLUDE])
])
AC_ARG_VAR([PYTHON_LD], [Linker flags for python, bypassing python-config])
AS_IF([test -z "$PYTHON_LD"], [
AC_MSG_CHECKING([python linker flags])
AS_IF([test "$PYTHON_CONFIG" = no], [AC_MSG_ERROR([cannot find python-config for $PYTHON.])])
PYTHON_LD=`$PYTHON_CONFIG --ldflags`
AC_MSG_RESULT([$PYTHON_LD])
])