Get an clean data from Api in python

Hi, I'm introducing the following code to get the data via api. There are many row that are empty. There will be some code that I can put so that the empty data is put by N.A and separated by ","

ek.get_timeseries(['AGR.BA','ALU.BA','APBR.BA','AUS.BA','HI.BA','MA.BA','BPAT.BA','BYMA.BA',
'CAMb.BA','CAO.BA','CARC.BA','CAU.BA','CEC.BA','CEL.BA','CEPU.BA','CLA.BA',
'COL.BA','COM.BA','CON.BA','CPS.BA','CRE.BA','CVH.BA','DOM.BA','DYC.BA',
'ECO.BA','EDLH.BA','EDN.BA','EDSH.BA','EMD.BA','ESM.BA','FER.BA','FIP.BA',
'FRA.BA','GAR.BA','GBA.BA','GFG.BA','GRM.BA','HARG.BA','HAVH.BA','INA.BA',
'INR.BA','INU.BA','INVJ.BA','IRCP.BA','IRS.BA','LED.BA','LOMA.BA','LON.BA',
'MERA.BA','MET.BA','MIR.BA','MOL.BA','MOLA.BA','MOR.BA','OEST.BA','PAM.BA',
'PAT.BA','PETR.BA','PGR.BA','POL.BA','PSU.BA','QUI.BA','REP.BA','RICH.BA',
'RIG.BA','RIO.BA','ROS.BA','SEI.BA','SMI.BA','STD.BA','SUPV.BA','TEC2.BA',
'TEF.BA','TENA.BA','TGLT.BA','TGNC.BA','TGS2.BA','TRA.BA','TXAR.BA','VAL.BA',
'YPFD.BA','YPFD.BA'], start_date='2000-01-01' , end_date='2018-01-01')

df.to_csv('galicia_2016_20128.csv')