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The Definitive Guide to Jython

Python for the Java Platform

Authors:Josh Juneau, Jim Baker, Victor Ng, Leo Soto, Frank Wierzbicki
Version:.99 of 02/07/2010

Please note that only Part I contains FINAL versions for this book. The rest is being converted from MS Word to RST format, so that process may take a while. For the time being, feel free to read Part II, III, and IV drafts as they are included with this open source release.

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Inside Cover

The Definitive Guide to Jython: Python for the Java Platform

Copyright © 2010 by Josh Juneau, Jim Baker, Victor Ng, Leo Soto, Frank Wierzbicki

All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval system, without the prior written permission of the copyright owner and the publisher.

ISBN-13 (pbk): 978-1-4302-2527-0

ISBN-13 (electronic): 978-1-4302-2528-7

Printed and bound in the United States of America 9 8 7 6 5 4 3 2 1

Trademarked names may appear in this book. Rather than use a trademark symbol with every occurrence of a trademarked name, we use the names only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark.

Java™ and all Java-based marks are trademarks or registered trademarks of Sun Microsystems, Inc., in the US and other countries. Apress, Inc., is not affiliated with Sun Microsystems, Inc., and this book was written without endorsement from Sun Microsystems, Inc.

Lead Editors: Steve Anglin, Duncan Parkes

Technical Reviewers: Mark Ramm, Tobias Ivarsson

Editorial Board: Clay Andres, Steve Anglin, Mark Beckner, Ewan Buckingham, Gary Cornell, Jonathan Gennick, Jonathan Hassell, Michelle Lowman, Matthew Moodie, Duncan Parkes, Jeffrey Pepper, Frank Pohlmann, Douglas Pundick, Ben Renow-Clarke, Dominic Shakeshaft, Matt Wade, Tom Welsh

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The information in this book is distributed on an “as is” basis, without warranty. Although every precaution has been taken in the preparation of this work, neither the author(s) nor Apress shall have any liability to any person or entity with respect to any loss or damage caused or alleged to be caused directly or indirectly by the information contained in this work. This book is available online under the Creative Commons Attribution-Share Alike license (http://creativecommons.org/licenses/by-sa/3.0/). You can read the book at http://jythonbook.com or check out the source at the book project on bitbucket at http://bitbucket.org/javajuneau/jythonbook/.


I started using Python in 2003, and I fell in love with the language for a variety of reasons. The elegance of Python’s whitespace based syntax, the well conceived built in data types, and a beautiful set of library functions. Since that time, many other people have discovered or rediscovered Python. At the time of this writing, the software industry is well into a resurgence of dynamically typed languages: Ruby, PHP, and Python. It wasn’t until I attended my first PyCon in 2004 that I became aware of Jython. People were glad of the ability to run Python programs on the Java Virtual Machine (JVM), but were wistful because at the time Jython was lagging behind the native C Python (CPython) interpreter in terms of supporting recent versions of the language. Jython was maintained by a series of individual developers, but the task of staying current with CPython was really too much for any single person. In December 2005, Frank Wierzbicki took over as the lead developer for Jython, and over the next few years managed to foster a community of developers for Jython. The authors of this book are some of the members of that community. In June of 2009, the Jython community released Jython 2.5, which implemented the same language as CPython 2.5. This was a major leap forward, bringing Jython much closer to feature parity with CPython, and laying a foundation for catching up the rest of the way with CPython. Jython 2.5 is able to run many of the most popular Python packages, including Django, Pylons, and SQLAlchemy. Jython makes for a best of both worlds bridge between the elegant, expressive code of the Python world and the “enterprise ready” Java world. Developers who work in organizations where Java is already in use can now take advantage of the expressiveness and conciseness of Python by running their Python programs on Jython. Jython provides easy integration and interoperability between Python code and existing Java code. Jython also has something to offer existing Python programmers, namely access to the very rich ecosystem of the Java Virtual Machine. There is an enormous amount of Java code out in the world. There are libraries for every task imaginable, and more. Jython gives Python programmers a way to tap into these libraries, saving both development and testing time. Web applications running on Jython can also take advantage of the scalability benefits of Java web containers such as Tomcat or GlassFish. Things are looking very bright for Jython, and this book is a timely resource for people interested in taking advantage of the benefits that Jython has to offer.

Ted Leung

Back Cover Text

Front Matter


Part I: Jython Basics: Learning the Language

Part II: Using the Language - Incomplete Drafts Only (FINAL coming soon)

Part III: Developing Applications with Jython - Incomplete Drafts Only (FINAL coming soon)

Part IV: Strategy and Technique - Incomplete Drafts Only (FINAL coming soon)

Part V: Appendicies and Attribution - Incomplete Drafts Only (FINAL coming soon)