code: def _init_data_line(self, fnc, lnum, line):
          
          fld = re.split(self.sep, line)
          # Lines may contain different numbers of items.
          # The line should have all columns requested by the user.
          if self.usr_max_idx < len(fld):
              self.convert_ints_floats(fld)
              fnc(fld)
          else:
              for fld in enumerate(zip(self.hdr2idx.keys(), fld)):
                  print(fld)
              for hdr in self.hdrs_usr:
                  print(hdr)
              print('# ITEMS ON A LINE:', len(fld))
              print('MAX USR IDX:', self.usr_max_idx)
              raise Exception("ERROR ON LINE {} IN {}".format(lnum+1, self.fin))
docs: Process Data line.