Friday, November 21, 2008

Pyrex - mixing C and Python code

I have had a little optimization mania recently. After realizing that scipy.weave is ill suited for deployment on the computers of my non-programming colleagues I was looking for other options and tried the Pyrex extension. I recommend reading the Pyrex home page for details of what exactly Pyrex is. A title sentence of its home page explains it nicely:
Pyrex lets you write code that mixes Python and C data types any way you want, and compiles it into a C extension for Python.
This has the (for me) significant advantage that there is no need to install scipy and gcc on any computer that you want your code to run on (as compared to the scipy.weave model). Distributing the compiled extension file is enough.
To make Pyrex work on Windows follow these instructions (here seems to be a copy). As usual you have to change something a bit to make it work with gcc. The key step of these instructions is creation (or edit) of distutils.cfg and adding these lines into it:
compiler = mingw32
Aside from this I also use a modified python setup command:
python build-ext --inplace
It suits me better to have the compiled extension in the working directory and not in Python dir as happens with the 'install' command.
I am aware of the Cython language which has developed from Pyrex but I have not tried it. I guess I don't need to fix what ain't broken ;-) Pyrex works great for me right now.