How to transfer data structure or class from Python to C/C++?

[Aaron "Castironpi" Brady]

On Oct 16, 9:10 am, Hongtian <hongtian.i... at gmail.com> wrote:
> Not exactly.
>
> In my C/C++ application, I have following function or flow:
>
> void func1(....)
> {
>     call PyFunc(struct Tdemo, struct &Tdemo1);
>
> }
>
> I mean I want to invoke Python function 'PyFunc' and transfer a data
> structure 'Tdemo' to this function. After some process in Python, I
> want it return 'Tdemo1' back to the C/C++ application.
>
> I research boost.python and think it is not a reasonable solution
> because it make the C/C++ application too complex.
>
> Thanks.

I am stumped.  Here's what I have.

/C file:

typedef struct {
    int a;
    float b;
} TypeA;

static PyObject *
methA(PyObject *self, PyObject *args) {
    TypeA a;
    TypeA b;
    PyObject* fun;
    PyObject* res;
    TypeA* pa;
    TypeA* pb;

    PyArg_ParseTuple( args, "O", &fun );
    a.a= 10;
    a.b= 20.5;
    b.a= 30;
    b.b= 40.5;
    printf( "%p %p\n", &a, &b );

    pa= &a;
    pb= &b;

    res= PyObject_CallFunction( fun, "II", &pa, &pb );
    Py_DECREF( res );

    return PyInt_FromLong( 0 );
}

/Py file:

import ng27ext

import ctypes as c
class TypeA( c.Structure ):
    _fields_= [
        ( 'a', c.c_int ),
        ( 'b', c.c_float )
        ]

def exposed( obj1, obj2 ):
    print 'in exposed'
    print hex( obj1 ), hex( obj2 )
    a= c.POINTER( TypeA ).from_address( obj1 )
    print a
    print a.contents

print ng27ext.methA( exposed )

/Output:

0021FD48 0021FD40
in exposed
0x21fd48 0x21fd40
<ctypes.LP_TypeA object at 0x009FF350>
<__main__.TypeA object at 0x009FF4E0>
0

Which is unexpected.  The address on line 4 should be the contents of
'obj1', 0x21fd48, which it's not.  I must not be using 'from_address'
properly.