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Python Crash Course

Python Crash Course

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A Hands-On, Project-Based Introduction to Programming

by Eric Matthes

Brief Contents

Part I: Basics
Getting Started
Variables and Simple Data Types
Introducing Lists
Working with Lists
if Statements
Dictionaries
User Input and while Loops
Functions
Classes 
Files and Exceptions
Testing Your Code
Part II: Projects
Project 1: Alien Invasion
A Ship That Fires Bullets
Aliens! 
Scoring
Project 2: Data Visualization
Generating Data
Downloading Data
Working with APIs 
Project 3: Web Applications
Getting Started with Django
User Accounts
Styling and Deploying an App
Afterword
Appendix A: Installing Python
Appendix B: Text Editors
Appendix C: Getting Help
Appendix D: Using Git for Version Control 

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Book Details
 Price
 3.00
 Pages
 562 p
 File Size 
 5,510 KB
 File Type
 PDF format
 ISBN-10
 ISBN-13
 1-59327-603-6
 978-1-59327-603-4
 Copyright©   
 2016 by Eric Matthes

About the Author
Eric Matthes is a high school science and math teacher living in Alaska,
where he teaches an introductory Python course. He has been writing
programs since he was five years old. Eric currently focuses on writing software
that addresses inefficiencies in education and brings the benefits of
open source software to the field of education. In his spare time he enjoys
climbing mountains and spending time with his family.

About the Technical Reviewer
Kenneth Love has been a Python programmer and teacher for many years.
He has given talks and tutorials at conferences, done professional trainings,
been a Python and Django freelancer, and now teaches for an online
education company. Kenneth is also the co-creator of the django-braces
package, which provides several handy mixins for Django’s class-based
views. You can keep up with him on Twitter at @kennethlove.

Introduction
Every programmer has a story about
how they learned to write their first program.
I started learning as a child when
my father was working for Digital Equipment
Corporation, one of the pioneering companies of the
modern computing era. I wrote my first program on a
kit computer my dad had assembled in our basement. The computer consisted
of nothing more than a bare motherboard connected to a keyboard
without a case, and it had a bare cathode ray tube for a monitor. My initial
program was a simple number guessing game, which looked something
like this:
I'm thinking of a number! Try to guess the number I'm thinking of: 25
Too low! Guess again: 50
Too high! Guess again: 42
That's it! Would you like to play again? (yes/no) no
Thanks for playing!

I’ll always remember how satisfied I felt watching my family play a game
that I created and that worked as I intended it to.
That early experience had a lasting impact. There is real satisfaction
in building something with a purpose, something that solves a problem.
The software I write now meets a more significant need than my childhood
efforts, but the sense of satisfaction I get from creating a program that works
is still largely the same.

