The somewhat sad story here is that Jim Hugunin, its author first created Jython on top of the JVM. It was pretty impressive back then, I remember writing applets in it many, many years ago. (1998 I think?)
Jim later created IronPython and got hired by Microsoft, where he currently works. Smart guy, it's a shame that we lost him to the dark side. :)
Anyway, back to the demo. The things I liked:
- The integration with Visual Studio looks great. I loved the example where your Python code calls a C# function and the debugger can show the mixed stack trace for both languages.
- The speed is impressive. Seems to be on par with CPython, depending on the scenario. Jython doesn't even come close.
- A minor, but nifty thing is that he has tab completition for every class and function in the .NET framework.
While IronPython is under heavy development, Jython seems to be almost abandoned. A few days ago I needed to do some log analysis as part of our all-Java build system and I wanted to use Jython to implement it. It was a disappointment though. It was slooow and the last release was more than a year ago, so it is not up to speed with the latest Python features at all. Shame really. It could be a great Groovy contender.
Update: the JRuby developers working for Sun even offered their help to Jython. Nice.