1 Introduction 1

2 A Case for Puzzle-based Learning 5

2.1 Overcome the Knowledge Gap . . . . . . . 6

2.2 Embrace the Eureka Moment . . . . . . . 7

2.3 Divide and Conquer . . . . . . . . . . . . 8

2.4 Improve From Immediate Feedback . . . . 9

2.5 Measure Your Skills . . . . . . . . . . . . . 10

2.6 Individualized Learning . . . . . . . . . . . 12

2.7 Small is Beautiful . . . . . . . . . . . . . . 12

2.8 Active Beats Passive Learning . . . . . . . 14

2.9 Make Code a First-class Citizen . . . . . . 16

2.10 What You See is All There is . . . . . . . 18

3 The Elo Rating for Python 21

3.1 How to Use This Book . . . . . . . . . . . 21

3.2 How to Test and Train Your Skills? . . . . 23

3.3 What Can This Book Do For You? . . . . 27

4 A Quick Overview of the Python Language 31

4.1 Keywords . . . . . . . . . . . . . . . . . . 32

4.2 Basic Data Types . . . . . . . . . . . . . . 35

4.3 Complex Data Types . . . . . . . . . . . . 38

4.4 Classes . . . . . . . . . . . . . . . . . . . . 43

4.5 Functions and Tricks . . . . . . . . . . . . 46

5 Puzzles: Basic to Scholar 51

5.1 Printing values . . . . . . . . . . . . . . . 51

5.2 Basics of variables . . . . . . . . . . . . . . 53

5.3 Getting started with strings . . . . . . . . 54

5.4 Types of variables I . . . . . . . . . . . . . 55

5.5 Types of Variables II . . . . . . . . . . . . 56

5.6 Minimum . . . . . . . . . . . . . . . . . . 57

5.7 String Concatenation . . . . . . . . . . . . 58

5.8 Line Breaks I . . . . . . . . . . . . . . . . 59

5.9 Line Breaks II . . . . . . . . . . . . . . . . 60

5.10 List Length . . . . . . . . . . . . . . . . . 61

5.11 Comparison Operators I . . . . . . . . . . 62

5.12 Comparison Operators II . . . . . . . . . . 63

5.13 Multiple Initializations . . . . . . . . . . . 64

6 Puzzles: Scholar to Intermediate 67

6.1 Maximum . . . . . . . . . . . . . . . . . . 67

6.2 Memory addresses . . . . . . . . . . . . . . 68

6.3 Swapping Values . . . . . . . . . . . . . . 69

6.4 The Boolean Operator AND . . . . . . . . 70

6.5 The Boolean Operator OR . . . . . . . . . 72

6.6 Boolean Operators . . . . . . . . . . . . . 74

6.7 Arithmetic Expressions . . . . . . . . . . . 76

6.8 Integer Division and Modulo . . . . . . . . 78

6.9 Building Strings . . . . . . . . . . . . . . . 80

6.10 The len() Function . . . . . . . . . . . . 81

6.11 String Indices . . . . . . . . . . . . . . . . 82

6.12 The upper() Function . . . . . . . . . . . . 83

6.13 The lower() Function . . . . . . . . . . . . 84

6.14 Somebody Is Shouting . . . . . . . . . . . 85

6.15 Counting Characters . . . . . . . . . . . . 86

6.16 String Lengths . . . . . . . . . . . . . . . 87

6.17 Finding Characters in Strings . . . . . . . 88

6.18 Not Finding Characters in Strings . . . . . 89

6.19 Counting Letters . . . . . . . . . . . . . . 90

6.20 Min() and Max() of a String . . . . . . . . 91

6.21 Reversed Strings . . . . . . . . . . . . . . 92

6.22 String Equality . . . . . . . . . . . . . . . 93

6.23 Slicing I . . . . . . . . . . . . . . . . . . . 95

6.24 Slicing II . . . . . . . . . . . . . . . . . . . 96

6.25 Slicing III . . . . . . . . . . . . . . . . . . 97

6.26 Slicing IV . . . . . . . . . . . . . . . . . . 98

6.27 Slicing V . . . . . . . . . . . . . . . . . . . 99

6.28 Memory Addresses and Slicing . . . . . . . 100

6.29 Accessing List Items I . . . . . . . . . . . 101

6.30 Accessing List Items II . . . . . . . . . . . 103

6.31 List as Stack . . . . . . . . . . . . . . . . . 104

6.32 More String Operations . . . . . . . . . . 105

6.33 Checking for Substrings . . . . . . . . . . 106

6.34 Stripping String Boundaries . . . . . . . . 107

6.35 Strings: Stripping vs. Replacement . . . . 108

6.36 Glueing Strings Together . . . . . . . . . . 109

6.37 The Copy Operation . . . . . . . . . . . . 110

6.38 Growing List Contents I . . . . . . . . . . 111

6.39 Growing List Contents II . . . . . . . . . . 112

6.40 List Operations I . . . . . . . . . . . . . . 114

6.41 List Operations II . . . . . . . . . . . . . . 115

6.42 List Operations III . . . . . . . . . . . . . 116