Table of Contents
Acknowledgments xxvii
Introduction xxix
Who Is This Book For? . xxx
What Can You Expect to Learn? . xxx
Why Python? xxxi
Part I: Basics 1
1 Getting Started 3
Setting Up Your Programming Environment . . 3
Python 2 and Python 3 4
Running Snippets of Python Code . 4
Hello World! . 4
Python on Different Operating Systems . 5
Python on Linux 5
Python on OS X . 8
Python on Windows . 10
Troubleshooting Installation Issues . 15
Running Python Programs from a Terminal 16
On Linux and OS X 16
On Windows 16
Exercise 1-1: python.org  . . 17
Exercise 1-2: Hello World Typos . . 17
Exercise 1-3: Infinite Skills  . . . 17
Summary . 17
2 Variables and Simple Data Types 19
What Really Happens When You Run hello_world.py 19
Variables . 20
Naming and Using Variables 21
Avoiding Name Errors When Using Variables . 21
Exercise 2-1: Simple Message . . . 23
Exercise 2-2: Simple Messages . . . . 23
Strings . 23
Changing Case in a String with Methods 24
Combining or Concatenating Strings 25
Adding Whitespace to Strings with Tabs or Newlines . 26
Stripping Whitespace . 26
Avoiding Syntax Errors with Strings 28
Printing in Python 2 29
Exercise 2-3: Personal Message  . . . . . 29
Exercise 2-4: Name Cases  . . . . 29
Exercise 2-5: Famous Quote . . . . 29
Exercise 2-6: Famous Quote 2 . . . 29
Exercise 2-7: Stripping Names . . . 29
Numbers 30
Integers . 30
Floats . 30
Avoiding Type Errors with the str() Function . 31
Integers in Python 2 32
Exercise 2-8: Number Eight  . . . 33
Exercise 2-9: Favorite Number . . . . 33
Comments 33
How Do You Write Comments? . 33
What Kind of Comments Should You Write? . 33
Exercise 2-10: Adding Comments  . . . . 34
The Zen of Python . 34
Exercise 2-11: Zen of Python  . . . 36
Summary . 36
Introducing Lists 37
What Is a List? 37
Accessing Elements in a List . 38
Index Positions Start at 0, Not 1  . . 39
Using Individual Values from a List . 39
Exercise 3-1: Names . . . . 40
Exercise 3-2: Greetings  . . . 40
Exercise 3-3: Your Own List . . . 40
Changing, Adding, and Removing Elements . 40
Modifying Elements in a List 40
Adding Elements to a List 41
Removing Elements from a List . 42
Exercise 3-4: Guest List . . . . 46
Exercise 3-5: Changing Guest List  . . 46
Exercise 3-6: More Guests   . . 46
Exercise 3-7: Shrinking Guest List  . . . 47
Organizing a List 47
Sorting a List Permanently with the sort() Method 47
Sorting a List Temporarily with the sorted() Function 48
Printing a List in Reverse Order 49
Finding the Length of a List 49
Exercise 3-8: Seeing the World  . 50
Exercise 3-9: Dinner Guests  . . 50
Exercise 3-10: Every Function   . . 50
Avoiding Index Errors When Working with Lists 50
Exercise 3-11: Intentional Error . . . 52
Summary . 52
4 Working with Lists 53
Looping Through an Entire List 53
A Closer Look at Looping 54
Doing More Work Within a for Loop 55
Doing Something After a for Loop 56
Avoiding Indentation Errors 57
Forgetting to Indent 57
Forgetting to Indent Additional Lines . 58
Indenting Unnecessarily 59
Indenting Unnecessarily After the Loop 59
Forgetting the Colon . 60
Exercise 4-1: Pizzas  . . 60
Exercise 4-2: Animals  . . . 60
Making Numerical Lists 61
Using the range() Function . 61
Using range() to Make a List of Numbers 62
Simple Statistics with a List of Numbers . 63
List Comprehensions . 63
Exercise 4-3: Counting to Twenty  . . 64
Exercise 4-4: One Million  . . . 64
Exercise 4-5: Summing a Million  . . 64
Exercise 4-6: Odd Numbers . . . . 64
Exercise 4-7: Threes  . . 64
Exercise 4-8: Cubes  . . 64
Exercise 4-9: Cube Comprehension  . . . 64
Working with Part of a List . 65
Slicing a List 65
Looping Through a Slice . 66
Copying a List . 67
Exercise 4-10: Slices  . . . . 69
Exercise 4-11: My Pizzas, Your Pizzas . . 69
Exercise 4-12: More Loops   . . . 69
Tuples 69
Defining a Tuple 69
Looping Through All Values in a Tuple 70
Writing over a Tuple 71
Exercise 4-13: Buffet  . . . 71
Styling Your Code . 72
The Style Guide . 72
Indentation 72
Line Length 73
Blank Lines 73
Other Style Guidelines 73
Exercise 4-14: PEP 8  . . . . 74
Exercise 4-15: Code Review . . . . 74
Summary . 74
5 if Statements 75
A Simple Example . 76
Conditional Tests . 76
Checking for Equality . 76
Ignoring Case When Checking for Equality . 77
Checking for Inequality . 78
Numerical Comparisons . 78
Checking Multiple Conditions 79
Checking Whether a Value Is in a List . 80
Checking Whether a Value Is Not in a List 81
Boolean Expressions . 81
Exercise 5-1: Conditional Tests . . . . 82
Exercise 5-2: More Conditional Tests   . . . 82
if Statements . 82
Simple if Statements . 82
if-else Statements 83
The if-elif-else Chain . 84
Using Multiple elif Blocks 86
Omitting the else Block . 86
