Think Python - Denison University

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$Math 232 syllabus - Denison University$

$Math 102 syllabus - Personal Pages - Denison University$

42 Chapter 5. Conditionals and recursion5.7 NestedconditionalsOne conditional can also be nested within another. We could have written the trichotomy examplelikethis:if x == y:print 'x and y are equal'else:if x < y:print 'x is less than y'else:print 'x is greater than y'Theouterconditionalcontainstwobranches. Thefirstbranchcontainsasimplestatement. Thesecondbranch contains another if statement, which has two branches of its own. Those two branchesareboth simplestatements, although they could have been conditional statements as well.Although the indentation of the statements makes the structure apparent, nested conditionals becomedifficult toread very quickly. Ingeneral, itisagood idea toavoid them when you can.Logical operators often provide a way to simplify nested conditional statements. For example, wecan rewritethe following code using asingleconditional:if 0 < x:if x < 10:print 'x is a positive single-digit number.'The print statement is executed only if we make it past both conditionals, so we can get the sameeffect withtheandoperator:if 0 < x and x < 10:print 'x is a positive single-digit number.'5.8 RecursionIt is legal for one function to call another; it is also legal for a function to call itself. It may not beobviouswhythatisagoodthing,butitturnsouttobeoneofthemostmagicalthingsaprogramcando. For example, look at thefollowing function:def countdown(n):if n >> countdown(3)
5.9. Stack diagrams for recursive functions 43The execution of countdown begins with n=3, and since n is greater than 0, it outputs the value 3,and then calls itself...The execution of countdown begins with n=2, and since n is greater than 0, it outputsthe value 2, and then callsitself...The execution of countdown begins with n=1, and since n is greater than 0,itoutputs thevalue 1, and then calls itself...The execution of countdown begins with n=0, and since n is notgreater than 0, itoutputs the word, “Blastoff!” and thenreturns.Thecountdownthat gotn=1returns.Thecountdownthat gotn=2returns.Thecountdownthat gotn=3returns.And then you’reback in__main__. So, thetotal output looks likethis:321Blastoff!A function that calls itselfisrecursive; theprocess iscalled recursion.As another example, we can writeafunction that printsastringntimes.def print_n(s, n):if n
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Think PythonHowto Think LikeaComput
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Copyright©2008 AllenDowney.Printin
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viChapter 0. PrefaceIn 2003 I start
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viiiChapter 0. Preface• Keith Ver
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xChapter 0. Preface• Patryk Wolow
Page 12 and 13: xiiContents3 Functions 173.1 Functi
Page 14 and 15: xivContents7 Iteration 637.1 Multip
Page 16 and 17: xviContents12 Tuples 11512.1 Tuples
Page 18 and 19: xviiiContents17 Classes and methods
Page 20 and 21: xxContents
Page 22: 2 Chapter 1. The way of theprogramp
Page 25 and 26: 1.4. Formal and natural languages 5
Page 27 and 28: 1.7. Glossary 7Your job is to be a
Page 29 and 30: Chapter 2Variables,expressions ands
Page 31 and 32: 2.3. Variable names and keywords 11
Page 33 and 34: 2.6. Expressions 132.6 ExpressionsA
Page 35 and 36: 2.10. Debugging 152.10 DebuggingAtt
Page 37 and 38: Chapter 3Functions3.1 Functioncalls
Page 39 and 40: 3.4. Composition 19>>> math.sqrt(2)
Page 41 and 42: 3.7. Flow of execution 21def repeat
Page 43 and 44: 3.10. Stack diagrams 23Thisfunction
Page 45 and 46: 3.12. Why functions? 253.12 Whyfunc
Page 47 and 48: 3.15. Exercises 27Here’s an examp
Page 49 and 50: Chapter 4Case study: interfacedesig
Page 51 and 52: 4.3. Exercises 31The syntax of a fo
Page 53 and 54: 4.6. Interface design 33This draws
Page 55 and 56: 4.8. A development plan 354.8 Adeve
Page 57 and 58: 4.12. Exercises 37Exercise 4.2 Writ
Page 59 and 60: Chapter 5Conditionals and recursion
Page 61: 5.5. Alternative execution 41if sta
Page 65 and 66: 5.11. Keyboard input 455.11 Keyboar
Page 67 and 68: 5.14. Exercises 47relational operat
Page 69 and 70: 5.14. Exercises 492. Write a functi
Page 71 and 72: Chapter 6Fruitfulfunctions6.1 Retur
Page 73 and 74: 6.2. Incremental development 53>>>
Page 75 and 76: 6.5. More recursion 55It is common
Page 77 and 78: 6.6. Leap of faith 57__main__factor
Page 79 and 80: 6.9. Debugging 59The first base cas
Page 81 and 82: 6.11. Exercises 61sum = x + y + zpo
Page 83 and 84: Chapter 7Iteration7.1 Multipleassig
Page 85 and 86: 7.4. break 652. Iftheconditionisfal
Page 87 and 88: 7.6. Algorithms 672.00001024003>>>
Page 89 and 90: 7.9. Exercises 69decrement: An upda
Page 91 and 92: Chapter 8Strings8.1 Astringis a seq
Page 93 and 94: 8.4. String slices 73Thefollowingex
Page 95 and 96: 8.7. Looping and counting 75This is
Page 97 and 98: 8.10. String comparison 778.10 Stri
Page 99 and 100: 8.12. Glossary 798.12 Glossaryobjec
Page 101 and 102: Chapter 9Case study: word play9.1 R
Page 103 and 104: 9.3. Search 83Exercise 9.6 Write a
Page 105 and 106: 9.5. Debugging 85Here is a version
Page 107 and 108: 9.7. Exercises 87Write a Python pro
Page 109 and 110: Chapter 10Lists10.1 Alist isasequen
Page 111 and 112: 10.3. Traversing alist 9110.3 Trave
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10.7. Map, filter and reduce 93List
