Wrapping a C library in Python

[Roy Smith]

loritsch at gmail.com (Michael Loritsch) wrote:
> If speed of development is your main goal, then I'd use ctypes. 
> ctypes will dynamically load the library in python code.  At the
> python code level, you should then do the translation to python types.
>  No C/C++ coding required.

OK, I decided to give ctypes a try.  After a few false steps (mostly 
related to sorting out LD_LIBRARY_PATH issues), I got it to work for 
simple functions.  Once you get your head around how it works, it's 
pretty neat.

The problem is, I'm at a loss what to do for a slightly more complex 
case.  The API I'm working with requires that you create a dm_handle 
which you then pass into all the other calls to establish a context.  
You start with (approximately):

/*
 * Create a handle.  The caller must have allocated memory for
 * the object pointed to by dmh.
 */
create_dm_handle (struct dm_handle *dmh);

I don't see how I can do the required memory allocation.  Calling 
malloc() directly seems kind of scary.  Even if I could do that, doing 
sizeof (struct dm_handle) won't work in the Python environment.

Am I missing something obvious here?