Testing Multiple Conditions 87
Exercise 5-3: Alien Colors #1 . . . 88
Exercise 5-4: Alien Colors #2  . . . 88
Exercise 5-5: Alien Colors #3 . . . 89
Exercise 5-6: Stages of Life  . . . 89
Exercise 5-7: Favorite Fruit   . 89
Using if Statements with Lists . 89
Checking for Special Items 90
Checking That a List Is Not Empty . . . 91
Using Multiple Lists . 92
Exercise 5-8: Hello Admin . . 93
Exercise 5-9: No Users . . . 93
Exercise 5-10: Checking Usernames   . . . 93
Exercise 5-11: Ordinal Numbers . . . . 93
Styling Your if Statements . 94
Exercise 5-12: Styling if statements   . . 94
Exercise 5-13: Your Ideas  . . . 94
Summary . 94
6 Dictionaries 95
A Simple Dictionary 96
Working with Dictionaries 96
Accessing Values in a Dictionary . 97
Adding New Key-Value Pairs . 97
Starting with an Empty Dictionary  . . . . 98
Modifying Values in a Dictionary 99
Removing Key-Value Pairs . 100
A Dictionary of Similar Objects 100
Exercise 6-1: Person  . . . 102
Exercise 6-2: Favorite Numbers  . . . 102
Exercise 6-3: Glossary . . . 102
Looping Through a Dictionary . 102
Looping Through All Key-Value Pairs . . . . 103
Looping Through All the Keys in a Dictionary . 104
Looping Through a Dictionary’s Keys in Order . 106
Looping Through All Values in a Dictionary . 107
Exercise 6-4: Glossary 2 . . . 108
Exercise 6-5: Rivers  . . . 108
Exercise 6-6: Polling . . . . 108
Nesting 109
A List of Dictionaries . 109
A List in a Dictionary 111
A Dictionary in a Dictionary 113
Exercise 6-7: People  . . 114
Exercise 6-8: Pets  . . 115
Exercise 6-9: Favorite Places  . . . . 115
Exercise 6-10: Favorite Numbers  . . . . 115
Exercise 6-11: Cities . . . . 115
Exercise 6-12: Extensions  . . 115
Summary . 115
7 User Input and while Loops 117
How the input() Function Works 118
Writing Clear Prompts 118
Using int() to Accept Numerical Input 119
The Modulo Operator . 120
Accepting Input in Python 2.7 121
Exercise 7-1: Rental Car  . . . 121
Exercise 7-2: Restaurant Seating  . . 121
Exercise 7-3: Multiples of Ten  . . 121
Introducing while Loops . 122
The while Loop in Action . 122
Letting the User Choose When to Quit 122
Using a Flag 124
Using break to Exit a Loop 125
Using continue in a Loop . 126
Avoiding Infinite Loops . 126
Exercise 7-4: Pizza Toppings   . . 127
Exercise 7-5: Movie Tickets . . . . 127
Exercise 7-6: Three Exits  . . . 128
Exercise 7-7: Infinity  . . . 128
Using a while Loop with Lists and Dictionaries 128
Moving Items from One List to Another 128
Removing All Instances of Specific Values from a List 129
Filling a Dictionary with User Input . 130
Exercise 7-8: Deli  . . . . 131
Exercise 7-9: No Pastrami   . . . 131
Exercise 7-10: Dream Vacation  . . . 131
Summary . 131
8 Functions 133
Defining a Function . 134
Passing Information to a Function . 134
Arguments and Parameters 135
Exercise 8-1: Message  . . 135
Exercise 8-2: Favorite Book  . . . . 135
Passing Arguments 135
Positional Arguments 136
Keyword Arguments . 137
Default Values . 138
Equivalent Function Calls . . . 139
Avoiding Argument Errors . 140
Exercise 8-3: T-Shirt   . . . 141
Exercise 8-4: Large Shirts . . . . 141
Exercise 8-5: Cities . . 141
Return Values 141
Returning a Simple Value 142
Making an Argument Optional 142
Returning a Dictionary 144
Using a Function with a while Loop 145
Exercise 8-6: City Names  . . . 146
Exercise 8-7: Album . . . 146
Exercise 8-8: User Albums . . . 146
Passing a List 147
Modifying a List in a Function 147
Preventing a Function from Modifying a List . 149
Exercise 8-9: Magicians  . . . 150
Exercise 8-10: Great Magicians . . . 150
Exercise 8-11: Unchanged Magicians   . . 150
Passing an Arbitrary Number of Arguments 151
Mixing Positional and Arbitrary Arguments . 152
Using Arbitrary Keyword Arguments . 152
Exercise 8-12: Sandwiches  . . 154
Exercise 8-13: User Profile . . . 154
Exercise 8-14: Cars  . . 154
Storing Your Functions in Modules . 154
Importing an Entire Module . 154
Importing Specific Functions 156
Using as to Give a Function an Alias 156
Using as to Give a Module an Alias . 157
Importing All Functions in a Module . 157
Styling Functions . 158
Exercise 8-15: Printing Models . . 159
Exercise 8-16: Imports  . . 159
Exercise 8-17: Styling Functions   . . . 159
Summary . 159
9 Classes 161
Creating and Using a Class 162
Creating the Dog Class . 162
Making an Instance from a Class . 164
Exercise 9-1: Restaurant  . . 166
Exercise 9-2: Three Restaurants  . . . 166
Exercise 9-3: Users  . . 166
Working with Classes and Instances 167
The Car Class 167
Setting a Default Value for an Attribute . 168
Modifying Attribute Values 168
Exercise 9-4: Number Served  . . . . . 171
Exercise 9-5: Login Attempts  . . 171
