Jython, classpath and virtualenv

I finally came around to investigate some long standing issues I have had with my Jython development environment, namely setting up the CLASSPATH.

Background

I use Jython every day to develop customizations and tools for a big, enterprise class PLM System. Working with this system involves setting up and running Virtual Machines which run a stripped-down installation of the PLM System configured for a specific customer.

I’ve set up some shared folders and some terminal sessions such that I can code using my development tools I know and love (Python, VIM and the Terminal).

To be able to test code I develop, I want the code to run on my local machine, that is, I do not want to click-test inside the VM, restart tomcat and whatnot. I just want to fire up the python REPL and get going, I want to insert some PDB breakpoints and develop in an agile fashion. Test Driven, even.

The Problem

Up until recently, found that I needed to set up the CLASSPATH using a environment variable for all the coding sessions I did. I created some wrapper scripts which deduced the correct CLASSPATH based on the currently running VM, the customer project and some further guessing.

This always felt clumsy, but worked, for the most part.

At the same time, I missed the goodness of virtualenv, which I used to love, which yelled to me something like:

$ virtualenv -p jython foo                                                                                                                                                                ] 6:43 pm
Running virtualenv with interpreter /usr/local/bin/jython
New jython executable in foo/bin/jython
ERROR: The executable foo/bin/jython is not functioning
ERROR: It thinks sys.prefix is u'/usr/local/Cellar/jython/2.5.3b1/libexec' (should be u'/Users/seletz/develop/tmp/foo')
ERROR: virtualenv is not compatible with this system or executable

Solution

Now I need to confess. I recently started looking at some IDE, because I came across the need to code some Java for a customer project. It seems to me, that coding Java w/o a IDE is a hardcore PITA, thus, is started to look at NetBeans, Eclipse and IntelliJ (stuff for another post).

While testing testing IDEs I also tried to set them up for Python and Jython development. Whatever, I found that I can have a isolated Jython environment using virtualenv and w/o manually setting the CLASSPATH.

The error virtualenv gave me is simply due to the fact that I have JYTHON_HOME set up in my default … WTF issue?

So, I just need to:

$ cd develop/tmp
$ unset JYTHON_HOME
$ virtualenv -p jython customer_1

And – lo and behold – we have a isolated Jython environment for customer_1, just like it should be.

Poking further, I noticed that the Jython registry is also local, and, so is the ‘site-packages’ directory. Google found a post about setting up the Jython CLASSPATH, and thus I created a ‘windchill.pth’ file in the ‘site-packages’ directory:

/Volumes/wt-vm-ptc/Windchill/lib/servlet.jar
/Volumes/wt-vm-ptc/Windchill/lib/CounterPart.jar
/Volumes/wt-vm-ptc/Windchill/lib/pjl.jar
/Volumes/wt-vm-ptc/Windchill/lib/scmi.jar
/Volumes/wt-vm-ptc/Windchill/lib/wnc.jar
/Volumes/wt-vm-ptc/Windchill/lib/pdml.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/WtHttpClientAddOns.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/WtJmxClientConn.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/borland.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/commons-collections.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/commons-lang.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/Gantt.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/JClass.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/log4j.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/magelang.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/pvxdriver.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/sfc.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/vecmath.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/xercesImpl.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/xmlParserAPIs.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/xpath.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/JWSUtil.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/pview.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/jviews-chart-all.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/jviews-gantt-all.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/jviews-framework-all.jar
/Volumes/wt-vm-ptc/Windchill/codebase/lib/mpxj.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/activation.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/ie.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/ie3rdpartylibs.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/ieWeb.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/install.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/mail.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/wc3rdpartylibs.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/wncWeb.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/pdmlWeb.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/pjlWeb.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/PartsLink_L10N.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/jython.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/jdom.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/dom4j-1.5.2.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/Gantt.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/jviews-chart-all.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/jviews-framework-all.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/jviews-gantt-all.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/CounterPartWeb.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/prowtWeb.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/archiveWeb.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/archiveClientWeb.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/archiveServerWeb.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/dpimplWeb.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/InstallUtil.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/dpinfraWeb.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/json_simple-1.1.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/nexiles.tools.jar
/Volumes/wt-vm-ptc/Windchill/codebase/WEB-INF/lib/nexiles.settr.jar
/Volumes/wt-vm-ptc/Tomcat/lib/catalina.jar
/Volumes/wt-vm-ptc/Windchill/codebase

Now I can just fire up the Jython interpreter like so:

$ cd develop/tmp/customer_1
$ bin/jython
Jython 2.5.3b1 (2.5:5fa0a5810b25, Feb 22 2012, 12:39:02) 
[Java HotSpot(TM) 64-Bit Server VM (Apple Inc.)] on java1.6.0_31
Type "help", "copyright", "credits" or "license" for more information.
>>> from wt.epm import EPMDocument
>>> 

For further improvement, I can now locally manage Java dependencies using jip.