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01_596543 ffirs.qxd 6/29/05 11:00 PM Page i Beginning Python 01_596543 ffirs.qxd 6/29/05 11:00 PM Page ii 01_596543 ffirs.qxd 6/29/05 11:00 PM Page iii Beginning Python Peter Norton, Alex Samuel, David Aitel, Eric Foster-Johnson, Leonard Richardson, Jason Diamond, Aleatha Parker, Michael Roberts 01_596543 ffirs.qxd 6/29/05 11:00 PM Page iv Beginning Python Published by Wiley Publishing, Inc. 10475 Crosspoint Boulevard Indianapolis, IN 46256 www.wiley.com Copyright © 2005 by Wiley Publishing, Inc., Indianapolis, Indiana Published simultaneously in Canada ISBN-10: 0-7645-9654-3 ISBN-13: 978-0-7645-9654-4 Manufactured in the United States of America 10 9 8 7 6 5 4 3 2 1 1B/SQ/QX/QV/IN Library of Congress Cataloging-in-Publication Data: Beginning Python / Peter Norton. p. cm. Includes bibliographical references and index. ISBN-13: 978-0-7645-9654-4 (paper/website) ISBN-10: 0-7645-9654-3 (paper/website) 1. Python (Computer program language) I. Norton, Peter, 1974- QA76.73.P98B45 2005 005.13’3--dc22 2005013968 No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600. Requests to the Publisher for permission should be addressed to the Legal Department, Wiley Publishing, Inc., 10475 Crosspoint Blvd., Indianapolis, IN 46256, (317) 572-3447, fax (317) 572-4355, or online at http://www.wiley.com/go/permissions. 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THE FACT THAT AN ORGANIZATION OR WEBSITE IS REFERRED TO IN THIS WORK AS ACITATION AND/OR A POTENTIALSOURCE OF FURTHER INFORMATION DOES NOT MEAN THAT THE AUTHOR OR THE PUBLISHER ENDORSES THE INFORMATION THE ORGANIZATION OR WEBSITE MAYPROVIDE OR RECOMMENDATIONS IT MAYMAKE. FURTHER, READERS SHOULD BE AWARE THAT INTERNET WEBSITES LISTED IN THIS WORK MAY HAVE CHANGED OR DISAPPEARED BETWEEN THEN THIS WORK WAS WRITTEN AND WHEN IT IS READ. For general information on our other products and services please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002. Trademarks:Wiley, the Wiley logo, Wrox, the Wrox logo, Programmer to Programmer, and related trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc. and/or its affiliates, in the United States and other countries, and may not be used without written permission. All other trademarks are the property of their respective owners. Wiley Publishing, Inc., is not associated with any product or vendor mentioned in this book. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. 01_596543 ffirs.qxd 6/29/05 11:00 PM Page v About the Authors Peter Norton(NY, NY)has been working with Unix and Linux for over a decade at companies large and small solving problems with Linux. An officer of the NYLinux Users Group, he can be found on the nylug-talk mailing list. Peter coauthored Professional RHEL3. He works for a very large financial company in NYC, plying his Python and open-source skills. Alex Samuel (San Diego, CA)has developed software for biology researchers and now studies high- energy physics at Caltech. Alex has worked on many GNU/Linux development tools, including GCC, and co-founded CodeSourcery LLC, a consulting firm specializing in GNU/Linux development tools. David Aitel (NY, NY)is the CEO of Immunity and a coauthor of Shellcoder’s Handbook. Eric Foster-Johnson (Minneapolis, MN)uses Python extensively with Java, and is a veteran author, most recently completing Beginning Shell Scripting. Leonard Richardson (San Francisco, CA) writes useful Python packages with silly names. Jason Diamond (CA) Jason Diamond is a software development instructor for DevelopMentor and a consultant specializing in C++, .NET, Python, and XML. He spends most of his spare time contributing to open-source projects using his favorite language, Python. Aleathea Parker (San Francisco CA) is a programmer working as a publication engineer for a major software company, coding primarily in Python and XSLT. She has a background in web applications and content management. Michael Roberts(Puerto Rico)has been programming professionally in C, Perl, and Python for long enough that Python didn’t actually exist when he started. He is the chief perpetrator of the wftk open-source workflow toolkit, and he swears that it will someday be finished, for certain values of “finished”. 01_596543 ffirs.qxd 6/29/05 11:00 PM Page vi 01_596543 ffirs.qxd 6/29/05 11:00 PM Page vii Credits Acquisitions Editor Graphics and Production Specialists Debra Williams Cauley Sean Decker Carrie Foster Development Editor Lauren Goddard Kelly D. Henthorne Denny Hager Jennifer Heleine Production Editor Amanda Spagnuolo William A. Barton Quality Control Technicians Copy Editor Leann Harney Luann Rouff Joe Niesen Carl William Pierce Production Manager Tim Tate Media Development Specialists Angela Denny Editorial Manager Kit Malone Mary Beth Wakefield Travis Silvers Vice President & Executive Group Publisher Proofreading and Indexing Richard Swadley TECHBOOKS Production Services Vice President and Publisher Joseph B. Wikert Project Coordinator Kristie Rees 01_596543 ffirs.qxd 6/29/05 11:00 PM Page viii 01_596543 ffirs.qxd 6/29/05 11:00 PM Page ix To my Claudia, for keeping me thinking straight through a crazy time. To my mom, Eunice, for bringing me food and asking if I was okay throughout. To Debra, for roping me into this. And to all of the authors, I want to thank you for making it to the finish line. Whoa! I didn’t know what I was getting you all into! —P. N. To my dad, Clarence A. Johnson, 1922–2005. —E. F-J. For my mother. —L. R. For Jilly: 1 = 2. —J. D. To Aaron, for putting up with me. —A. P. To my wife, Agnes, in revenge for her doctoral thesis. —M. R.