Mahesh Venkitachalam - Python Playground

Geeky Projects for the Curious Programmer

Mahesh Venkitachalam

San Francisco

PYTHON PLAYGROUND. Copyright 2016 by Mahesh Venkitachalam.

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

19 18 17 16 15 1 2 3 4 5 6 7 8 9

ISBN-10: 1-59327-604-4

ISBN-13: 978-1-59327-604-1

Publisher: William Pollock

Production Editor: Serena Yang

Cover Illustration: Josh Ellingson

Interior Design: Octopod Studios

Developmental Editor: William Pollock

Technical Reviewers: Nicholas Kramer and Raviprakash Jayaraman

Copyeditor: Kim Wimpsett

Compositor: Kathleen Miller

Proofreader: Paula L. Fleming

was created by Fred Hsu (March 2005) and has been reproduced under the Creative Commons Attribution-Share Alike 3.0 Unported license.

For information on distribution, translations, or bulk sales, please contact No Starch Press, Inc. directly:

No Starch Press, Inc.

245 8th Street, San Francisco, CA 94103

phone: 415.863.9900;

www.nostarch.com

Library of Congress Cataloging-in-Publication Data

Venkitachalam, Mahesh.

Python playground : geeky projects for the curious programmer / by Mahesh Venkitachalam.

pages cm

Includes index.

ISBN 978-1-59327-604-1 -- ISBN 1-59327-604-4

1. Python (Computer program language) 2. Electronic apparatus and appliances--Automatic control. 3. Arduino (Programmable controller)--Programming. 4. Raspberry Pi (Computer)--Programming. I. Title.

QA76.73.P98.V46 2015

005.13'3--dc23

2014046103

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.

For my parents,
A.V. Venkitachalam and N. Saraswathy,
for giving me the greatest gift of all
an education

&

For Hema
H = M2A

1
PARSING ITUNES PLAYLISTS

2
SPIROGRAPHS

3
CONWAYS GAME OF LIFE

4
GENERATING MUSICAL OVERTONES WITH THE KARPLUS-STRONG ALGORITHM

5
BOIDS: SIMULATING A FLOCK

6
ASCII ART

7
PHOTOMOSAICS

8
AUTOSTEREOGRAMS

9
UNDERSTANDING OPENGL

10
PARTICLE SYSTEMS

11
VOLUME RENDERING

12
INTRODUCTION TO THE ARDUINO

13
LASER AUDIO DISPLAY

14
A RASPBERRY PIBASED WEATHER MONITOR

A
SOFTWARE INSTALLATION

B
BASIC PRACTICAL ELECTRONICS

C
RASPBERRY PI TIPS AND TRICKS

Writing a book is like running a marathon. Or so Ive been told. But what I do know is that writing this book tested the limits of my endurance, and I couldnt have done it without my personal cheerleading squad of close friends and family.

First of all, Id like to thank my wife Hema for her constant love, encouragement, and patience throughout the two years it took to complete this work. I thank my friend Raviprakash Jayaraman for being a co-conspirator in all my dubious projects, for being a technical reviewer for this book, and for interesting lunches, movies, and trips to the S.P. Road Zoo. I thank my friend Seby Kallarakkal for pushing me to pursue this book and for all the interesting discussions we had together. I am grateful to my pal Dr. Santosh Hemachandra for helpful discussions on fast Fourier transforms. Id like to thank Karthikeyan Chellappa for helping me test out the installation of Python modules and for our running sessions around Kaikondrahalli Lake. I would also like to thank Matthew Denham (with whom I conversed on reddit) for his help on the mathematics of Spirographs.

Id like to thank Tyler Ortman and Bill Pollock of No Starch Press, for accepting my book proposal, and Serena Yang, for her professional work in editing the book. Id like to thank Nicholas Kramer for his technical review of the book.

I thank my parents A.V. Venkitachalam and N. Saraswathy for providing me with an education far beyond their financial means. Finally, I thank all my teachers who inspired me. I hope to remain a student all my life.

Welcome to Python Playground! Within these pages, youll find 14 exciting projects designed to encourage you to explore the world of programming with Python. The projects cover a wide range of topics, such as drawing Spirograph-like patterns, creating ASCII art, 3D rendering, and projecting laser patterns in sync with music. In addition to being fun in and of themselves, these projects are designed to be jumping-off points for you to explore your own ideas by expanding on each of the projects.

Python Playground is written for anyone curious about how to use programming to understand and explore ideas. The projects in this book assume that you know basic Python syntax and basic programming concepts and that youre familiar with high-school level mathematics. Ive done my best to explain in detail the math you need for all projects.

This book is not intended to be your first book on Python. I wont walk you through the basics. I will, however, show you how to use Python to solve a variety of real-world problems in a series of nontrivial projects. As you work through the projects, youll explore the nuances of the Python programming language and learn how to work with some popular Python libraries. But perhaps even more importantly, youll learn how to break down a problem into parts, develop an algorithm to solve that problem, and then implement a solution from the ground up using Python. It can be difficult to solve real-world problems because they are often open-ended and require expertise in various domains. But Python offers the tools to facilitate problemsolving. Overcoming difficulties and finding solutions to real problems is the most important part of your journey on the way to becoming an expert programmer.

Lets take a quick tour through the chapters in this book.

, we use parametric equations and Turtle graphics to draw curves like the ones generated by a Spirograph.