Inheritance . 172
The __init__() Method for a Child Class . 172
Inheritance in Python 2.7 173
Defining Attributes and Methods for the Child Class . 174
Overriding Methods from the Parent Class 175
Instances as Attributes . 175
Modeling Real-World Objects . 177
Exercise 9-6: Ice Cream Stand  . . . 178
Exercise 9-7: Admin   . . 178
Exercise 9-8: Privileges  . . . 178
Exercise 9-9: Battery Upgrade . . . . 178
Importing Classes 179
Importing a Single Class . 179
Storing Multiple Classes in a Module 180
Importing Multiple Classes from a Module . 181
Importing an Entire Module . 182
Importing All Classes from a Module 182
Importing a Module into a Module . 183
Finding Your Own Workflow . 184
Exercise 9-10: Imported Restaurant   . 184
Exercise 9-11: Imported Admin  . . . . 184
Exercise 9-12: Multiple Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
The Python Standard Library . 184
Exercise 9-13: OrderedDict Rewrite . . . . 186
Exercise 9-14: Dice . . . 186
Exercise 9-15: Python Module of the Week . . . 186
Styling Classes 186
Summary . 187
10 Files and Exceptions 189
Reading from a File . 190
Reading an Entire File . 190
File Paths 191
Reading Line by Line 193
Making a List of Lines from a File . 194
Working with a File’s Contents 194
Large Files: One Million Digits . 195
Is Your Birthday Contained in Pi? . 196
Exercise 10-1: Learning Python . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
Exercise 10-2: Learning C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
Writing to a File 197
Writing to an Empty File . 197
Writing Multiple Lines . 198
Appending to a File 199
Exercise 10-3: Guest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
Exercise 10-4: Guest Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
Exercise 10-5: Programming Poll . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
Exceptions 200
Handling the ZeroDivisionError Exception . 200
Using try-except Blocks . 200
Using Exceptions to Prevent Crashes . 201
The else Block 202
Handling the FileNotFoundError Exception 203
Analyzing Text . 204
Working with Multiple Files . 205
Failing Silently . 206
Deciding Which Errors to Report 207
Exercise 10-6: Addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
Exercise 10-7: Addition Calculator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
Exercise 10-8: Cats and Dogs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
Exercise 10-9: Silent Cats and Dogs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
Exercise 10-10: Common Words . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
Storing Data . 208
Using json.dump() and json.load() 209
Saving and Reading User-Generated Data 210
Refactoring 212
Exercise 10-11: Favorite Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
Exercise 10-12: Favorite Number Remembered . . . . . . . . . . . . . . . . . . . . . . 214
Exercise 10-13: Verify User . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
Summary . 214
11 Testing Your Code 215
Testing a Function . 216
Unit Tests and Test Cases 217
A Passing Test . 217
A Failing Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
Responding to a Failed Test . 219
Adding New Tests 221
Exercise 11-1: City, Country . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
Exercise 11-2: Population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
Testing a Class . 222
A Variety of Assert Methods 222
A Class to Test . 223
Testing the AnonymousSurvey Class . 225
The setUp() Method 227
Exercise 11-3: Employee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
Summary . 228
Part II: Projects 231
Project 1: Alien Invasion
12 A Ship that Fires Bullets 235
Planning Your Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
Installing Pygame 236
Installing Python Packages with pip 237
Installing Pygame on Linux 238
Installing Pygame on OS X 239
Installing Pygame on Windows 240
Starting the Game Project 240
Creating a Pygame Window and Responding to User Input 241
Setting the Background Color 242
Creating a Settings Class 243
Adding the Ship Image 244
Creating the Ship Class 245
Drawing the Ship to the Screen 246
Refactoring: the game_functions Module 247
The check_events() Function . 247
The update_screen() Function . 248
Exercise 12-1: Blue Sky . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
Exercise 12-2: Game Character . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
Piloting the Ship 249
Responding to a Keypress . 249
Allowing Continuous Movement . 250
Moving Both Left and Right 252
Adjusting the Ship’s Speed 253
Limiting the Ship’s Range 255
Refactoring check_events() 255
A Quick Recap . 256
alien_invasion.py . 256
settings.py . 256
game_functions.py . 256
