Python 2 and 3 Compatibility

Python 2 and 3 Compatibility With Six and Python-Future Libraries Joannah Nanjekye Python 2 and 3 Compatibility Joannah Nanjekye Kampala, Uganda ISBN-13 (pbk): 978-1-4842-2954-5 ISBN-13 (electronic): 978-1-4842-2955-2 https://doi.org/10.1007/978-1-4842-2955-2 Library of Congress Control Number: 2017962338 Copyright © 2017 by Joannah Nanjekye This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. Trademarked names, logos, and images may appear in this book. Rather than use a trademark symbol with every occurrence of a trademarked name, logo, or image we use the names, logos, and images only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. While the advice and information in this book are believed to be true and accurate at the date of publication, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein. Cover image designed by Freepik Managing Director: Welmoed Spahr Editorial Director: Todd Green Acquisitions Editor: Todd Green Development Editor: James Markham Technical Reviewer: Benjamin Peterson Coordinating Editor: Jill Balzano Copy Editor: Kim Burton-Weisman Compositor: SPi Global Indexer: SPi Global Artist: SPi Global Distributed to the book trade worldwide by Springer Science+Business Media New York, 233 Spring Street, 6th Floor, New York, NY 10013. Phone 1-800-SPRINGER, fax (201) 348-4505, e-mail [email protected], or visit www.springeronline.com. Apress Media, LLC is a California LLC and the sole member (owner) is Springer Science + Business Media Finance Inc (SSBM Finance Inc). SSBM Finance Inc is a Delaware corporation. For information on translations, please e-mail [email protected], or visit http://www.apress.com/ rights-permissions. Apress titles may be purchased in bulk for academic, corporate, or promotional use. eBook versions and licenses are also available for most titles. For more information, reference our Print and eBook Bulk Sales web page at http://www.apress.com/bulk-sales. Any source code or other supplementary material referenced by the author in this book is available to readers on GitHub via the book’s product page, located at www.apress.com/9781484229545. For more detailed information, please visit http://www.apress.com/source-code. Printed on acid-free paper To my family, who have always given me the support to soar; most importantly, my mother, who always reminds me that one of the best decisions I have ever made was to become an engineer. I am grateful for the all-around support (Internet, food, and everything I can’t list here because of space). To the hardworking chief forensic accountant without a CPA, Edmond Mabinda, who tracks every penny in Uganda—other than his own. Thanks for your work on this and the work you will continue doing. I’m not forgetting Phionah Bugosi, the programmer who cares more about the color of her laptop bag than her code. Thanks for your work reviewing all the code. Contents About the Author ................................................................................................... xiii About the Technical Reviewer .................................................................................xv Acknowledgments .................................................................................................xvii Introduction ............................................................................................................xix ■ Chapter 1: Printing and Backtick repr ................................................................... 1 Print �� 1 Using __future__ �� 1 Using six ��2 Task: Introducing Your Mentor �� 3 Using __future__ ��4 Using six ��5 Backtick repr �� 6 Coexistence Gotchas �� 8 Summary �� 8 ■ Chapter 2: Numbers ............................................................................................. 11 Inspecting Integers �� 11 Using Python-future’s builtins Module ��11 Using past�builtins from Python-future ��12 Using six ��12 Long Integers �� 12 Using Python-future’s builtins Module ��12 v ■ CONTENTS Floor Division �� 13 Float Division ��13 Python 2 Compatible Division (Old Division) ��13 Octal Constants ��16 Using __future__ ��16 Using six ��17 Summary �� 18 ■ Chapter 3: Setting Metaclasses ........................................................................... 21 Metaclasses at a Glance �� 21 Metaclasses: The Python 2 Way �� 22 Metaclasses in Python 3 �� 22 Metaclasses Compatibility �� 23 Using Python-future ��23 Using six ��24 Using the with_metaclass() Method ��24 Using the add_metaclass() Class Decorator ��25 Summary �� 27 ■ Chapter 4: Strings and Bytes ............................................................................... 31 Text and Binary Data �� 31 Unicode String Literals �� 32 Explicit Marking with Prefix ��32 Import unicode_literals from __future_ ��33 six to Classify the Unicode Data ��33

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