code: def _organize_by_position(orig_file, cmp_file, chunk_size):
      
      with open(orig_file) as in_handle:
          reader1 = csv.reader(in_handle)
          positions = len(next(reader1)) - 1
      for positions in _chunks(range(positions), chunk_size):
          with open(orig_file) as orig_handle:
              with open(cmp_file) as cmp_handle:
                  orig_reader = csv.reader(orig_handle)
                  cmp_reader = csv.reader(cmp_handle)
                  for item in _counts_at_position(positions,
                          orig_reader, cmp_reader):
                      yield item
docs: Read two CSV files of qualities, organizing values by position.