雨课堂学堂在线学堂云《Object Oriented Programming(Python)（日照职业技术学院）》单元测试考核答案

第1题Pythonhasarichcollectionofthird-partylibraries.第2题TheexceptionsinPython2areusedinthesamewayasthoseinPython3.第3题PyCharmisacompleteandfreeIDEtool.第4题WhichofthefollowingoptionsisnotafeatureofPython.ASimpleandeasytolearnBFreeopensourceCObjectorientedDCompiledlanguage第5题WhichofthefollowingstatementsaboutPython2andPython3isincorrect.APython3defaultstoUTF-8encodingBTheformatoftheprintstatementinPython2andPython3hasnotchangedCPython2defaultstoASCIIencodingDTheusageoftheoperator"//"inPython2andPython3isconsistent第6题WhichofthefollowingstatementsaboutPythonnamingconventionsisincorrect.AModuleandpackagenamesshouldbeshortandalllowercaseBClassnamestypicallyuseuppercaselettersCConstantsareusuallynamedwithalluppercaselettersDCannotuseunderlineinfunctionname第7题Amongthefollowingoptions,()isavariablenamethatdoesnotcomplywiththespecifications.A_textB2cdCITCASTDHei_ma第8题Whichofthefollowingstatementsabouttheinput()andprint()functionsisincorrect.ATheinput()functioncanreceivedatainputfromthekeyboardBTheinput()functionreturnsastringtypedataCTheprint()functioncanoutputanytypeofdataDTheprint()functionoutputsdatathatdoesnotsupportlinebreaks第9题TherearetwowaysinwhichPythonprogramscanrun:____and____.正确答案：:interactive正确答案：:Filestyle第10题Pythonuniformlyuses____forindentation.正确答案：:4spaces第11题InPython,____isusedtorepresentasinglelinecomment.正确答案：:#第12题Using____and____inPythontorepresentmultiplelinesofcomments正确答案：:Threesinglequotationmarks正确答案：:Threedoublequotes第13题Pythonindentationcanmixtabsandspaces.第14题Pythoncanusemultilinecommentswiththreesinglequotesorthreedoublequotes.第15题Morecommentsarenotbetter.Forclearcode,thereisnoneedtoaddcomments.第16题Inordertoensuretheconsistencybetweentheprogramandtheproblem,aswellasthelong-termstableuseoftheprogram,peopledividetheprogramdevelopmentprocessintosixstages,namely:problemanalysis,boundarydivision,programdesign,programwriting,testingandcalling,upgradingandmaintenance.第17题Whetheritisasmall-scaleprogramthatsolvesthefourarithmeticoperationsoracomplexcontrolprogramusedbyspacecraft,theyallfollowtheoperationmodeofinputdata,processingdata,andoutputdata.第18题Variablenamesandclassnamesmustbemeaningfulandsinglelettersarestrictlyprohibited.第19题Variablenamescanusesystemkeywords.第20题Variablenamesshouldreflectthedatatypeandspecificmeaningofthevariableasmuchaspossible.第21题Python'snumbertypesincludeinteger,floating-point,complex,andBoolean.第22题Booleantypeisaspecialtypeofinteger.第23题ComplexnumbersinPythonconsistofrealandimaginaryparts.第24题ShapesinPythoncanberepresentedinbinary,octal,decimal,orhexadecimal.第25题Floatingpointtypecannotbecalculatedwithcomplexdata.第26题Usingslicingoperationstrings,thestepsizeofslicingcanonlybepositiveintegers.第27题Theoperator"=="inPythonisusedtodeterminewhethertwooperandsareequal.第28题Theoperator"="inPythonisusedtodeterminewhethertwooperandsareequal.第29题Theoperator"<>"inPythonisusedtodeterminewhethertwooperandsareequal.