PyCon 2014 Abstract

title:

Beautypeful XDress
category:

Science
duration:

30 min
description:

XDress is an automatic wrapper generator for C/C++ written in pure Python. It can generate Python bindings (via Cython) for classes, structs, functions, and certain variables types. It can also create in-memory wrappers for C++ sets, vectors, and maps. This is because it can generate custom NumPy dtypes. This talk will go over the “zen of xdress” and teach you how to generate your own wrappers.
audience:

Anyone who has to or wants to expose a C/C++ API to Python.
Python level:

Intermediate
objectives:

To teach people basic type theory concepts, that wrapping C/C++ extension modules does not have to be painful, and that the results can be very beautiful.
detailed abstract:
 

XDress is an automatic wrapper generator for C/C++ written in pure Python. Currently, xdress may generate Python bindings (via Cython) for C++ classes & functions and in-memory wrappers for C++ standard library containers (sets, vectors, maps). In the future, other tools and bindings will be supported.

The main enabling feature of xdress is a dynamic type system that was designed with the purpose of API generation in mind. This type system provides a canonical abstraction of various kinds of types: base types (int, str, float, non-templated classes), refined types (even or odd ints, strings containing the letter ‘a’), and dependent types (templates such arrays, maps, sets, vectors). This canonical form is itself hashable, being comprised only of strings, ints, and tuples.

On top of this type system, xdress provides a tool for auto-generating classes which are views into template instantiations of C++ standard library maps and sets. Additionally, this tool also creates custom numpy dtypes for any C++ type, class or struct. This allows the user to have numpy array views into C++ vectors.

Furthermore, xdress also has a tool which inspects a C++ code base and automatically generates Cython wrappers for all user-specified classes and functions. This significantly eases the burden of supporting mixed language projects.

Other powerful features include:

  • C++ template class & function support
  • Automatic docstring generation via dOxygen
  • Wrapped names may be different than source names, allowing automatic PEP-8-ification during C/C++ to Python translation
  • First class support for C via pycparser
  • Python 3 support, by popular demand!

The above code generators, however, are just the beginning. The xdress type system is flexible and powerful enough to engender a suite of other tools which take advantage of less obvious features. For example, an automatic verification & validation utility could take advantage of refinement type predicate functions to interdict parameter constraints into the API right under the users nose!

This talk will focus on xdress’s type system and its use cases. XDress is licensed under 2-clause BSD.
outline:

  • Big Idea

  • Motivation

  • What XDress Is and Is Not

  • Type System
    • Kinds of Types
    • Base Types
    • Dependent Types
    • Refined Types

  • C/C++ API Descriptions

  • C++ Class Example

  • C++ Standard Library Container Wrappers

  • NumPy Dtype Generation

  • Plugins

  • Neat Concepts for Future Work

  • Questions

additional notes:
 

The main website is http://xdress.org/

An earlier version of this talk which used an earlier version of xdress was presented to SciPy 2013. See this page for the slides and the video. http://xdress.org/other/scipy2013/index.html
additional requirements:
 

none
recording release:
 

yes