i have data: 1975,a,b 1976,b,c 1977,b,a 1977,a,b 1978,c,d 1979,e,f 1980,a,f i want have two-column list of years , items, so: 1975,a 1975,b ... i have code: import pandas # set column names colnames=['date','item1','item2'] # read csv adding column names data = pandas.read_csv('/users/simon/dropbox/work/datasets/lagtest.csv', names=colnames) # create dataframe info on dates first column datelist1 = data[['date', 'item1']] # create dataframe info on dates first column datelist2 = data[['date', 'item2']] bigdatelist = datelist1.append(datelist2) print bigdatelist but gives me this: date item1 item2 0 1975 nan 1 1976 b nan 2 1977 b nan 3 1977 nan 4 1978 c nan 5 1979 e nan 6 1980 nan 0 1975 nan b 1 1976 nan c 2 1977 nan 3 1977 nan b 4 1978 nan d 5 1979 nan f 6 1980 nan f i want line numbering conti...