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10.9. Listsand strings 95>>> t = ['
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10.12. Listarguments 97The statedia
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10.14. Glossary 99word = word.strip
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10.15. Exercises 101Exercise 10.6 W
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Chapter 11DictionariesAdictionaryis
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11.1. Dictionary as asetof counters
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11.4. Dictionaries and lists 107Thi
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11.5. Memos 109corresponding locati
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11.7. Long integers 111count = 0def
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11.10. Exercises 113implementation:
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Chapter 12Tuples12.1 Tuples areimmu
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12.3. Tuples as return values 117>>
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12.6. Dictionaries and tuples 119If
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12.7. Comparing tuples 12112.7 Comp
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12.10. Glossary 123>>> t3 = [1, 2,
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Chapter 13Case study: data structur
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13.3. Word histogram 12713.3 Word h
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13.6. Dictionary subtraction 129num
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13.9. Datastructures 131In this tex
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13.11. Glossary 133reading: Examine
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Chapter 14Files14.1 PersistenceMost
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14.4. Filenames and paths 137>>> '%
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14.6. Databases 139Python starts by
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14.9. Writingmodules 141The argumen
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14.11. Glossary 14314.11 Glossarype
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Chapter 15Classes and objects15.1 U
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15.3. Rectangles 147>>> print '(%g,
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15.6. Copying 149>>> print box.widt
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15.8. Glossary 151>>> hasattr(p, 'x
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Chapter 16Classes and functions16.1
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16.3. Modifiers 155if sum.second >=
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16.5. Debugging 157But if we have t
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Chapter 17Classes and methods17.1 O
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17.3. Another example 161Inside the
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17.6. The str method 163>>> time =
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17.9. Polymorphism 165Unfortunately
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17.12. Exercises 167object-oriented
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Chapter 18InheritanceIn this chapte
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18.3. Comparing cards 171Thefirstel
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18.6. Add, remove, shuffle and sort
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18.8. Classdiagrams 175So when you
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18.10. Glossary 177might get the on
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18.11. Exercises 1796. Print a tabl
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Chapter 19Case study: Tkinter19.1 G
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19.3. Canvas widgets 183Exercise 19
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19.6. Packing widgets 185>>> text.i
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19.6. Packing widgets 187self.bu(te
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19.8. Binding 18919.8 BindingAbindi
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19.9. Debugging 19119.9 DebuggingOn
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19.11. Exercises 193image = PIL.ope
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Appendix ADebuggingDifferentkindsof
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A.2. Runtime errors 197A.2 Runtime
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A.3. Semantic errors 199• You are
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A.3. Semantic errors 201The explici
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Indexabecedarian, 72, 83abs functio
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Index 205experimental, 4superstitio
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Index 207raw input, 45recursive, 43
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Index 209map pattern, 93, 100map to
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Index 211poker, 169, 178polygon fun
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Index 213knowing the answer, 53leap
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Think Python - Denison University

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