6.43 List Operations IV . . . . . . . . . . . . . 117

6.44 List Operations V . . . . . . . . . . . . . . 117

6.45 List Operations VI . . . . . . . . . . . . . 118

6.46 List Operations VII . . . . . . . . . . . . . 119

6.47 List Operations VIII . . . . . . . . . . . . 120

6.48 List Operations IX . . . . . . . . . . . . . 121

6.49 List Operations X . . . . . . . . . . . . . . 122

6.50 Lists and the Range Function I . . . . . . 123

6.51 Lists and the Range Function II . . . . . . 124

6.52 Lists and the Range Function III . . . . . 125

6.53 Python’s Multiple Assignment I . . . . . . 126

6.54 Slice Assignments . . . . . . . . . . . . . . 127

6.55 Strings and Lists II . . . . . . . . . . . . . 128

6.56 String Comparisons . . . . . . . . . . . . . 129

6.57 From Booleans to Strings . . . . . . . . . . 130

6.58 Boolean Trickery I . . . . . . . . . . . . . 131

6.59 Boolean Trickery II . . . . . . . . . . . . . 132

6.60 Boolean Trickery III . . . . . . . . . . . . 133

6.61 Looping over Ranges . . . . . . . . . . . . 134

6.62 Reversed Loops . . . . . . . . . . . . . . . 135

6.63 Boolean Trickery IV . . . . . . . . . . . . 136

6.64 Lists and Memory Addresses . . . . . . . . 137

6.65 List Objects . . . . . . . . . . . . . . . . . 138

6.66 Boolean Tricks . . . . . . . . . . . . . . . 139

6.67 Complex Numbers . . . . . . . . . . . . . 140

6.68 Tuples . . . . . . . . . . . . . . . . . . . . 141

6.69 Multiple Assignments . . . . . . . . . . . . 142

6.70 Boolean Integer Conversion . . . . . . . . 143

6.71 The any() Function . . . . . . . . . . . . 144

6.72 The sum() Function . . . . . . . . . . . . 146

6.73 Accessing Complex Numbers . . . . . . . . 148

6.74 Tuple Confusion . . . . . . . . . . . . . . . 149

6.75 Understanding While ... Else (1/3) . . . . 150

6.76 Understanding While ... Else (2/3) . . . . 151

6.77 Understanding While ... Else (3/3) . . . . 153

6.78 Basic Arithmetic . . . . . . . . . . . . . . 155

6.79 Dictionary . . . . . . . . . . . . . . . . . . 156

6.80 Dictionary of Dictionaries . . . . . . . . . 158

6.81 Reverse Dictionary Index . . . . . . . . . . 160

6.82 Default Arguments . . . . . . . . . . . . . 162

7 Puzzles: Intermediate to Professional 165

7.1 Building Strings II . . . . . . . . . . . . . 165

7.2 String: Slicing and Indexing . . . . . . . . 167

7.3 Built-in Python Operations . . . . . . . . 168

7.4 Strings and Lists I . . . . . . . . . . . . . 169

7.5 Formatting Printouts . . . . . . . . . . . . 170

7.6 Floating Point Comparisons . . . . . . . . 172

7.7 Python’s Multiple Assignment II . . . . . 174

7.8 The Not-So-Obvious Case . . . . . . . . . 175

7.9 Rounding Values . . . . . . . . . . . . . . 176

7.10 Initializing Integers . . . . . . . . . . . . . 177

7.11 Basic Typing . . . . . . . . . . . . . . . . 178

7.12 Short Circuiting . . . . . . . . . . . . . . . 179

7.13 While Arithmetic . . . . . . . . . . . . . . 182

7.14 The Lambda Function . . . . . . . . . . . 183

7.15 Zip . . . . . . . . . . . . . . . . . . . . . . 184

7.16 Basic Filtering . . . . . . . . . . . . . . . . 186

7.17 List Comprehension . . . . . . . . . . . . . 188

7.18 Encryption by Obfuscation . . . . . . . . . 190

7.19 String Dictionary . . . . . . . . . . . . . . 193

7.20 Lambda Function . . . . . . . . . . . . . . 194

7.21 Dictionary of Dictionaries . . . . . . . . . 196

7.22 Sorting Dictionary Keys . . . . . . . . . . 198

7.23 Pythonic Loop Iteration . . . . . . . . . . 200

7.24 Filtering with List Comprehension . . . . . 202

7.25 Aggregating with List Comprehension . . . 204

7.26 Maximum of Tuples . . . . . . . . . . . . . 206

7.27 The Key Argument . . . . . . . . . . . . . 208

7.28 Puzzle 123 . . . . . . . . . . . . . . . . . . 210

7.29 Set Operations (1/2) . . . . . . . . . . . . 211

7.30 Set Operations (2/2) . . . . . . . . . . . . 212

7.31 Recursive Algorithm . . . . . . . . . . . . 214

7.32 Fibonacci . . . . . . . . . . . . . . . . . . 218

8 Final Remarks 221

Your skill level . . . . . . . . . . . . . . . 221

Where to go from here? . . . . . . . . . . 222

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