python - How to merge two columns together in Pandas -

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 continuous , 2 last columns merged one. suggestions?

you looking pd.melt.

suppose have dataframe

>>> df    date item1 item2 0  1975         b 1  1976     b     c 2  1977     b     3  1977         b 4  1978     c     d 5  1979     e     f 6  1980         f  [7 rows x 3 columns] 

now use this:

pd.melt(df, id_vars='year')['year','value'] 

to need.

>>> pd.melt(df, id_vars='date')[['date','value']]     date value 0   1975     1   1976     b 2   1977     b 3   1977     4   1978     c 5   1979     e 6   1980     7   1975     b 8   1976     c 9   1977     10  1977     b 11  1978     d 12  1979     f 13  1980     f  [14 rows x 2 columns]