2007-05-31

python bindings generator

For the ns-3 project, I've been trying for some time to create some Python bindings. I've been using Py++, which uses gccxml to parse C++ header files and automatically generates Boost.Python code that tries to wrap it.

Py++ is really nice. Unfortunately Boost.Python isn't nearly at the same level. Boost.Python is heavily built on C++ templates. Mastering C++ templates is Hard™. Everything Boost does is practically black magic to me. While using Py++, Boost.Python has been fighting with me every step of the way, and winning too!

I decided to move away from Boost once and for all. Some of the non-boost alternatives I could find were:
  1. Python-SIP: the code generator itself is written in C++; that doesn't make any sense! I want something I can easily hack;
  2. SWIG: also made in C/C++, and in addition generates very ugly code, almost unreadable with so much macro abuse;
  3. The PyGtk code generator. I know this one very well :) Unfortunately it has some problems, the biggest of which is that it doesn't support C++ classes, while the ns-3 code I want to wrap is pure C++.
So, in the end, there really isn't any good python bindings generator tool out there. I decided to create my own. I've set myself the following goals for my forthcoming tool:
  • Must be written in pure Python, and in good pylint-checked style;
  • Must have unit tests;
  • It should have a simple python API to generate the code, other frontends (such as header file scanning) optional and layered on top of the python API;
  • Must be easily extensible to handle new types, with strong focus on correct memory management of type convertion code;
The project is called PyBindGen (yes, I'm from a school of thought that believes project names should be descriptive of their function). First pre-alpha release is ready, supporting generation of modules with only functions, and only the basic python types. However it already supports something not supported by pygtk-codegen: out/inout parameters and, consequently, multiple return values.


bzr (0.15) branch: http://telecom.inescporto.pt/~gjc/pybindgen/bzr
Releases: http://telecom.inescporto.pt/~gjc/pybindgen/releases
Launchpad (bug reporting, etc.): https://launchpad.net/pybindgen/

The project uses WAF to build; Running "./waf" should be enough to build the example. "./waf check" should be able to run the unit tests.

1 comment:

Luis FT said...

This is a challenging project but very promising as well. Hope you find the time to push it forward. You can count on me, if it's any help. Well, at least as an annoying user and bug reporter ;)