Preface iii
Special Features xviii
1 Introduction 1
1.1 Computer Programs 2
1.2 The Anatomy of a Computer 3
CS1 Computers Are Everywhere 5
1.3 The Python Programming Language 5
1.4 Becoming Familiar with Your Programming Environment 6
PT1 Interactive Mode 8
PT2 Backup Copies 9
ST1 The Python Interpreter 10
1.5 Analyzing Your First Program 11
1.6 Errors 13
CE1 Misspelling Words 14
1.7 PROBLEM SOLVING: Algorithm Design 15
CS2 Data Is Everywhere 17
HT1 Describing an Algorithm with Pseudocode 18
WE1 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
CE1 Using Undefined Variables 30
Pt1 Choose Descriptive Variable Names 30
PT2 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
CE2 Roundoff Errors 36
CE3 Unbalanced Parentheses 37
PT3 Use Spaces in Expressions 37
ST1 Other Ways to Import Modules 38
ST2 Combining Assignment and Arithmetic 38
ST3 Line Joining 38
2.3 PROBLEM SOLVING: First Do It By Hand 39
WE1 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
ST4 Character Values 46
ST5 Escape Sequences 47
CS1 International Alphabets and Unicode 47
2.5 Input and Output 48
User Input 48
Numerical Input 49
Formatted Output 50
PT4 Don't Wait to Convert 53
HT1 Writing Simple Programs 53
WE2 Computing the Cost of Stamps 56
CS2 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
HT2 GRAPHICS: Drawing Graphical Shapes 65
TOOLBOX 1 Symbolic Processing with SymPy 68
3 Decisions 73
3.1 The if Statement 74
CE1 Tabs 77
PT1 Avoid Duplication in Branches 78
ST1 Conditional Expressions 78
3.2 Relational Operators 79
CE2 Exact Comparison of Floating-Point Numbers 82
ST2 Lexicographic Ordering of Strings 82
HT1 Implementing an if Statement 83
WE1 Extracting the Middle 85
3.3 Nested Branches 87
PT2 Hand-Tracing 89
CS1 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
PT3 Make a Schedule and Make Time for Unexpected Problems 100
3.7 Boolean Variables and Operators 101
CE3 Confusing and and or Conditions 104
PT4 Readability 104
ST3 Chaining Relational Operators 105
ST4 Short-Circuit Evaluation of Boolean Operators 105
ST5 De Morgan's Law 106
3.8 Analyzing Strings 106
3.9 APPLICATION: Input Validation 110
ST6 Terminating a Program 112
ST7 Interactive Graphical Programs 112
CS2 Artificial Intelligence 113
WE2 GRAPHICS: Intersecting Circles 113
TOOLBOX 2 Plotting Simple Graphs 117
4 Loops 125
4.1 The while Loop 126
CE1 Don't Think "Are We There Yet?" 130
CE2 Infinite Loops 130
CE3 Off-by-One Errors 131
ST1 Special Form of the print Function 132
CS1 The First Bug 132
4.2 PROBLEM SOLVING: Hand-Tracing 133
4.3 APPLICATION: Processing Sentinel Values 135
ST2 Processing Sentinel Values with a Boolean Variable 138
ST3 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
PT1 Count Iterations 148
HT1 Writing a Loop 149
4.7 Nested Loops 152
WE1 Average Exam Grades 155
WE2 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
WE3 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
CS2 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
PT1 Function Comments 189
PT2 Naming Functions 190
5.3 Parameter Passing 190
PT3 Do Not Modify Parameter Variables 191
CE1 Trying to Modify Arguments 192
5.4 Return Values 192
ST1 Using Single-Line Compound Statements 193
HT1 Implementing a Function 194
WE1 Generating Random Passwords 196
5.5 Functions Without Return Values 201
CS1 Personal Computing 202
5.6 PROBLEM SOLVING: Reusable Functions 203
5.7 PROBLEM SOLVING: Stepwise Refinement 205
PT4 Keep Functions Short 209
PT5 Tracing Functions 210
PT6 Stubs 211
WE2 Calculating a Course Grade 211
WE3 Using a Debugger 214
5.8 Variable Scope 219
PT7 Avoid Global Variables 221
WE4 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
WE5 Plotting Growth or Decay 230
5.10 Recursive Functions (Optional) 232
HT2 Thinking Recursively 234
TOOLBOX 1 Turtle Graphics 236
6 Lists 245
6.1 Basic Properties of Lists 246
Creating Lists 246
Accessing List Elements 247
Traversing Lists 248
List References 249
CE1 Out-of-Range Errors 250
PT1 Use Lists for Sequences of Related Items 250
ST1 Negative Subscripts 250
ST2 Common Container Functions 251
CS1 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
ST3 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
WE1 Plotting Trigonometric Functions 265
6.4 Using Lists with Functions 268
ST4 Call by Value and Call by Reference 271
ST5 Tuples 271
ST6 Functions with a Variable Number of Arguments 272
ST7 Tuple Assignment 272
ST8 Returning Multiple Values with Tuples 273
TOOLBOX 1 Editing Sound Files 273
6.5 PROBLEM SOLVING: Adapting Algorithms 275
HT1 Working with Lists 276
WE2 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
WE3 A World Population Table 290
ST9 Tables with Variable Row Lengths 292
WE4 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
CE1 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
ST1 Reading the Entire File 312
ST2 Regular Expressions 312
