There is a df Pandas dataframe: date av_temp deviations country 1 1743-12-01 NaN NaN Åland 2 1744-01-01 NaN NaN Åland 3 1744-02-01 NaN NaN Åland 4 1744-03-01 NaN NaN Åland 9 1744-08-01 NaN NaN Åland Create a new column year from date in which you convert all date values to years. Example: 1744-01-01 Date column: 1744

df = pd.DataFrame({'date': ['1743-12-01', '1744-01-01', '1744-02-01', '1744-03-01', '1744-08-01'],
                   'av_temp': [0, 10, 20, 30, 40],
                   'deviations': [0, 10, 20, 30, 40],
                   'country': ['Åland', 'Åland', 'Åland', 'Åland', 'Åland']
                  })