Python Power! THE COMPREHENSIVE GUIDE Q Q Q Matt Telles © 2008 Thomson Course Technology, a division of Thomson Learning Inc. All rights reserved. Publisher and General No part of this book may be reproduced or transmitted in any form or by any means, Manager, Thomson Course electronic or mechanical, including photocopying, recording, or by any information storage Technology PTR: or retrieval system without written permission from Thomson Course Technology PTR, Stacy L. Hiquet except for the inclusion of brief quotations in a review. Associate Director of The Thomson Course Technology PTR logo and related trade dress are trademarks of Marketing: Thomson Course Technology, a division of Thomson Learning Inc., and may not be used Sarah O’Donnell without written permission. Manager of Editorial Python is a trademark of the Python Software Foundation. Services: Microsoft Windows is a registered trademark of Microsoft Corporation. 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ISBN-10: 1-59863-158-6 Cover Designer: ISBN-13: 978-1-59863-158-6 Mike Tanamachi eISBN-10: 1-59863-159-4 Indexer: Library of Congress Catalog Card Number: 2006923270 Sharon Hilgenberg Printed in the United States of America Proofreader: 08 09 10 11 12 TW 10 9 8 7 6 5 4 3 2 1 Steve Honeywell Thomson Course Technology PTR, a division of Thomson Learning Inc. 25 Thomson Place Boston, MA 02210 http://www.courseptr.com This book is dedicated to the ladies in my life: Teresa, Jenny, Rachel and Sarah. Acknowledgments The author would like to acknowledge the aid of the Python community and Usenet newsgroups in finding answers to all of the questions that eluded me. A special thanks to Mike Dawson, who went well above and beyond the call of duty to help a poor programmer out with this book. Thanks, Mike, you did a great job! Also, a small note of thanks to Marta, without whom this book would never have gotten off the ground. Thank you, dear. Now get back to work. iv Q Q Q About the Author Matt Telles is a 22-year veteran of the computer wars. Having moved from the mainframe world, with his beloved DEC 1091, he is now ensconced in the PC world of Windows and Linux. A long-time C++ programmer, he has since moved on to more modern languages like C#, Python, and PHP. The high point of his career is in writing his own biography for books. v Q Q Q This page intentionally left blank TABLE }OF Contents CHAPTER 1 About Python ............................................................................................1 What Is Python? ................................................................................................................1 A Brief History of Python ................................................................................................2 Interpreters Versus Compilers .......................................................................................5 When to Use (or Not Use) an Interpreted Language .........................................8 Understanding Bytecodes ......................................................................................10 Why Use Python? ...........................................................................................................11 Object-Oriented ........................................................................................................11 Cross Platform ..........................................................................................................11 Broad User Base .......................................................................................................11 Well Supported in Third-Party Tools ...................................................................12 Good Selection of Tools Available ........................................................................12 Good Selection of Pre-built Libraries ..................................................................12 Where Is Python Used? .................................................................................................13 How Is Python Licensed? ..............................................................................................13 Where Do I Get Python? ...............................................................................................14 Installing Python ............................................................................................................14 Getting Information on Python ..................................................................................16 Python Communities .....................................................................................................17 Other Software ................................................................................................................18 And Now for Something Completely Different… ....................................................18 CHAPTER 2 Python Language Overview .................................................................19 Python Syntax .................................................................................................................20 Comments .................................................................................................................20 Indentation ...............................................................................................................20 vii Q Q Q CONTENTS Python Reserved Words ................................................................................................24 Decision Making and Iteration Keywords ..........................................................25 Debugging Keywords ..............................................................................................27 Package and Module Handling Keywords .........................................................27 Exception Handling Keywords ..............................................................................29 General Language Keywords .................................................................................31 Other Keywords ........................................................................................................32 Variable Usage ................................................................................................................34 The Continuation Variable ....................................................................................36 Watching Out for Spelling Mistakes! ..................................................................37 Predicates .........................................................................................................................38 Identifier Scope ...............................................................................................................39 Operators .........................................................................................................................42 Modulo Operator .....................................................................................................44 Exponential Operator .............................................................................................46 Logical Operators ....................................................................................................46 Comparative Operators ..........................................................................................49 Bitwise Operators ....................................................................................................51 Membership Operators and String Operators ..................................................53 Identity Operators ...................................................................................................53 In Conclusion ..................................................................................................................53 CHAPTER 3 Tools ..........................................................................................................55 IDLE ...................................................................................................................................55