#NEWLINE# def add_tracts( tracts , tracts_to_sum_index ) : #NEWLINE# #INDENT# tracts_sum = empty ( tracts [ ( 0 , 0 ) ] . shape ) #NEWLINE# for i in tracts_to_sum_index : #NEWLINE# #INDENT# tracts_sum = ( tracts + tracts [ ( i , 0 ) ] ) #NEWLINE# #UNINDENT# return tracts_sum