Development [LWN.net]

Interview with Frank Wierzbicki from the Jython project

By Forrest Cook
June 22, 2009

Jython is a version of the Python language that is written in Java while standard Python (CPython) is written in C. From the project's V2.2 web site: "Jython is an implementation of the high-level, dynamic, object-oriented language Python written in 100% Pure Java, and seamlessly integrated with the Java platform. It thus allows you to run Python on any Java platform."

We conducted an email interview with Jython developer Frank Wierzbicki.

Greetings, Could you tell us about yourself and your role with the Jython project?

I started using Jython for testing and scripting the Java code I was working on in 1999. Ever since it remained a favorite tool for me. Sometime in 2004 I started contributing patches to the Jython project until the then project lead Brian Zimmer gave me commit privileges. A few months later Brian had some new stuff in his life that was not going to leave him with enough time for Jython development. At that point I was the heaviest contributor, and he offered me the lead role.

How many team members are on the project, and what are their functions?

There are about eight active developers committing code to Jython. I don't think there are really any defined roles, developers work in those parts of the codebase that interests them. There are some areas where one developer does most of the work, but it isn't a rigid system at all.

What was the motivation behind the creation of Jython?

Jython was started by Jim Huginin in the late nineties -- Jython's repository marks his first checkin as 1997. His motivations are described in the Story of Jython.

Do any companies provide financial backing for Jython?

Sun Microsystems allows me to spend most of my time working on Jython.

What kinds of of applications would be better to write in Jython instead of C Python?

Any application that needs to access frameworks or libraries written in Java will find that Jython does a very good job in this area. Java code can be imported and used directly by Jython code.

Applications that want to access multiple cores using threads should also consider Jython. Our multi-threading story is potentially better than CPython's due to our lack of a GIL (Global Interpreter Lock). Our dictionary implementation is based on the ConcurrentHashMap from the wonderful java.util.concurrent APIs, which means that our dictionary should scale very well in the face of multiple threads. To make good use of multiple cores from CPython, you'd need to use multiple processes or drop to C code for your threading.

How does the memory usage and speed of Jython compare with C Python?

Jython requires a larger minimum memory footprint compared to CPython, but Jython uses Java's garbage collection mechanisms, which are far more sophisticated than CPython's. I don't think this has been measured, but my gut would say that we will do better for some memory intensive tasks.

Speed-wise, we perform between the same and about two times slower compared to CPython for most tasks. There are a few areas where we find that we are faster than CPython, see here for one.

As an aside, the 2.5.0 cycle focused almost exclusively on CPython compatibility. We have done very little performance work to date. Performance will be a big focus for 2.5.1 and 2.6.

Is Jython more popular with users of Linux, other types of Unix or Windows?

I don't actually know the user statistics here. I do know that most of the Jython developers work day to day on OS X. From the questions that we get on the mailing lists and IRC, I know that Linux, Unix, and Windows are well represented in our user populations.

Could you tell us about the enhancements that have been added to the recently released Jython 2.5.0?

Our primary focus for 2.5.0 was compatibility with the 2.5 version of CPython. We have made great strides in this area, supporting far more of the libraries that ship with CPython, and we have specifically worked on getting more real world frameworks working on Jython. Some of these frameworks that are working well on Jython are: Pylons 0.9.7, Django 1.0.3 and SQLAlchemy 0.6.0.

What are the plans for upcoming releases of Jython?

We plan to release a 2.5.1 fairly quickly, to round out some of the smaller bugs that we where not able to fix for the 2.5.0 release. After that we will work on 2.6, followed by a 3.x. I don't have any real timelines for these yet.

I also plan to take advantage of the really cool work being done for JDK 7 in the Da Vinci Machine project which aims to improve the support that the JVM has for dynamic languages. Using this work (much of which has already made it's way into OpenJDK) Jython will perform better with much simpler internal code.

Is there anything else you would like to share with our readers about Jython?

Jython is a great platform for Python developers that want to work in a Java environment, and a great tool for Java developers who want to access the highly productive, highly readable, and powerful Python language.

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