第30题Whichofthefollowingfunctionscanconvertanumericaltypetoastring.AComplex()BInt()CFloat()DStr()第31题WhichofthefollowingstatementsaboutPythonstringsisincorrect.AStringisadatatypeusedtorepresenttextBInPython,singlequotes,doublequotes,andtriplequotescanbeusedtodefinestringsCAsinglequotedstringcannotcontaindoublequotedcharactersDStringsdefinedusingtriplequotescancontainlinebreaks第32题Giventhevariablename="ZhangHao"andage=18,whichofthefollowingstringformattingoutputsisincorrectAPrint('Mynameis%s,Iam%dyearsoldthisyear'%(age,name))BPrint('Mynameis%s,Iam%dyearsoldthisyear'%(name,age))CPrint('Mynameis{},I'm{}yearsoldthisyear'format(name,age))DPrint(f'Mynameis{name},I'm{age}yearsoldthisyear')第33题Whichofthefollowingstatementsaboutstringoperationsiscorrect.AStringsupportsaddition,subtraction,multiplication,anddivisionoperationsBStringscanbeconcatenatedusingthe"+"symbolCStringscanbereplacedwithsubstringsusingthesplit()methodDStringscanusethestrip()methodtoremoveextraspacesonbothsides正确答案：BD第34题Givena=3andb=5,whichofthefollowingexpressionsyieldsanincorrectcalculationresult.AThevalueofa+=bis8BThevalueofa=bis-2CThevaluesofaandbare5DThevalueofa/bis0.6第35题Givena=2andb=8,whichofthefollowingexpressionsyieldsanincorrectcalculationresult.AThevalueofa%bis2BThevalueofa**bis256CThevalueofa/bis0DThevalueofa+=bis8第36题Givena=2andb=3,whichofthefollowingexpressionsyieldsanincorrectcalculationresult.Aa>TheresultofbisFalseBACA==bresultsinFalseDA=TheresultisTrue第37题Givena=10andb=20,whichofthefollowingexpressionshasanincorrectcalculationresult.AThevaluesofaandbare20BThevalueofaorbis20CThevalueofaorbis10DNotaresultisFalse第1题TheloopstatementsinPythonincludeforloopandwhileloop.第2题KeyifisusedinPythontorepresentconditionalstatements.第3题Onlystatementsthatmeettheconditionwillbeexecutedwhentheifconditionalexpressionistrue.第4题ThebreakandcontinuestatementsinPythoncanbeusedseparately.第5题If...elsestatementscanhandlemultiplebranchconditions.第6题Nestinginaforloopcanbeunderstoodascontainingaforloopstatementwithinaforloop.第7题ThewhileloopandforloopinPythonbothrepresentinfiniteloops.第8题ForloopsinPythondonotsupportnesting.第9题IfstatementsinPythondonotsupportnesteduse.第10题Pleasereadthefollowingprogram:a=1b=2c=3ifbA1,2,3B362C263D163第11题Pleasereadthefollowingprogram:x=0forxinrange(5):x+=1ifx=3:breakprint(x,end="")Theoutputresultoftheprogramis()A1B12C1,2,3D12345第12题Pleasereadthefollowingprogram:i=3j=5whileTrue:ifi<5:i+=iprint(i)breakelifj<1:j-=jprint(j)Runtheprogram,andtheoutputresultoftheprogramis()A8B2C6D0第13题Whichofthefollowingstatementsabouttheforloopisdescribedcorrectly.ATheforloopcantraverseiterableobjectsBForloopscannotbenestedforuseCTheforloopcannotbeusedwithanifstatementDTheforloopcannotcontrolthenumberoftimestheloopisexecuted第14题Whichofthefollowingstatementscanbreakoutoftheloopbody.AContinueBBreakCWhileDIf第15题Whichofthefollowingstatementscanendthisloopandcontinuetothenextloop.AContinueBBreakCWhileDIf第16题ThemodulesinPythonaredividedintobuilt-inmodules,custommodules,andthird-partymodules.第17题Modulescanbeimportedthroughthe"importmodule"and"frommoduleimportfunction/method".第18题ThepackageinPythonisadirectorycontaining__init__.py.第19题Whenusingthird-partymodules,itisnecessarytoinstalltheminadvance.第20题Apyfileisamodule.第21题The__init__.pyfileinthepackagestructurecannotbeempty.第22题Randomisabuilt-instandardlibraryinPythonthatcangeneraterandomdatausingfunctionswithinthelibrary.第23题TheOSmoduleprovidessystemleveloperations.第24题Therandom()functionintherandommodulecanonlygeneraterandomintegers.第25题Whenusingstandardmodules,itisnecessarytoinstalltheminadvance.