Loops in Python - GitHub PagesRepetition with a while loop • while condition: # executes over and...

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Loops in Python CS 8: Introduction to Computer Science, Winter 2019 Lecture #7 Ziad Matni, Ph.D. Dept. of Computer Science, UCSB

Transcript of Loops in Python - GitHub PagesRepetition with a while loop • while condition: # executes over and...

Page 1: Loops in Python - GitHub PagesRepetition with a while loop • while condition: # executes over and over until a condition is False • While loops won’t run at all if condition

LoopsinPython

CS8:IntroductiontoComputerScience,Winter2019Lecture#7

ZiadMatni,Ph.D.

Dept.ofComputerScience,UCSB

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Administrative•  Myofficehours:rescheduledtoday:

2:30pm–3:30pm(justfortoday…)

•  Hw04–duenextweekonMONDAYinclass•  Lab03–duenextweekonMONDAYbymidnight

•  YoucancheckoldhomeworkonGradeScope

•  MidtermExam#1isnextWednesday!!!–  StudyGuidewillbeONOURWEBSITEbytomorrow

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Midterm#1Exam•  Feb.6th9:30AM–10:45AM•  InTHISclassroom(unlessyouareaDSPstudent)•  Come10MINUTESEARLYasthereispre-assignedseating•  CLOSEDBOOK!Butyoucanbring1pageofnotes

–  Single-sideonly,8.5”x11”–  Hand-writtenorcomputerprintedisOK!–  Mustturnitinwiththeexamwhendone–  Nocalculators/cellphones/anytypeofcomputer

•  BringyourUCSBIDwithyou.NOEXCEPTIONS.1/29/19 Matni,CS8,Wi19 3

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Midterm#1ExamWHAT’SONIT?!

•  Everything–  ReviewALLlectures–  ReviewALLreadings–  ReviewALLlabs–  ReviewALLhomework

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Midterm#1ExamSAMPLEQUESTIONS?!?!?!?!?!?!

•  Yes!SeeStudyGuideontheclasswebsite!

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LectureOutline•  Loops

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ClassExerciseGettogetherwith2or3otherpeoplearoundyouandanswerthisquestion.

Youcanuseyournotesfromlasttime.Youcanuseyourcomputers:

a)WriteashortPythoncodethatasksausertheirage.Onceyoudothat,decidewhethertoprintout“Yourageisanevennumber!”or“Yourageisanoddnumber!”dependingontheiranswer.b)Nowmodifyyourcodesothatitcandetectifsomeoneenteredanumberlessthan1astheirage.Ifso,printoutarejectionmessageandquit.Challenge:dothistwice:oncebyusingtheandoperatorandoncewithoutusingand(usingnested-ifstatements)

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ClassExerciseage=int(input("Howoldareyou?"))if(age%2==0):

print("Yourageisanevennumber!")else:

print("Yourageisanoddnumber!")

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ClassExerciseage=int(input("Howoldareyou?"))if(age%2==0)and(age>0):

print("Yourageisanevennumber!")elif(age%2!=0)and(age>0):

print("Yourageisanoddnumber!")else:

print("Youhaveenteredanillegalage!")

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Page 10: Loops in Python - GitHub PagesRepetition with a while loop • while condition: # executes over and over until a condition is False • While loops won’t run at all if condition

ClassExerciseage=int(input("Howoldareyou?"))if(age>0):

if(age%2==0): print("Yourageisanevennumber!")else: print("Yourageisanoddnumber!")

else:print("Youhaveenteredanillegalage!")

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Loops•  Sometimeswewanttobeabletorepeatapartoftheprograma

certainnumberoftimeswithoutbeingrepetitive–  Calleda“loop”

•  Soinsteadofsaying: print(“hello”) print(“hello”) print(“hello”)

Icansay: dothefollowing3times: print(“hello”)

•  Apopularwaytodothisiswith theforandthewhile commands.

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Repetitionwithaforloop•  for refin somelist: #blockofinstructions–refreferstocurrentobjectinlist #notethattheblockisallindented–  for,in,:–mandatoryparts–  ref–anameforreferringtoobjectsinthelist

•  Example:fornumbersin(0,1,2,3,4,5): print(numbers)

Thiswillprintoutthenumbers1thru5insequence

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OtherExamplesforxin(9,22,-77,1):

y=x+10print(y)

foryin("Hello","Mother","Hello","Father"):

print(x,"!!")n=0foritemin["UCSBLocation",(34.4140,-119.8489)]:

n=n+1print(n,item)

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WHATDOYOUTHINKTHESELOOPSPRINTOUT?

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Usingrangewithforloops•  Therange()built-infunctionprovidesahandylist•  Simplestuse:range(n)

–  Createsalistwithnitems[0, 1, 2, …n-1]

•  Example: fornumbersinrange(6): print(numbers)

Thiswillprintoutthenumbers1thru5insequence

(justlikethelastexample)

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OtherExamplesforxinrange(7):

print(x)foryinrange(2,9):

print(x-2)foriteminrange(5,-1,-1):

ifitem==0: print(item,"Blastoff!!")else: print(item)

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WHATDOYOUTHINKTHESELOOPSPRINTOUT?

