.. rst-class:: book-body

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Notes On Jython 
=======================================================================

:author: Thava Alagu thavamuni@gmail.com
:Version: 0.1
:Date:  |date|
:status: Draft

.. |date| date:: %Y %B %d

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.. |cright| replace:: Copyright (c) 2012 Thava Alagu. Some Rights Reserved. BSD License.


.. sidebar:: Contents

  .. contents:: :local:
           :depth: 3
  .. sectnum::
           :depth: 3

Overview
=========

Jython combines the power of Python's ease of programming with
Java's rich library implementation. It follow's Python's syntax
where Java library API is available.

::

  What Does Jython Do Well?

  Prototyping
  Java investigation
      >>> from java.util import Date
      >>> d = Date()
      >>> print d
      Sat Jan 08 16:26:16 CST 2005
      >>> from java.util import Random
      >>> print dir(Random)
      ['__init__', 'nextBoolean', 'nextBytes', 'nextDouble', 'nextFloat',
      'nextGaussian', 'nextInt', 'nextLong', 'seed', 'setSeed']
      >>>

  Making bean properties accessible
      >>> print Date().time
      1105500911121

  Glues together libraries already written in Java
  Excellent embedded scripting language

  Differences - Python & Jython

  Python                                   Jython

  C                                                                  
  Multi-platform                           100% Java                 
  Compiles to .pyc                         Any JVM (currently 1.1+)  
  Extend with C                            Compiles to .class        
  GIL                                      Extend with Java          
  Python Garbage Collection                Truly multi-threaded      
                                           Java garbage collection   

Controlling Module Search Path
===============================

The sys module contains the path object which specifies the list of module search directories.
To examine it's value, we must import the sys module first::

 >> import sys
 >> from pprint import pprint
 >> pprint(sys.path)

  ['',
   '/home/user/myenv/bin',
   '/home/user/myenv/local/lib/python2.7/site-packages/distribute-0.6.24-py2.7.egg',
   '/home/user/myenv/local/lib/python2.7/site-packages/pip-1.1-py2.7.egg',
   '/home/user/myenv/lib/python2.7',
   '/home/user/myenv/lib/python2.7/plat-linux2',
   '/home/user/myenv/lib/python2.7/lib-tk',
   '/home/user/myenv/lib/python2.7/lib-old',
   '/home/user/myenv/lib/python2.7/lib-dynload',
   '/usr/lib/python2.7',
   '/usr/lib/python2.7/plat-linux2',
   '/usr/lib/python2.7/lib-tk',
   '/home/user/myenv/local/lib/python2.7/site-packages',
   '/home/user/myenv/local/lib/python2.7/site-packages/IPython/extensions']

.. see http://stackoverflow.com/questions/279237/python-import-a-module-from-a-folder
.. see sys.modules

The module search path (i.e. sys.path) includes certain platform dependent 
default directories. In addition, you can control the search path by one
of the following methods:

* Set JYTHONPATH environment variable to include additional directories.
  They will be prefixed into your module search path.
  (PYTHONPATH for cpython)

* The program can dynamically modify the module search path. It can do the
  following first::

    >>> import sys
    >>> sys.path.insert(0, '/path/to/my/module')

* If you are running virtualenv, then you can  choose to place your
  module in the local site-packages directory without affecting other installations.