第26题Moduleswithsimilarfunctionscanbeplacedinthesamepackage.第27题Standardmodulescanbeusedwithoutimport.第28题WhichofthefollowingstatementsaboutmodulesinPythoniscorrect.AOnlyPythonbuilt-instandardmodulescanbeusedintheprogramBOnlystandardmodulessupportimportCOnlyafterimportingthemodulecanthevariables,functions,andclassesinthemodulebeusedDCannotcustomizemodule第29题Whichofthefollowingmethodsaboutstandardmodulesisincorrect.AStandardmodulescanbeusedwithoutimportBTherandommodulebelongstothestandardmoduleCStandardmodulescanbeimportedthroughimportDThestandardmoduleisalsoa.pyfile第30题Whichofthefollowingimportmodulemethodsisincorrect.AImportrandomBFromrandomimportrandomCFromrandomimport*DFromrandom第31题Whichofthefollowingoptionscanrandomlygenerateaspecifiedrangeofintegers.ARamdom.random()BRandom.randint()CFromrandomimport*DRandom.uniform()第32题Whichofthefollowingstatementsaboutpackagesisincorrect.AThepackagecanbeimportedusingtheimportstatementBThepackagemustcontaina__int__.pyfileCModuleswithsimilarfunctionscanbeplacedinthesamepackageDThepackagecannotusefromImportMethodimport第33题Functionscanimprovecodereusability.第34题Globalvariablescanbeaccessedinallfunctions.第35题Thepositionalparametersofafunctionhavestrictpositionalrelationships.第36题Thedefaultparameterinafunctioncannotpassactualparameters.第37题Thefunctionwillbeexecutedimmediatelyafteritisdefined.第38题Variablescanbeaccessedbybackatanypositionintheprogram.第39题Globalvariablescanbedirectlyaccessedandmodifiedwithinanyfunction.第40题Afterthefunctionexecutioniscompleted,itsinternallocalvariableswillbereclaimed.第41题Whichofthefollowingstatementsaboutfunctionparametersisincorrect.AIfyoucannotdeterminethenumberofparametersthatneedtobepassedintothefunction,youcansetanindefinitelengthparameterforthefunctionBWhenusingkeywordparameterstopassarguments,itisnecessarytoassociateformalparameterswiththeargumentsCWhendefiningfunctions,defaultvaluescanbesetforparametersDTheindefinitelengthparameter*argscanpassanindefinitenumberofassociatedformalparameternamesasactualparameters第42题WhichofthefollowingstatementsaboutPythonfunctionsisincorrect.AArecursivefunctionisonethatcallsitsownfunctioninthefunctionbodyBAnonymousfunctionwithoutfunctionnameCAnonymousfunctionsarenodifferentfromfunctionsdefinedusingthekeyworddef第43题Readthefollowingprogram:numone=12defsum(numtwos):globalnumonenumone=90returnnumone+numtwoprint(sum(10))Runthecode,andtheoutputresultis()A102B100C22D12第44题Readthefollowingprogram:defmany_param(num'one,num_two,*args):print(args)many_param(11,22,33,44,55)Runthecode,andtheoutputresultis().A(11,22,33)B(22,33,44)C(33,44,55)D(22,33,44,55)第45题Pythonusesthe()keywordtodefineananonymousfunction.AFunctionBFuncCDefDLambda第46题Pythonusesthe()keywordtodefineafunction.AFunctionBFuncCDefDLambda第47题Pythonusesthe()keywordtodeclarelocalvariablesasglobalvariables.AFunctionBGlobalCNonlocalDLambda第48题Pythonusesthe()keywordtomodifyvariablesdeclaredinnestedscopeswithinalocalvariablescope.AFunctionBGlobalCNonlocalDLambda第49题Thefunctionimplementedbythefollowingcodeis():deffun(num):ifnum==1:return1else:returnnum*fun(num-1)AN!BTheHanoiTowerProblemCFibonaccisequenceDSumof1ton第50题Using()inPythoncanformescapecharacters.A/B\C$D%第51题Whichofthefollowingoptionsisusedtoformatastring.A%BFormat()C+D#正确答案：AB第52题Whichofthefollowingmethodscanconvertalllettersinastringtouppercase.AUpper()BLower()CTitle()DCapitalize()第53题Whichofthefollowingmethodscanconvertalllettersinastringtolowercase.AUpper()BLower()CTitle()DCapitalize()第54题Whichofthefollowingoptionsbelongstothestring.A1BPythonC@123D1'.23正确答案：ABC第55题Stringscanbedefinedusingsinglequotes,doublequotes,andtriplequotes.