Get Programming: Learn To Code With Python

458 Pages·2018·15.055 MB·English

by  Ana Bell

Thinking like a programmer: big ideas
Idea Thinking like a programmer—details Section
Setting up Don’t start to code immediately. You’ll feel boxed into one path 19.1.2
that may or may not even be appropriate for the problem at
hand.
Setting up If you find yourself writing convoluted logic to achieve a simple 17.2
task or repeating yourself several times, take a step back and
use a piece of paper to draw out what you want to achieve.
Setting up When thinking about how to break down your problem, choose 29.1
tasks and write tasks in such a way that they can be reusable.
Setting up Before beginning to code, think about each data type you’ve 29.3
learned about and decide whether it’s an appropriate one to use.
When more than one may work, pick the simplest one.
Setting up When choosing data attributes to represent an object type, you 32.1.1
can (1) Write out the data types you know and ask whether each
would be appropriate to use. (2) Notice whether the behaviors
you want can be represented by one or more data structures
you already know.
Setting up Think about expressions that contain decisions as Boolean 13.1.1
expressions (which evaluate to true or false) as opposed to ques-
tions (which have yes or no answers).
Setting up Computers do only what they’re told. When writing code, the 16.1.2
computer will execute everything you write according to the rules
of the programming language.
Readability A programmer writes readable code, both for others to be able 14.2.2
to read as well as for themselves to look back on later. Use
descriptive variables to store complex computations.
Readability Don’t use variable names that are very long. They make your 4.2.3
code unreadable.
Readability Create variables to store values that you’re going to reuse many 18.3.1
times in your code.
GPPython.book Page i Monday, March 19, 2018 4:48 PM
Get Programming
Learn to code
with Python
Ana Bell
MANNING
Shelter Island
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For online information and ordering of this and other Manning books, please visit
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Manning Publications Co. Development editor: Elesha Hyde
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PO Box 761 Review editor: Aleksandar Dragosavljevic´
Shelter Island, NY 11964 Project editor: David Novak
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ISBN 9781617293788
Printed in the United States of America
1 2 3 4 5 6 7 8 9 10 – EBM – 23 22 21 20 19 18
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To my sons, James and Thomas
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Contents
Preface vii
Acknowledgments viii
About this Book ix
About the author xii
Unit 0
Lesson 8 Advanced string operations 73
LEARNING HOW TO PROGRAM Lesson 9 Simple error messages 79
Lesson 10 Tuple objects: sequences of any kind of
Lesson 1 Why should you learn how to
object 82
program? 3
Lesson 11 Interacting with the user 88
Lesson 2 Basic principles of learning a program-
ming language 10 Lesson 12 Capstone project: name mashup 96
Unit 1 Unit 3
VARIABLES, TYPES, EXPRESSIONS, AND MAKING DECISIONS IN YOUR PROGRAMS
STATEMENTS
Lesson 13 Introducing decisions in programs 107
Lesson 3 Introducing Python: a programming Lesson 14 Making more-complicated
language 25 decisions 120
Lesson 4 Variables and expressions: giving names Lesson 15 Capstone project: choose your own
and values to things 36 adventure 135
Lesson 5 Object types and statements
of code 46 Unit 4
Lesson 6 Capstone project: your first Python pro-
gram—convert hours to minutes 55
REPEATING TASKS
Unit 2 Lesson 16 Repeating tasks with loops 143
Lesson 17 Customizing loops 152
Lesson 18 Repeating tasks while conditions
STRINGS, TUPLES, AND INTERACTING WITH
hold 158
THE USER
Lesson 19 Capstone project: Scrabble, Art
Lesson 7 Introducing string objects: sequences of Edition 170
characters 65
v
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vi Contents
Unit 5 Unit 7
ORGANIZING YOUR CODE INTO REUSABLE MAKING YOUR OWN OBJECT TYPES BY
BLOCKS USING OBJECT-ORIENTED PROGRAMMING
Lesson 20 Building programs to last 183 Lesson 30 Making your own object types 297
Lesson 21 Achieving modularity and abstraction with Lesson 31 Creating a class for an object type 303
functions 194 Lesson 32 Working with your own object
Lesson 22 Advanced operations with types 313
functions 206 Lesson 33 Customizing classes 322
Lesson 23 Capstone project: analyze your Lesson 34 Capstone project: card game 330
friends 219
Unit 8
Unit 6
USING LIBRARIES TO ENHANCE YOUR
WORKING WITH MUTABLE DATA TYPES PROGRAMS