ST3 Character Encodings 313
TOOLBOX 1 Working with CSV Files 314
7.3 Command Line Arguments 316
HT1 Processing Text Files 319
WE1 Analyzing Baby Names 322
TOOLBOX 2 Working with Files and Directories 325
CS1 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
WE2 GRAPHICS: Displaying a Scene File 334
7.5 Exception Handling 337
Raising Exceptions 338
Handling Exceptions 339
The finally Clause 341
PT1 Raise Early, Handle Late 342
PT2 Do Not Use except and finally in the Same try Statement 342
ST4 The with Statement 343
TOOLBOX 3 Reading Web Pages 343
7.6 APPLICATION: Handling Input Errors 344
TOOLBOX 4 Statistical Analysis 348
WE3 Creating a Bubble Chart 352
CS2 The Ariane Rocket Incident 355
8 Sets and Dictionaries 357
8.1 Sets 358
Creating and Using Sets 358
Adding and Removing Elements 359
Subsets 360
Set Union, Intersection, and Difference 361
WE1 Counting Unique Words 364
PT1 Use Python Sets, Not Lists, for Efficient Set Operations 366
ST1 Hashing 367
CS1 Standardization 368
8.2 Dictionaries 368
Creating Dictionaries 369
Accessing Dictionary Values 370
Adding and Modifying Items 370
Removing Items 371
Traversing a Dictionary 372
ST2 Iterating over Dictionary Items 374
ST3 Storing Data Records 375
WE2 Translating Text Messages 375
8.3 Complex Structures 378
A Dictionary of Sets 378
A Dictionary of Lists 381
ST4 User Modules 383
WE3 GRAPHICS: Pie Charts 384
TOOLBOX 1 Harvesting JSON Data from the Web 388
9 Objects and Classes 393
9.1 Object-Oriented Programming 394
9.2 Implementing a Simple Class 396
9.3 Specifying the Public Interface of a Class 399
9.4 Designing the Data Representation 401
PT1 Make All Instance Variables Private, Most Methods Public 402
9.5 Constructors 402
CE1 Trying to Call a Constructor 404
ST1 Default and Named Arguments 404
9.6 Implementing Methods 405
PT2 Define Instance Variables Only in the Constructor 407
ST2 Class Variables 408
9.7 Testing a Class 409
HT1 Implementing a Class 410
WE1 Implementing a Bank Account Class 414
9.8 PROBLEM SOLVING: Tracing Objects 416
9.9 PROBLEM SOLVING: Patterns for Object Data 419
Keeping a Total 419
Counting Events 420
Collecting Values 420
Managing Properties of an Object 421
Modeling Objects with Distinct States 421
Describing the Position of an Object 422
9.10 Object References 423
Shared References 424
The None Reference 425
The self Reference 426
The Lifetime of Objects 426
CS1 Electronic Voting 427
9.11 APPLICATION: Writing a Fraction Class 428
Fraction Class Design 428
The Constructor 429
Special Methods 430
Arithmetic Operations 432
Logical Operations 433
ST3 Object Types and Instances 435
WE2 GRAPHICS: A Die Class 436
CS2 Open Source and Free Software 439
10 Inheritance 443
10.1 Inheritance Hierarchies 444
PT1 Use a Single Class for Variation in Values, Inheritance for Variation in Behavior 447
ST1 The Cosmic Superclass: object 447
10.2 Implementing Subclasses 449
CE1 Confusing Super- and Subclasses 451
10.3 Calling the Superclass Constructor 452
10.4 Overriding Methods 455
CE2 Forgetting to Use the super Function When Invoking a Superclass Method 458
10.5 Polymorphism 458
ST2 Subclasses and Instances 461
ST3 Dynamic Method Lookup 461
ST4 Abstract Classes 462
CE3 Don't Use Type Tests 463
HT1 Developing an Inheritance Hierarchy 463
WE1 Implementing an Employee Hierarchy for Payroll Processing 468
10.6 APPLICATION: A Geometric Shape Class Hierarchy 472
The Base Class 472
Basic Shapes 474
Groups of Shapes 477
TOOLBOX 1 Game Programming 480
11 Recursion 489
11.1 Triangle Numbers Revisited 490
CE1 Infinite Recursion 493
ST1 Recursion with Objects 493
11.2 PROBLEM SOLVING: Thinking Recursively 494
WE1 Finding Files 497
11.3 Recursive Helper Functions 498
11.4 The Efficiency of Recursion 499
11.5 Permutations 504
CS1 The Limits of Computation 506
11.6 Backtracking 508
WE2 Towers of Hanoi 512
11.7 Mutual Recursion 515
TOOLBOX 1 Analyzing Web Pages with Beautiful Soup 519
12 Sorting and Searching 525
12.1 Selection Sort 526
12.2 Profiling the Selection Sort Algorithm 528
12.3 Analyzing the Performance of the Selection Sort Algorithm 530
ST1 Oh, Omega, and Theta 531
ST2 Insertion Sort 532
12.4 Merge Sort 534
12.5 Analyzing the Merge Sort Algorithm 536
ST3 The Quicksort Algorithm 538
CS1 The First Programmer 540
12.6 Searching 541
Linear Search 541
Binary Search 542
12.7 PROBLEM SOLVING: Estimating the Running Time of an Algorithm 544
Linear Time 545
Quadratic Time 546
The Triangle Pattern 547
Logarithmic Time 548
PT1 Searching and Sorting 549
ST4 Comparing Objects 549
WE1 Enhancing the Insertion Sort Algorithm 549
Appendix A Python Operator Summary A-1
Appendix B Python Reserved Word Summary A-3
Appendix C The Python Standard Library A-5
Appendix D The Basic Latin and Latin-1 Subsets of Unicode A-22
Appendix E Binary Numbers and Bit Operations*
Appendix F HTML Summary*
Glossary R-1
Index R-6
Credits R-22
Quick Reference R-23
