Preface iii Special Features xviii 1 Introduction 1 1.1 Computer Programs 2 1.2 The Anatomy of a Computer 3 CS 1 Computers Are Everywhere 5 1.3 The Python Programming Language 5 1.4 Becoming Familiar with Your Programming Environment 6 PT 1 Interactive Mode 8 PT 2 Backup Copies 9 ST 1 The Python Interpreter 10 1.5 Analyzing Your First Program 11 1.6 Errors 13 CE 1 Misspelling Words 14 1.7 PROBLEM SOLVING: Algorithm Design 15 CS 2 Data Is Everywhere 17 HT 1 Describing an Algorithm with Pseudocode 18 WE 1 Writing an Algorithm for Tiling a Floor 20 2 Programming With Numbers and Strings 23 2.

1 Variables 24 Defining Variables 24 Number Types 26 Variable Names 27 Constants 28 Comments 29 CE 1 Using Undefined Variables 30 PT 1 Choose Descriptive Variable Names 30 PT 2 Do Not Use Magic Numbers 30 2.2 Arithmetic 31 Basic Arithmetic Operations 31 Powers 32 Floor Division and Remainder 32 Calling Functions 33 Mathematical Functions 35 CE 2 Roundoff Errors 36 CE 3 Unbalanced Parentheses 37 PT 3 Use Spaces in Expressions 37 ST 1 Other Ways to Import Modules 38 ST 2 Combining Assignment and Arithmetic 38 ST 3 Line Joining 38 2.3 PROBLEM SOLVING: First Do It By Hand 39 WE 1 Computing Travel Time 40 2.4 Strings 41 The String Type 41 Concatenation and Repetition 42 Converting Between Numbers and Strings 43 Strings and Characters 44 String Methods 45 ST 4 Character Values 46 ST 5 Escape Sequences 47 CS 1 International Alphabets and Unicode 47 2.5 Input and Output 48 User Input 48 Numerical Input 49 Formatted Output 50 PT 4 Don''t Wait to Convert 53 HT 1 Writing Simple Programs 53 WE 2 Computing the Cost of Stamps 56 CS 2 Bugs in Silicon 58 2.6 GRAPHICS: Simple Drawings 58 Creating a Window 59 Lines and Polygons 60 Filled Shapes and Color 62 Ovals, Circles, and Text 64 HT 2 GRAPHICS: Drawing Graphical Shapes 65 TOOLBOX 1 Symbolic Processing with SymPy 68 3 Decisions 73 3.1 The if Statement 74 CE 1 Tabs 77 PT 1 Avoid Duplication in Branches 78 ST 1 Conditional Expressions 78 3.2 Relational Operators 79 CE 2 Exact Comparison of Floating-Point Numbers 82 ST 2 Lexicographic Ordering of Strings 82 HT 1 Implementing an if Statement 83 WE 1 Extracting the Middle 85 3.

3 Nested Branches 87 PT 2 Hand-Tracing 89 CS 1 Dysfunctional Computerized Systems 90 3.4 Multiple Alternatives 91 TOOLBOX 1 Sending E-mail 93 3.5 PROBLEM SOLVING: Flowcharts 96 3.6 PROBLEM SOLVING: Test Cases 99 PT 3 Make a Schedule and Make Time for Unexpected Problems 100 3.7 Boolean Variables and Operators 101 CE 3 Confusing and and or Conditions 104 PT 4 Readability 104 ST 3 Chaining Relational Operators 105 ST 4 Short-Circuit Evaluation of Boolean Operators 105 ST 5 De Morgan''s Law 106 3.8 Analyzing Strings 106 3.9 APPLICATION: Input Validation 110 ST 6 Terminating a Program 112 ST 7 Interactive Graphical Programs 112 CS 2 Artificial Intelligence 113 WE 2 GRAPHICS: Intersecting Circles 113 TOOLBOX 2 Plotting Simple Graphs 117 4 Loops 125 4.1 The while Loop 126 CE 1 Don''t Think "Are We There Yet?" 130 CE 2 Infinite Loops 130 CE 3 Off-by-One Errors 131 ST 1 Special Form of the print Function 132 CS 1 The First Bug 132 4.

2 PROBLEM SOLVING: Hand-Tracing 133 4.3 APPLICATION: Processing Sentinel Values 135 ST 2 Processing Sentinel Values with a Boolean Variable 138 ST 3 Redirection of Input and Output 138 4.4 PROBLEM SOLVING: Storyboards 139 4.5 Common Loop Algorithms 141 Sum and Average Value 141 Counting Matches 142 Prompting Until a Match is Found 142 Maximum and Minimum 142 Comparing Adjacent Values 143 4.6 The for Loop 145 PT 1 Count Iterations 148 HT 1 Writing a Loop 149 4.7 Nested Loops 152 WE 1 Average Exam Grades 155 WE 2 A Grade Distribution Histogram 157 4.8 Processing Strings 159 Counting Matches 159 Finding All Matches 160 Finding the First or Last Match 160 Validating a String 161 Building a New String 162 4.9 APPLICATION: Random Numbers and Simulations 164 Generating Random Numbers 164 Simulating Die Tosses 165 The Monte Carlo Method 165 WE 3 GRAPHICS: Bull''s Eye 167 4.

