[Python-Dev] Inline and SWIG

Thomas Heller thomas.heller@ion-tof.com
Thu, 23 Aug 2001 19:49:40 +0200

From: "Greg Ewing" <greg@cosc.canterbury.ac.nz>
> David Beazley <beazley@cs.uchicago.edu>:
> > I've looked briefly at Inline and agree that it's a pretty nifty
> > approach.  However, usability aside, it's got a number of pretty major
> > limitations once you start getting into structure wrapping, C++
> > classes, and other advanced types of extension wrapping.
> Indeed, you've put your finger on what seems like the
> biggest problem with the current crop of semi-automatic
> extension generators.
> I don't think there is ever going to be a completely
> automatic solution to this, because, once you get beyond
> the basic types like ints, floats and strings, there is
> no unique mapping between Python types and C types.
> While the tool could provide some sort of default
> translation for arbitrary types, it's unlikely to be
> what you need to interface directly with some existing
> C library you're trying to wrap. So you're faced with
> writing a lot of tedious and error-prone code for messing 
> with PyObjects and reference counts.
> I've had some ideas floating around in my head for a
> while concerning what to do about this. The key
> observation is that such code usually spends a lot
> more lines manipulating Python data than it does C
> data, which leads me to the conclusion that C is the
> wrong language to write it in. 
> What's the right language? One that's good at manipulating
> Python objects. Which language is the best at doing
> that? Why, Python, of course. But not just Python,
> because we need to be able to manipulate C data
> structures as well. So we need a language that looks
> like Python at one end and C at the other...

I've written (well, it's not finished and maybe never will)
an extension allowing to create or wrap and manipulate C structures
and unions from Python. The basics are similar to an
OO-ified struct module, but the format codes are extensible.

It even handles the Microsoft TypeInfo structures, which
are full of recursions.

Makes a pretty good pair with a calldll-like extension module.