Python for Kids

348 Pages·2012·11.455 MB·English

by  Jason R. Briggs

PP YY TT HH OO NN

F O R K I D S
F O R K I D S

A Playful Introduction to Programming

J a s o n R . B r i g g s

Python for Kids

P y t h o n
fo r   K i d s
A Playful Introduction
to Programming
By Jason R. Briggs
San Francisco
PYTHON FOR KIDS. Copyright © 2013 by Jason R. Briggs.
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.
First printing
16 15 14 13 12 1 2 3 4 5 6 7 8 9
ISBN-10: 1-59327-407-6
ISBN-13: 978-1-59327-407-8
Publisher: William Pollock
Production Editor: Serena Yang
Cover and Interior Design: Octopod Studios
Illustrator: Miran Lipovaca
Developmental Editor: William Pollock
Technical Reviewers: Josh Pollock and Maria Fernandez
Copyeditor: Marilyn Smith
Compositor: Serena Yang
Proofreader: Greg Teague
For information on book distributors or translations, please contact No Starch Press, Inc.
directly:
No Starch Press, Inc.
38 Ringold Street, San Francisco, CA 94103
phone: [phone]; fax: [phone]; [email protected]; http://www.nostarch.com/
Library of Congress Cataloging-in-Publication Data
A catalog record of this book is available from the Library of Congress.
No Starch Press and the No Starch Press logo are registered trademarks of No Starch
Press, Inc. Other product and company names mentioned herein may be the trademarks of
their respective owners. Rather than use a trademark symbol with every occurrence of a
trademarked name, we are using the names only in an editorial fashion and to the benefit
of the trademark owner, with no intention of infringement of the trademark.
The information in this book is distributed on an “As Is” basis, without warranty. While
every precaution has been taken in the preparation of this work, neither the author nor
No Starch Press, Inc. 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 it.
BRIef Contents
About the Author, Illustrator, and Technical Reviewers. . . . . . . . . . . . . . . xv
Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xvii
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix
Part I: Learning to Program
Chapter 1: Not All Snakes Slither. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Chapter 2: Calculations and Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Chapter 3: Strings, Lists, Tuples, and Maps. . . . . . . . . . . . . . . . . . . . . . . . .25
Chapter 4: Drawing with Turtles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Chapter 5: Asking Questions with if and else. . . . . . . . . . . . . . . . . . . . . . . .53
Chapter 6: Going Loopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
Chapter 7: Recycling Your Code with Functions and Modules . . . . . . . . . .81
Chapter 8: How to Use Classes and Objects . . . . . . . . . . . . . . . . . . . . . . . . .93
Chapter 9: Python’s Built-in Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . .109
Chapter 10: Useful Python Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129
Chapter 11: More Turtle Graphics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145
Chapter 12: Using tkinter for Better Graphics. . . . . . . . . . . . . . . . . . . . . .163
Part II: Bounce!
Chapter 13: Beginning Your First Game: Bounce!. . . . . . . . . . . . . . . . . . .193
Chapter 14: Finishing Your First Game: Bounce! . . . . . . . . . . . . . . . . . . .205
Part III : Mr. stick Man Races for the exit
Chapter 15: Creating Graphics for the Mr. Stick Man Game . . . . . . . . . .221
Chapter 16: Developing the Mr. Stick Man Game . . . . . . . . . . . . . . . . . . .233
Chapter 17: Creating Mr. Stick Man. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251
Chapter 18: Completing the Mr. Stick Man Game. . . . . . . . . . . . . . . . . . .259
Afterword: Where to Go from Here . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .285
Appendix: Python Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .307
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .313

Contents In DetAIL
About the Author, Illustrator, and
technical Reviewers xv
Acknowledgments xvii
Introduction xix
Why Python?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx
How to Learn to Code. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx
Who Should Read This Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi
What’s in This Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xxii
The Companion Website. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii
Have Fun! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii
Part I: Learning to Program
1
not All snakes slither 3
A Few Words About Language. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Installing Python . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Installing Python on Windows 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Installing Python on Mac OS X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Installing Python on Ubuntu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Once You’ve Installed Python . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Saving Your Python Programs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
What You Learned . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
2
Calculations and Variables 15
Calculating with Python. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Python Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
The Order of Operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Variables Are Like Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Using Variables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
What You Learned . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
3
strings, Lists, tuples, and Maps 25
Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Creating Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Handling Problems with Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Embedding Values in Strings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
Multiplying Strings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Lists Are More Powerful Than Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Adding Items to a List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Removing Items from a List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
List Arithmetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
Tuples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
Python Maps Won’t Help You Find Your Way . . . . . . . . . . . . . . . . . . . . . . .39
What You Learned . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
Programming Puzzles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
#1: Favorites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
#2: Counting Combatants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
#3: Greetings! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
4
Drawing with turtles 43
Using Python’s turtle Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Creating a Canvas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Moving the Turtle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
What You Learned . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
Programming Puzzles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
#1: A Rectangle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
#2: A Triangle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
#3: A Box Without Corners. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
5
Asking Questions with if and else 53
if Statements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54
A Block Is a Group of Programming Statements . . . . . . . . . . . . . . .54
Conditions Help Us Compare Things. . . . . . . . . . . . . . . . . . . . . . . . .57
if-then-else Statements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
if and elif Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
Combining Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61
Variables with No Value—None . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61
The Difference Between Strings and Numbers. . . . . . . . . . . . . . . . . . . . . . .62
What You Learned . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
viii Contents in Detail