gistfile1.py

turnover.columns = [x[-4:] if x.startswith('turnover') 
                    else x 
                    for x in turnover.columns.values]
turnover = pd.melt(turnover,id_vars=['bvd_id'],var_name='year',value_name='turnover')
turnover.year = turnover.year.astype('int')
turnover.turnover = [np.nan if x == 'n.a.' 
                    else x 
                    for x in turnover.turnover]
turnover.turnover = [str(x).replace(',','') if x != np.nan 
                    else x 
                    for x in turnover.turnover]