10 GRAPHICS: Digital Image Processing 169 Filtering Images 170 Reconfiguring Images 172 4.11 PROBLEM SOLVING: Solve a Simpler Problem First 174 CS 2 Digital Piracy 180 5 Functions 183 5.1 Functions as Black Boxes 184 5.2 Implementing and Testing Functions 185 Implementing a Function 186 Testing a Function 186 Programs that Contain Functions 187 PT 1 Function Comments 189 PT 2 Naming Functions 190 5.3 Parameter Passing 190 PT 3 Do Not Modify Parameter Variables 191 CE 1 Trying to Modify Arguments 192 5.4 Return Values 192 ST 1 Using Single-Line Compound Statements 193 HT 1 Implementing a Function 194 WE 1 Generating Random Passwords 196 5.5 Functions Without Return Values 201 CS 1 Personal Computing 202 5.6 PROBLEM SOLVING: Reusable Functions 203 5.

7 PROBLEM SOLVING: Stepwise Refinement 205 PT 4 Keep Functions Short 209 PT 5 Tracing Functions 210 PT 6 Stubs 211 WE 2 Calculating a Course Grade 211 WE 3 Using a Debugger 214 5.8 Variable Scope 219 PT 7 Avoid Global Variables 221 WE 4 GRAPHICS: Rolling Dice 221 5.9 GRAPHICS: Building an Image Processing Toolkit 224 Getting Started 224 Comparing Images 225 Adjusting Image Brightness 226 Rotating an Image 227 Using the Toolkit 228 WE 5 Plotting Growth or Decay 230 5.10 Recursive Functions (Optional) 232 HT 2 Thinking Recursively 234 TOOLBOX 1 Turtle Graphics 236 LISTS 245 6.1 Basic Properties of Lists 246 Creating Lists 246 Accessing List Elements 247 Traversing Lists 248 List References 249 CE 1 Out-of-Range Errors 250 PT 1 Use Lists for Sequences of Related Items 250 ST 1 Negative Subscripts 250 ST 2 Common Container Functions 251 CS 1 Computer Viruses 251 6.2 List Operations 252 Appending Elements 252 Inserting an Element 253 Finding an Element 254 Removing an Element 254 Concatenation and Replication 255 Equality Testing 256 Sum, Maximum, Minimum, and Sorting 256 Copying Lists 256 ST 3 Slices 258 6.3 Common List Algorithms 259 Filling 259 Combining List Elements 259 Element Separators 260 Maximum and Minimum 260 Linear Search 261 Collecting and Counting Matches 261 Removing Matches 262 Swapping Elements 263 Reading Input 264 WE 1 Plotting Trigonometric Functions 265 6.4 Using Lists with Functions 268 ST 4 Call by Value and Call by Reference 271 ST 5 Tuples 271 ST 6 Functions with a Variable Number of Arguments 272 ST 7 Tuple Assignment 272 ST 8 Returning Multiple Values with Tuples 273 TOOLBOX 1 Editing Sound Files 273 6.

5 PROBLEM SOLVING: Adapting Algorithms 275 HT 1 Working with Lists 276 WE 2 Rolling the Dice 278 6.6 PROBLEM SOLVING: Discovering Algorithms by Manipulating Physical Objects 282 6.7 Tables 285 Creating Tables 286 Accessing Elements 287 Locating Neighboring Elements 287 Computing Row and Column Totals 288 Using Tables with Functions 289 WE 3 A World Population Table 290 ST 9 Tables with Variable Row Lengths 292 WE 4 GRAPHICS: Drawing Regular Polygons 293 7 Files and Exceptions 299 7.1 Reading and Writing Text Files 300 Opening a File 300 Reading from a File 301 Writing from a File 302 A File Processing Example 302 CE 1 Backslashes in File Names 303 7.2 Text Input and Output 304 Iterating over the Lines of a File 304 Reading Words 306 Reading Characters 308 Reading Records 309 ST 1 Reading the Entire File 312 ST 2 Regular Expressions 312 ST 3 Character Encodings 313 TOOLBOX 1 Working with CSV Files 314 7.3 Command Line Arguments 316 HT 1 Processing Text Files 319 WE 1 Analyzing Baby Names 322 TOOLBOX 2 Working with Files and Directories 325 CS 1 Encryption Algorithms 327 7.4 Binary Files and Random Access (Optional) 328 Reading and Writing Binary Files 328 Random Access 329 Image Files 330 Processing BMP Files 331 WE 2 GRAPHICS: Displaying a Scene File 334 7.5 Exception Handling 337 Raising Exceptions 338 Handling Exceptions 339 The finally Clause 341 PT 1 Raise Early, Handle Late 342 PT 2 Do Not Use except and finally in the Same try Statement 342 ST 4 The with Statement 343 TOOLBOX 3 Reading Web Pages 343 7.

6 APPLICATION: Handling Input Errors 344 TOOLBOX 4 Statistical Analysis 348 WE 3 Creating a Bubble Chart 352 CS 2 The Ariane Rocket Incident 355 8 Sets an.