Reverting from multiindex to single index dataframe in pandas

Question

                       NI
YEAR MONTH datetime        
2000 1     2000-01-01   NaN
           2000-01-02   NaN
           2000-01-03   NaN
           2000-01-04   NaN         


        

Answer 1

Another simple way would be to set columns for dataframe

consolidated_data.columns=country_master

ref: https://riptutorial.com/pandas/example/18695/how-to-change-multiindex-columns-to-standard-columns