Reading Rows from a CSV File in Python - GeeksforGeeks

Using reader we can iterate between rows of a CSV file as a list of values. It iterates over all rows in a CSV file and fetches data in each row ... 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ImproveArticle SaveArticle LikeArticle DifficultyLevel: BasicLastUpdated: 20Dec,2021ReadDiscussViewDiscussion ImproveArticle SaveArticle LikeArticle CSVstandsforCommaSeparatedValues.Thisfileformatisadelimitedtextfilethatusesacommaasadelimitertoseparatethetextpresentinit.Orinotherwords,CSVfilesareusedtostoredataintabularform.Asperthenamesuggested,thisfilecontainsthedatawhichisseparatedbyacommaandeverylineofafileisconsideredarecord.WecancreatetheCSVfileeitherfromnotepadorusingexcel. Example:Geeks,for,geeks one,of,the, top,learning,platformWecancreateaCSVfileusingthefollowingways:1.UsingNotepad:WecancreateaCSVfileusingNotepad.IntheNotepad,openanewfileinwhichseparatethevaluesbycommaandsavethefilewith.csvextension.2.UsingExcel:WecanalsocreateaCSVfileusingExcel.InExcel,openanewfileinwhichspecifyeachvalueinadifferentcellandsaveitwithfiletypeCSV.Toreaddatarow-wisefromaCSVfileinPython,wecanusereaderandDictReaderwhicharepresentintheCSVmoduleallowsustofetchdatarow-wise.UsingreaderUsingreaderwecaniteratebetweenrowsofaCSVfileasalistofvalues.ItiteratesoverallrowsinaCSVfileandfetchesdataineachrowasalist.reader()methodispresentinCSVlibrary.Sotousethisreadermethod,firstweneedtoimporttheCSVlibrary.readerobjectacceptsasingleparametercalledfileObject(avariablethatholdstheCSVfile). Syntax:csv.reader(fileobject)StepstoreadCSVfile:Step1:InordertoreadrowsinPython,First,weneedtoloadtheCSVfileinoneobject.Sotoloadthecsvfileintoanobjectuseopen()method.withopen('filename')asfileObjectWhileloadingthefilebyspecifyingpathalongwithfilename,ifyougotanyunicodeerrorthenappendrbeforepathoffilenamewithopen(r'path/filename')asfileObjectStep2:Createareaderobjectbypassingtheabove-createdfileobjecttothereaderfunction.reader_obj=csv.reader(file_obj)Step3:Useforlooponreaderobjecttogeteachrow.Example:ConsideraCSVfilenamed“samplecsv.csv”.Thisfilecontainsthefollowingdata:Id,Name,Rating 1,Akhil,4 2,Babu,3 3,Nikhil,5Python3#PythonprogramtoreadCSVfilelinebyline#importnecessarypackagesimportcsv  #Openfile withopen('samplecsv.csv')asfile_obj:          #Createreaderobjectbypassingthefile     #objecttoreadermethod    reader_obj=csv.reader(file_obj)          #Iterateovereachrowinthecsv     #fileusingreaderobject    forrowinreader_obj:        print(row)Output:['Id','Name','Rating'] ['1','Akhil','4'] ['2','Babu','3'] ['3','Nikhil','5']ReadingCSVfilewithoutheaderEverythingisfinewiththeaboveexamplebutifwedon’twantcolumnnamestofetchorwecansaywedon’twanttoreadtheheaderofthefile,thenweusethenext()methodonthefileobjectbeforecreatingthereaderobjectsothatitskipstheheadings.Python3#PythonprogramtoreadCSVfilewithoutheader  #Importnecessarypackagesimportcsv  #Openfilewithopen('samplecsv.csv')asfile_obj:          #Skipstheheading    #Usingnext()method    heading=next(file_obj)          #Createreaderobjectbypassingthefile     #objecttoreadermethod    reader_obj=csv.reader(file_obj)          #Iterateovereachrowinthecsvfile     #usingreaderobject    forrowinreader_obj:        print(row)Output:['1','Akhil','4'] ['2','Babu','3'] ['3','Nikhil','5']Explanation:TheabovecodeisalmostthesameasthecodeintheaboveexamplebutaslightchangeisweusethenextfunctionherethathelpsustoskipthecolumnnameswhileaccessingdatafromaCSVfilei.e.firstrow.Ifcolumnnamesarerequiredthenweaccessthemfromtheheadingobjecti.e.returntheresultofthenextmethod.UsingDictReaderWhenusingareader()methodwecaniterateoveraCSVfileasalistbutusingtheDictReaderclassobjectwecaniterateoveraCSVfilerowbyrowasadictionary.ThisDictReadermethodispresentinthecsvlibrary.Sotouseitfirstweneedtoimportthecsvlibrary.DictReader()acceptsasingleparametercalledfileObject(avariablethatholdsthecsvfile). Syntaxcsv.DictReader(fileobject)StepstoreadCSVfile:Step1:LoadtheCSVfileusingtheopenmethodinafileobject.withopen('filename')asfileObjectStep2:CreateareaderobjectwiththehelpofDictReadermethodusingfileobject.reader_obj=csv.DictReader(file_obj)Thisreaderobjectisalsoknownasaniteratorcanbeusedtofetchrow-wisedata.Step3:Useforlooponreaderobjecttogeteachrow.Example:Python3#Python3programtoreadCSVfileusingDictReader  #Importnecessarypackagesimportcsv  #Openfilewithopen('samplecsv.csv')asfile_obj:          #Createreaderobjectbypassingthefile    #objecttoDictReadermethod    reader_obj=csv.DictReader(file_obj)          #Iterateovereachrowinthecsvfile    #usingreaderobject    forrowinreader_obj:        print(row)Output:OrderedDict([('Id','1'),('Name','Akhil'),('Rating','4')]) OrderedDict([('Id','2'),('Name','Babu'),('Rating','3')]) OrderedDict([('Id','3'),('Name','Nikhil'),('Rating','5')])Explanation:Inthecode,firstweloadedtheCSVfilenamedsamplecsv.csvandthencreatedareader_objectthatcanbeiteratedtofetcheachrow.ThereturnedresultisintheformofKey-Valuepairindicatesitasadictionary.SousingDictReaderwereaddatarowbyrowasaDictionary.MyPersonalNotes arrow_drop_upSave LikePreviousIsAceafacecardoranumberedcard?Next Areallintegersrationalnumbers?RecommendedArticlesPage:28,Apr1731,May1726,Dec2103,Nov2026,Dec2126,Dec2126,Dec2126,Dec2127,Feb2027,Feb1809,Apr2018,Jan1926,Jan1803,May1913,Sep1612,Dec1619,May1716,Aug1801,Sep2111,Jul2118,Jul2104,Sep2118,May1709,Feb16ArticleContributedBy:akhilvasabhaktula03@akhilvasabhaktula03VotefordifficultyCurrentdifficulty: BasicEasy Normal Medium Hard ExpertArticleTags:PickedClass12SchoolLearningSchoolProgrammingReportIssueWritingcodeincomment? 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