Thanks to PacktPub I got a chance to read an interesting book this week: Learning Cython Programming by Philip Herron (Amazon, Packt). I was curious because, as you probably noticed, after starting at my current place of work the past April, I ended up having to learn to use Python, which ended up with me writing my glucometer utilities in that language, contrarily to most of my other work, which has been done in Ruby. But that’s a topic for a different post.
First of all, I was curious about Cython; I heard the name before but never looked much into it, and when I saw the book’s title and I quickly checked what it was, my interest was definitely picked. If you haven’t looked into it either, at a quick summary it’s a code generator bridge between Python and good plain old C, wrapping the latter such that you can either make it run Python callbacks, or generate a shared object module that Python can load, and offload the computation-intensive code to a more performant language. And it looks a lot like a well-designed and well-implemented version of what I hoped to get in Ruby with Rust — no connection with Mozilla’s language with the same name.
The book is a quick starter, short and to the point, which is an approach I like. Together with the downloadable source code, it makes it a very good solution to learn Cython, and I recommend it if you’re interested. Not only it covers the obvious language itself, but it covers a wide range of use cases that show how to make good use of the options provided by Cython. It even goes on to show how to integrate it in a build system (although I have some reserves on the Autotools code in there, which I think I’ll send Philip a correction for).
I seriously wish I had Cython and this book when I was working on Hypnos, an Ultima OnLine «server emulator» for which I wanted to add Python-based scripting — other emulators at the time used either a very simple, almost basic-like scripting language, Perl or C#. This was before I tried to use Python for real, which turned me to hate its whitespace-based indentation. I did write some support for it but it was a long and tedious process, so I never finished it. Not only Cython would make that work much less tedious, but the book shows exactly how to add Python scripting capabilities to a bigger, C program using
tmux as the example.
The book does not ignore the shortcomings of Cython of course, including the (quite clumsy) handling of exceptions when crossing the foreign language barrier. While there are still a bunch of issues to be straightened out, I think the book is fairly good at setting proper expectation for Cython. If you’re interested in the language, the book looks like the perfect fit.
I grant it ought to be faster than interpreted Python, but is still has that nasty dependence on whitespace.Here’s a burning issue: does Cython have same problem we run into every time there is a new Python version? One of the biggest annoyances in Gentoo is the frequent need to run python-updater. Normal shared libraries don’t require updates to programs which link to them so long as none of the existing API’s change. The Python run-time system is not so considerate, and I really resent having to rebuild huge packages just because Python is so ill-implemented not to live happily through such upgrades.So, if Cython is more tolerable in this regard, would there be any way to get Python-using packages to use it instead?