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Repetitionwithawhileloop•  while condition: #executesoverandoveruntilaconditionisFalse

•  Usedforindefiniteiteration

–  Whenitisn’tpossibletopredicthowmanytimesaloopneedstoexecute,unlikewithforloops

•  Weuseforloopsfordefiniteiteration (e.g.,theloopexecutesexactlyntimes)

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Page 17: Loops in Python - GitHub PagesRepetition with a while loop • while condition: # executes over and over until a condition is False • While loops won’t run at all if condition

Repetitionwithawhileloop•  while condition: #executesoverandoveruntilaconditionisFalse

•  Whileloopswon’trunatallifconditionstartsoutasfalse

•  Whileloopsrunforeverifconditionneverbecomesfalse(i.e.ifitalwaysstaystrue)

•  Socaremustdoneindesigningthesesortofloops.

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Page 18: Loops in Python - GitHub PagesRepetition with a while loop • while condition: # executes over and over until a condition is False • While loops won’t run at all if condition

Applyingwhile Canbeusedforcounter-controlledloops:

n=500counter=0#(1)initializewhilecounter<n:#(2)checkconditionprint(counter*counter)counter=counter+1#(3)changestate

–  ButNOTEthatthisisadefiniteloop–easiertouseaforloop:forcounterinrange(500): …etc…

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ApplyingwhileThisisabetterapplicationexample–unlimiteddataentry:

AllGrades=0 #(1)initializegrade=int(input("entergradeorqtoquit:"))whilegrade!="q": #(2)checkcondition AllGrades=AllGrades+grades #processgrade grade=int(input("entergradeorqtoquit:"))#askagain

#Whileloophasended(noindentsafterhere),#nowyoucandootherstuff…print("Totalgradesis:",AllGrades)print("You'realldonenow!")

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YOURTO-DOsq  FinishreadingChapter5

q  We’llbediscussingloopsonWednesday

q  StartonHW4(duenextMONDAY)q  DoLab3(labtomorrow;turnitinbyFriday)

q  Don’tbikeangry!1/29/19 Matni,CS8,Wi19 20

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Loops ISYS 350. Three Types of Loops while loop do while loop for loop.

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1 Agenda - Loops while for for & while Nested Loops do-while Misc. & Questions.

1.6 Loops academy.zariba.com 1. Lecture Content 1.While loops 2.Do-While loops 3.For loops 4.Foreach loops 5.Loop operators – break, continue 6.Nested.

1.6 Loops academy.zariba.com 1. Lecture Content 1.While loops 2.Do-While loops 3.For loops 4.Foreach loops 5.Loop operators – break, continue 6.Nested.

while loops

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Loops (While and For)vlm1.uta.edu/.../lectures/08a_loops.pdf · while loops •A while loop is defined as follows: while (condition) { line 1 line 2 … line n } • condition is

Loops (While and For)vlm1.uta.edu/.../lectures/08a_loops.pdf · while loops •A while loop is defined as follows: while (condition) { line 1 line 2 … line n } • condition is

1 Agenda Summary of last class Loops Simple Loops WHILE Loops FOR Loops Records Cursors.

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Loops(2) do-while, forceng198.cankaya.edu.tr/uploads/files/ceng198 week6.pdf · Do While Loop do-while loop is the same as while loop except that the condition is checked at the end

Loops(2) do-while, forceng198.cankaya.edu.tr/uploads/files/ceng198 week6.pdf · Do While Loop do-while loop is the same as while loop except that the condition is checked at the end

while loops - Borenstein Lab

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Tutorial_ for Loops and While Loops - National Instruments

Tutorial_ for Loops and While Loops - National Instruments

7.3 The while loopaytugonan.cbu.edu.tr/YZM3217/Projects/python_week4.pdf · 7.3 The while loop In Python, while loops are constructed like so: while [a condition is True]: [do something]

7.3 The while loopaytugonan.cbu.edu.tr/YZM3217/Projects/python_week4.pdf · 7.3 The while loop In Python, while loops are constructed like so: while [a condition is True]: [do something]

1 Chapter 6 Looping. 2 Chapter 6 Topics l While Statement Syntax l Count-Controlled Loops l Event-Controlled Loops l Using the End-of-File Condition to.

1 Chapter 6 Looping. 2 Chapter 6 Topics l While Statement Syntax l Count-Controlled Loops l Event-Controlled Loops l Using the End-of-File Condition to.

More loops Horstmann Ch 7 continued.. The do-loop continue- condition ? loop-body statements next statement false true WHILE-LOOP continue- condition?

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Chapter 7 Loops - FTMS...PROG0101 Fundamentals of Programming 23 Loops DO-WHILE Loop • Like a while loop, a do-while loop is a loop that repeats while some condition is satisfied.

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Topic 15 Indefinite Loops - While Loops 15 Indefinite Loops - While Loops ... While loop flow chart 8The execution of a while loop can be depicted as ... – Print out the sum and

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More loops Linag, Chpt 3, pp 82-99. The do-loop continue- condition ? loop-body statements next statement false true WHILE-LOOP continue- condition? loop-body.

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