第56题ThecollectionofdictionarykeyscanbeviewedthroughPython'sbuilt-inmethodkeys().第57题Callingtheitems()methodallowsyoutoviewalltheelementsinthedictionary.第58题ThecommoncharacteristicsofmutableandimmutablesetsinPythonaredisorderandnonrepeatableelements.第59题Createalistusingthebuilt-inlistfunction.第60题TheelementsofalistinPythoncanbeaccessedthrougheitherindexingorslicing.第61题Usethebuilt-intuplefunctiontocreateanancestor.第62题Thekeysinthedictionaryareunique.第63题Theelementsinthecollectionareunordered.第64题Theelementsinthedictionarycanbeaccessedthroughindexing.第65题Theelementsinthecollectioncanbeduplicated.第66题Alistcanonlystoredataofthesametype.第67题Tuplessupportoperationstoadd,delete,andmodifyelements.第68题Theindexoftheliststartsfrom1.第69题Ifthereisonlyoneelementinatuple,thentheremustbeacommaafterthatelement.第70题Whichofthefollowingmethodscanobtainallthekeysinthedictionary.AKeys()BValue()CList()DValues()第71题Whichofthefollowingmethodscanobtainallvaluesinthedictionary.AKeys()BValue()CList()DValues()第72题Callingthe()methodcanviewallelementsinthedictionary.AItems()BKeys()CValue()DList()第73题Usethe()functiontocreatealist.AList()BTuple()CDict()DSet()第74题Usethe()functiontocreateacollection.AList()BTuple()CDict()DSet()第75题Usethe()functiontocreateatuple.AList()BTuple()CDict()DSet()第76题TheelementsofalistinPythoncanbeaccessedthrougheither___or___methods.AindexBsectionCchoiceDIntercept正确答案：AB第77题Readthefollowingprogram:lan_info={1:"Python",2:"Java",3:"PHP"}lan_info.update({3:"C++"})print(lan_info)Runtheprogram,andtheoutputresultis().A{1:'Python',2:'Java',3:'PHP'}B{1:'Python',2:'Java',3:'C++'}C{3:'C++',1:'Python',2:'Java'}D{1:'Python',2:'Java'}第78题Whichofthefollowingmethodscannotdeleteelementsfromthedictionary.AClear()BRemove()CPop()DPopitem()第79题Readthefollowingprogram:set_1={'a','c','b','a'}print(len(set_1))set_1.add('d')print(len(set_1))Runtheprogram.Whichofthefollowingoutputresultsiscorrect.A45B34C23D25第80题Whichofthefollowingstatementscancorrectlycreateadictionary.ATest_one=()BTest_two={1:'A'}CTest_three=dict('a')DTest_four=dict{1:'A'}第81题Whichofthefollowingmethodscanarrangelistelements.ASort()BReverse()CMax()DList()ProjectThree第1题Thefirstparameterinthe__init__()methodisalways().ASefBSelfCCLSDempty第2题Aclasscanonlycreateoneinstantiatedobject.第3题Theconstructionmethodisautomaticallycalledwhencreatinganobject.第4题WhichofthefollowingoptionsisnotareservedwordforPythonlanguage.ADoBPassCExceptionDWhile第5题Pythondoesnotsupportmultipleinheritance.第6题Pythonautomaticallycallsthedestructorwhendeletinganobject.第7题Pythonprivatememberscanonlybeaccessedinternallyandcannotbeaccessedfromobjects.第8题Staticvariablesandstaticmethodsbelongtoinstancesoftheclass.第9题Staticmethodscanbeaccesseddirectlywithouttheneedforcallingwithaclassnameorstaticmethodname.第10题Staticmethodscandirectlymanipulateclassstaticvariables.第11题Classmethodscanmanipulateclassstaticvariables.第12题Staticmethodsdonotrequirethekeywordself.第13题Bothstaticmethodsandclassmethodscanbecalledbyobjects.