ship.py . 257
Exercise 12-3: Rocket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
Exercise 12-4: Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
Shooting Bullets 257
Adding the Bullet Settings 257
Creating the Bullet Class . 258
Storing Bullets in a Group . 259
Firing Bullets 260
Deleting Old Bullets 261
Limiting the Number of Bullets 262
Creating the update_bullets() Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
Creating the fire_bullet() Function . 264
Exercise 12-5: Sideways Shooter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
Summary . 264
13 Aliens! 265
Reviewing Your Project . 266
Creating the First Alien 266
Creating the Alien Class . 267
Creating an Instance of the Alien . 268
Making the Alien Appear Onscreen . 268
Building the Alien Fleet 269
Determining How Many Aliens Fit in a Row . 269
Creating Rows of Aliens 270
Creating the Fleet . 271
Refactoring create_fleet() . 273
Adding Rows . 273
Exercise 13-1: Stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
Exercise 13-2: Better Stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
Making the Fleet Move 276
Moving the Aliens Right 276
Creating Settings for Fleet Direction 277
Checking to See Whether an Alien Has Hit the Edge 278
Dropping the Fleet and Changing Direction . 278
Exercise 13-3: Raindrops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
Exercise 13-4: Steady Rain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
Shooting Aliens . 280
Detecting Bullet Collisions 280
Making Larger Bullets for Testing 281
Repopulating the Fleet 282
Speeding Up the Bullets 283
Refactoring update_bullets() . 283
Exercise 13-5: Catch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
Ending the Game 284
Detecting Alien-Ship Collisions . 284
Responding to Alien-Ship Collisions 285
Aliens that Reach the Bottom of the Screen 288
Game Over! 288
Identifying When Parts of the Game Should Run . 289
Exercise 13-6: Game Over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
Summary . 290
14 Scoring 291
Adding the Play Button 292
Creating a Button Class 292
Drawing the Button to the Screen . 294
Starting the Game 295
Resetting the Game 296
Deactivating the Play Button 297
Hiding the Mouse Cursor 298
Exercise 14-1: Press P to Play . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
Exercise 14-2: Target Practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
Leveling Up 299
Modifying the Speed Settings 299
Resetting the Speed 300
Exercise 14-3: Challenging Target Practice . . . . . . . . . . . . . . . . . . . . . . . . . 301
Scoring 301
Displaying the Score . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
Making a Scoreboard 303
Updating the Score as Aliens Are Shot Down 304
Making Sure to Score All Hits 305
Increasing Point Values . 306
Rounding the Score 307
High Scores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
Displaying the Level 310
Displaying the Number of Ships . 313
Exercise 14-4: All-Time High Score . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
Exercise 14-5: Refactoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
Exercise 14-6: Expanding Alien Invasion . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
Summary . 317
Project 2: Data Visualization
15
Generating Data 321
Installing matplotlib . 322
On Linux . 322
On OS X . 322
On Windows 323
Testing matplotlib . 323
The matplotlib Gallery 323
Plotting a Simple Line Graph 324
Changing the Label Type and Graph Thickness . 324
Correcting the Plot 326
Plotting and Styling Individual Points with scatter() 326
Plotting a Series of Points with scatter() 328
Calculating Data Automatically 328
Removing Outlines from Data Points . 329
Defining Custom Colors 330
Using a Colormap 330
Saving Your Plots Automatically . 331
Exercise 15-1: Cubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
Exercise 15-2: Colored Cubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
Random Walks . 331
Creating the RandomWalk() Class 332
Choosing Directions . 332
Plotting the Random Walk . 333
Generating Multiple Random Walks . 334
Styling the Walk 335
Coloring the Points . 335
Plotting the Starting and Ending Points 336
Cleaning Up the Axes . 337
Adding Plot Points 337
Altering the Size to Fill the Screen 338
Exercise 15-3: Molecular Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
Exercise 15-4: Modified Random Walks . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
Exercise 15-5: Refactoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
Rolling Dice with Pygal 339
Installing Pygal 340
The Pygal Gallery 340
Creating the Die Class 340
Rolling the Die . 341
Analyzing the Results 341
Making a Histogram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