Lesson 24 Mutable and immutable objects 235 Lesson 35 Useful libraries 341
Lesson 25 Working with lists 242 Lesson 36 Testing and debugging your
Lesson 26 Advanced operations with lists 253 programs 352
Lesson 27 Dictionaries as maps between Lesson 37 A library for graphical user
objects 261 interfaces 362
Lesson 28 Aliasing and copying lists and Lesson 38 Capstone project: game of tag 371
dictionaries 273 Appendix A Answers to lesson exercises 381
Lesson 29 Capstone project: document Appendix B Python cheat sheet 427
similarity 284
Appendix C Interesting Python libraries 430
Index 433
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Preface
I wanted to write this book for two main reasons. I aimed to fill a need for a book that
truly taught programming from scratch, and that presented programming as an activity
that can help you with daily tasks.
A common misconception people have is that programing has to be a big endeavor
every time you do it, where you’re trying to write a program that can solve a world
problem. But that’s not so. Learning to program can improve your day-to-day life! I
write short programs all the time, whether it’s to solve puzzles or to help me make deci-
sions. I wanted to capture this sentiment in this book by making programming as acces-
sible to everyone as I can, showing how with even a little bit of programming
knowledge, you can write useful programs customized to your needs.
I teach an introductory Python computer science course for undergraduates. For the
most part, many students taking the class have no prior programming experience, in
any language. The course is fast-paced, and many students ask if there are any
resources online for people who have never programmed before. Almost all the
resources I point them to require prior knowledge of programming, which adds another
level of indirection to their learning: they have to first grasp the idea of programming
and then understand how to apply that to Python. I try not to forget what it’s like to
start learning to program from scratch, no matter how many times I teach the course. I
want this book to be a gentle introduction to programming in one of the most popular
languages at this time, that also shows how approachable coding can be.
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Acknowledgments
I’m so glad I had the opportunity to write this book, so I can help others who are just
starting out in the wide world of programming.
First, I’d like to thank my husband, CJ. His support throughout the writing of this book was
unwavering, from offering suggestions to watching our son while I wrote on weekends.
Next, I’d like to thank my parents and sister. My dad taught me programming when I
was 12, and I’ll never forget how many times he had to explain object-oriented pro-
gramming to me before it finally clicked. My sister and mom travelled across the coun-
try a few times a year to help watch my sons while I got more writing done. My mom,
especially, was my “secret weapon.” She has never programmed before and was the
perfect target audience, working through the exercises and reviewing the chapters as I
was writing them.
I’d also like to thank my development editors at Manning: Kristen Watterson, Dan
Maharry, and Elesha Hyde. The book underwent many transformations to become what
it is, and I thank them all for their patience while I wrote and rewrote lessons. Their sug-
gestions were much appreciated and made the book that much stronger. A big thanks
also goes to my technical development editor, Frances Buontempo, and technical proof-
reader, Ignacio Beltran Torres, who carefully read the lessons and pointed out correc-
tions and had wonderful suggestions on how to improve the book. Also thanks to
everyone else at Manning who helped produce and promote the book. Of course, thank
you to all the reviewers who offered their time to read and comment on the book at all
stages of development. They are Alexandria Webb, Ana Pop, Andru Estes, Angelo
Costa, Ariana Duncan, Artiom Plugachev, Carlie Cornell, David Heller, David Moravec,
Adnan Masood, Drew Leon, George Joseph, Gerald Mack, Grace Kacenjar, Ivo Stimac,
James Gwaltney, Jeon-Young Kang, Jim Arthur, John Lehto, Joseph M. Morgan, Juston
Lantrip, Keith Donaldson, Marci Kenneda, Matt Lemke, Mike Cuddy, Nestor Narvaez,
Nicole E. Kogan, Nigel John, Pavol Kráľ, Potito Colluccelli, Prabhuti Prakash, Randy
Coffland, R. Udendhran Mudaliyar, Rob Morrison, Rujiraporn Pitaksalee, Sam Johnson,
Shawn Bolan, Sowmy Vajjala-Balakrishna, Steven Parr, Thomas Ballinger, Tom North-
wood, Vester Thacker, Warren Rust, Yan Guo, and Yves Dorfsman.
viii