第14题Readthefollowingprogram:li_one=['p','c','q','h']li_two=['c']li_one.extend(li_two)li_one.insert(2,'n')print(li_one)Runtheprogram,andthecorrectoutputis().A['p','c','n','q','n','c']B['o','p','c','q','h','n']C['p','c','n','q','h','c']D['o','p','n','q','h','c']第15题Whichofthefollowingstatementsforcreatingtuplesiscorrect.ATu_one=tuple('1','2')BTu_two=(q)CTu_one=('on',)DTu_four=tuple(3,5)第16题ThecombineddatatypesinPythoninclude().ASequencetypeBCollectiontypeCmappingtypeDArraytype正确答案：ABC第17题Whichofthefollowingstatementsarecorrectforcombineddatatypes.ATheindexofasequencestartsfrom0BSequencesinPythonsupportbidirectionalindexingCMappingtypesstoredataintheformofkeyvaluepairsDTheelementsinthesetcanberepeated正确答案：ABC第18题InPython,thecorrectwaytocreatealistis().ACreatealistusingsquarebrackets[]BCreatealistusingcurlybraces{}CCreatealistusingthelist()functionDCreatealistusingparentheses()正确答案：AC第19题Alistisaniterableobjectthatcanbeaccessedonebyoneusingthefor...in...statement.第20题Whichofthefollowingmethodscanaddelementstothelist.AAppend()BExtend()CSort()DInsert()正确答案：ACD第21题Whichofthefollowingmethodscandeletelistelements.ADelstatementBRemove()CPop()DClear()正确答案：ABCD第22题ThecorrectstatementaboutsetsinPythonis().ATheelementsinthesetareunorderedBTheelementsinthesetareuniqueCTheelementsinthecollectioncanbedynamicallyaddedorremovedDOnceacollectioniscreated,itcannotbechanged正确答案：ABCProjectFour第1题Thefile'wb'modereferstowritingonlyintextmode.第2题Thefile'r+'modecanbereadandwritten,butthefilemustexist.第3题Thefile'w+'modecanbereadandwritten,andthefileshouldbecreatedfirstwhenitdoesnotexist.第4题Whatistheresultofrunningthefollowingcode?()importmathprintmath.floor(5.5)A5B5C5.5D6第5题Whatistheresultofrunningthefollowingcode?()foriinrange(2):print(i)A0B01C012D12第6题Whichofthefollowingareobject-orientedfeatures.AencapsulationBinheritCpolymorphicDcomposite正确答案：ABC第7题WhatisthecorrectstatementaboutPythonclasses.ATheinstancemethodofaclassmustcreateanobjectbeforeitcanbecalledBTheinstancemethodofaclassmustbecalledbeforecreatinganobjectCClassmethodscanbecalledusingobjectsandclassnamesDStaticmethodsofaclasscanbecalledusingtheclassnameandobject正确答案：ACD第8题WhichofthefollowingPythoncanstartnormally.ASpellingerrorsBIncorrectexpressionCIndenterrorDManuallythrowingexceptions第9题Thecorrectstatementaboutanomaliesis().AThrowinganexceptionintheprogramtoterminatetheprogramBThrowingexceptionsinaprogramdoesnotnecessarilyterminatetheprogramCSpellingerrorscancauseprogramterminationDIndentingerrorscancauseprogramtermination第10题WhichofthefollowingisnotavalididentifierinPython.AInt32B40XLCSelfD__Na__第11题Pythondoesnotsupportdatatypessuchas().ACharBIntCFloatDList第12题InPython,toaddalinebreaktoastring,whichcharactercombinationcanbeused.A\AB\NC\QD\X第13题InPython,theresultof3**2is().A3B6C9D12第14题InPython,addanelementmbetweenelementsaandbintheliststrs=['a','b','c'],andthecorrectoneis().AStrs.add(0,'m')BStrs.add(1,'m.)CStrs.insert(0,'m.)DStrs.insert(1,'m.)