Rolling Two Dice 343
Rolling Dice of Different Sizes 345
Exercise 15-6: Automatic Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
Exercise 15-7: Two D8s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
Exercise 15-8: Three Dice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
Exercise 15-9: Multiplication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
Exercise 15-10: Practicing with Both Libraries . . . . . . . . . . . . . . . . . . . . . . . 346
Summary . 347
16 Downloading Data 349
The CSV File Format 350
Parsing the CSV File Headers 350
Printing the Headers and Their Positions 351
Extracting and Reading Data . 352
Plotting Data in a Temperature Chart 353
The datetime Module 354
Plotting Dates 355
Plotting a Longer Timeframe 356
Plotting a Second Data Series 357
Shading an Area in the Chart 358
Error-Checking . 359
Exercise 16-1: San Francisco . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
Exercise 16-2: Sitka-Death Valley Comparison . . . . . . . . . . . . . . . . . . . . . . . 362
Exercise 16-3: Rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
Exercise 16-4: Explore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
Mapping Global Data Sets: JSON Format 362
Downloading World Population Data . 362
Extracting Relevant Data . 363
Converting Strings into Numerical Values 364
Obtaining Two-Digit Country Codes . 365
Building a World Map 367
Plotting Numerical Data on a World Map . 368
Plotting a Complete Population Map 369
Grouping Countries by Population 371
Styling World Maps in Pygal . 372
Lightening the Color Theme . 374
Exercise 16-5: All Countries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
Exercise 16-6: Gross Domestic Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
Exercise 16-7: Choose Your Own Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
Exercise 16-8: Testing the country_codes Module . . . . . . . . . . . . . . . . . . . . . 375
Summary . 375
17 Working with APIs 377
Using a Web API 378
Git and GitHub 378
Requesting Data Using an API Call 378
Installing Requests 379
Processing an API Response 379
Working with the Response Dictionary 380
Summarizing the Top Repositories 382
Monitoring API Rate Limits . 383
Visualizing Repositories Using Pygal 384
Refining Pygal Charts . 386
Adding Custom Tooltips 387
Plotting the Data 388
Adding Clickable Links to Our Graph . 390
The Hacker News API 390
Exercise 17-1: Other Languages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393
Exercise 17-2: Active Discussions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393
Exercise 17-3: Testing python_repos.py . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393
Summary . 393
Project 3: Web Applications
18 Getting Started with Django 397
Setting Up a Project . 398
Writing a Spec 398
Creating a Virtual Environment 398
Installing virtualenv . 399
Activating the Virtual Environment 399
Installing Django 400
Creating a Project in Django . 400
Creating the Database 401
Viewing the Project 401
Exercise 18-1: New Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402
Starting an App 403
Defining Models 403
Activating Models 404
The Django Admin Site . 406
Defining the Entry Model . 408
Migrating the Entry Model . 409
Registering Entry with the Admin Site 409
The Django Shell 410
Exercise 18-2: Short Entries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
Exercise 18-3: The Django API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
Exercise 18-4: Pizzeria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
Making Pages: The Learning Log Home Page . 412
Mapping a URL . 413
Writing a View 414
Writing a Template 415
Exercise 18-5: Meal Planner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416
Exercise 18-6: Pizzeria Home Page . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416
Building Additional Pages 416
Template Inheritance 416
The Topics Page . 418
Individual Topic Pages 421
Exercise 18-7: Template Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . 424
Exercise 18-8: Pizzeria Pages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424
Summary . 425
19
User Accounts 427
Allowing Users to Enter Data 428
Adding New Topics . 428
Adding New Entries . 432
Editing Entries 435
Exercise 19-1: Blog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438
Setting Up User Accounts . 439
The users App 439
The Login Page 440
Logging Out 442
The Registration Page . 443
Exercise 19-2: Blog Accounts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
Allowing Users to Own Their Data 446
Restricting Access with @login_required 447
Connecting Data to Certain Users 448
