Python API : constant variables & sub module creation

[mg]

Hi everybody...

I am using Python API in order to create bindings.
So, in the init function of my module, I create constants :

PyMODINIT_FUNC initMyModule( void )
{
PyObject* module = Py_InitModule3( "MyModule", 0, "this is my
module" ) ;
if( ! module ) return ;

PyObject* dict = PyModule_GetDict( module ) ;
if( ! dict ) return ;

long value = 0 ; // for the example
PyObject* py_value = PyInt_FromLong( value ) ;
char* name = "NULL" ;
PyDict_SetItemString( dict, name, py_value ) ;
Py_DECREF( py_value ) ;
}

So, my first "problem" is that my module variable is mutable; I can
write the following instruction in python :
99

Then, my question is : how can I implement a constant variable from the
API ?

My second problem is that I would like implement my NULL variable in a
sub module of my module in order to write the follow python syntax :
0

Then, my question is : how can I do it ?

Thanks a lot,
Mathieu