第15题InPython,thecorrectwaytouserange()toobtainnumbers1-5is().ARange(0,5)BRange(1,5)CRange(1,6)DRange(0,6)第16题InPython,use()toobtaintheminimumvalueinalist.AMinBMaxCCountDSum第17题Pythonreferstonumberswithdecimalpointsas().AdecimalBfractionCFixed-pointnumberDFloatingpointnumber第18题InPython,theoutermostlayerofthedictionaryuses().A()EncloseB[]EncloseitCEnclose{}DBringitup第19题InPython,thefunctionthatcausesaprogramtopauseandwaitfortheusertoinputsometextis().AInput()BOutput()CScanf()DPrint()第20题WhichkeywordinPythoncanimportamodule.AImportBSetCInputDFrom第21题InPython,theresultoftheoperationof(2+3)*4is().A16B17C19D20第22题ThecorrectusageofcommentsinPythonis().A#ThisisacommentB//ThisisacommentCThisisacommentD/*Thisisacomment*/第23题ThefileextensionforPythonprogramsis().A.txtB.libC.llD.py第24题InthePythonlanguage,theflagforacodesnippetis().AEnclosewith{}BAddasemicolonattheendCIndentedlinesofcodeDAdd"\n"tothestatement第25题InPython,listarr=[],usethelen(arr)methodtoobtainthelengthoflistarras().A-2B-1C0DNull第26题InPython,definingfunctionsrequirestheuseofthekeyword().ADefBDefineCIfdefDIfndef第27题Theresultof"ab"+"c"*2is().AAbc2BAbcabcCAbccDAbabcc第28题ThebestmethodtoimplementamultibranchselectionstructureinPythonis().AIfBIf--elseCIf--elif--elseDIf--elseIf--else第29题Themostmatchingfunctionofthetry--exceptstructureinPythonis().AHandlingexceptionsBAttempttoexecutePythonstatementsCAttempttowritedatatothedatabaseDAttemptingtoresolvecodeerrors第30题InPython,thepoweroperatoris().A*B**C/D%第31题ThemethodtoobtainthelengthofthestringsinPythonis().As.Len()Bs.LengthCLen(s)DLength(s)第32题Thepurposeofthestringfunctionstrip()is().ASplittingstringsintolistsbasedonspecifiedcharactersBConnecttwostringsequencesCRemovespacesonbothsidesofthestringorspecifycharactersDReplacespecificcharactersinastring第33题Beforereadingorwritingafile,whichofthefollowingmethodsisneededtocreateafileobject.ACreateBFolderCFileDOpen第34题InPython,commonloopsinclude().ADowhileBWhileCForDFor-loop正确答案：BC第35题Thereisastringstr01="ABCDEFG".Ifyouwanttoextractthecharacter"E",whichofthefollowingiscorrect.AStr01[4]BStr01[5]CStr01[-2]DStr01[-3]正确答案：AD第36题ThecorrectwaytoidentifymultilinecommentsinPythonis().AAnnotatecontentBCommentcontentC/*Annotationcontent*/D&Lt--AnnotationContent-->正确答案：AB第37题ThepossibleresultsoftheabovePythonstatementforimportrandomprint(random.randint(50100))are().A55B66C77D100正确答案：ABCD第38题ThecorrectkeywordforthepropertiesoftheListsetis().AOrderedBvariableCRepeatableDKeyvaluestoragestructure正确答案：ABC第39题Whenusingopentoreadtextfiles,whichfunctionsareusedtoreadfiles.AReadfile()BRead()CReadlines()DReadline()正确答案：BCD第40题Whenusingopentowritetextfiles,whichfunctionsareusedtowritefiles.AWritefile()BWrite(str)CWritelines()DWriteline()正确答案：BCProjectFive第1题InPython'sexceptionhandlingstructure,therearethreekeywords,namely().ATryBExcpetCCatchDFinally正确答案：ABD第2题Createaclassusingthe()keywordinPython.AClassBDefCTryDLamda第3题ThecorrectobjectstatementfordefiningtheCarclassis().ACar=CarBCar=Car()CNewCarDCar=newCar()第4题InPython,thecorrectstatementtocreatetheStudentclassinheritingthePersonclassis().AStudentextendPersonBClassStudent(Person):CClassStudentextendPersonDClassStudent第5题Subclasscannotoverridemethodsofparentclass.第6题Byinheritingtheparentclassfromthesubclass,allmethodsandpropertiesoftheparentclasscanbeused.第7题Subclasscannotinheritprivatepropertiesandmethodsfromparentclass.第8题Usethe()functiontocreatealist.AList()BTuple()CDict()DSet()第9题Usethe()functiontocreateacollection.AList()BTuple()CDict()DSet()第10题Usethe()functiontocreateatuple.AList()BTuple()CDict()DSet()第11题TheelementsofalistinPythoncanbeaccessedthrougheither___or___methods.Aindex