Restricting Topics Access to Appropriate Users 451
Protecting a User’s Topics . 451
Protecting the edit_entry Page 452
Associating New Topics with the Current User . 453
Exercise 19-3: Refactoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454
Exercise 19-4: Protecting new_entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454
Exercise 19-5: Protected Blog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454
Summary . 454
20 Styling and Deploying an App 455
Styling Learning Log 456
The django-bootstrap3 App . 456
Using Bootstrap to Style Learning Log . 457
Modifying base.html . 458
Styling the Home Page Using a Jumbotron 461
Styling the Login Page 461
Styling the new_topic Page 463
Styling the Topics Page . 463
Styling the Entries on the Topic Page 464
Exercise 20-1: Other Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466
Exercise 20-2: Stylish Blog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466
Deploying Learning Log . 466
Making a Heroku Account 466
Installing the Heroku Toolbelt . 466
Installing Required Packages . 466
Creating a Packages List with a requirements.txt File 467
Specifying the Python Runtime . 468
Modifying settings.py for Heroku . 468
Making a Procfile to Start Processes . 469
Modifying wsgi.py for Heroku . 470
Making a Directory for Static Files 470
Using the gunicorn Server Locally . 470
Using Git to Track the Project’s Files . 471
Pushing to Heroku 473
Setting Up the Database on Heroku 474
Refining the Heroku Deployment 475
Securing the Live Project . 476
Committing and Pushing Changes 477
Creating Custom Error Pages . 478
Ongoing Development 480
The SECRET_KEY Setting . 481
Deleting a Project on Heroku . 481
Exercise 20-3: Live Blog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
Exercise 20-4: More 404s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
Exercise 20-5: Extended Learning Log . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
Summary . 482
Afterword 483
A Installing Python 485
Python on Linux . 485
Finding the Installed Version 486
Installing Python 3 on Linux . 486
Python on OS X 486
Finding the Installed Version 486
Using Homebrew to Install Python 3 . 487
Python on Windows 488
Installing Python 3 on Windows . 488
Finding the Python Interpreter 488
Adding Python to Your Path Variable 489
Python Keywords and Built-in Functions 489
Python Keywords . 489
Python Built-in Functions 490
B Text Editors 491
Geany . 492
Installing Geany on Linux 492
Installing Geany on Windows 492
Running Python Programs in Geany 493
Customizing Geany Settings 493
Sublime Text . 494
Installing Sublime Text on OS X . 494
Installing Sublime Text on Linux 494
Installing Sublime Text on Windows . 495
Running Python Programs in Sublime Text 495
Configuring Sublime Text 495
Customizing Sublime Text Settings 496
IDLE . . 496
Installing IDLE on Linux 496
Installing IDLE on OS X . 496
Installing IDLE on Windows . 497
Customizing IDLE Settings . 497
Emacs and vim . 497
C Getting Help 499
First Steps. . . 499
Try It Again . 500
Take a Break . 500
Refer to This Book’s Resources . 500
Searching Online 501
Stack Overflow 501
The Official Python Documentation . 501
Official Library Documentation . 502
r/learnpython 502
Blog Posts . 502
IRC (Internet Relay Chat) 502
Make an IRC Account . 502
Channels to Join 503
IRC Culture 503
D Using Git for Version Control 505
Installing Git . 506
Installing Git on Linux . 506
Installing Git on OS X . 506
Installing Git on Windows . 506
Configuring Git 506
Making a Project . . . 507
Ignoring Files 507
Initializing a Repository 507
Checking the Status . 508
Adding Files to the Repository . 508
Making a Commit . 509
Checking the Log 509
The Second Commit 510
Reverting a Change . . . 511
Checking Out Previous Commits . 512
Deleting the Repository 513
Index 515


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Who Is This Book For?
The goal of this book is to bring you up to speed with Python as quickly as
possible so you can build programs that work—games, data visualizations,
and web applications—while developing a foundation in programming that
will serve you well for the rest of your life. Python Crash Course is written for
people of any age who have never programmed in Python before or have
never programmed at all. If you want to learn the basics of programming
quickly so you can focus on interesting projects, and you like to test your
understanding of new concepts by solving meaningful problems, this book
is for you. Python Crash Course is also perfect for middle school and high
school teachers who want to offer their students a project-based introduction
to programming.

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