compress_integer_list.py

def append_range(ranges, current_range_start, current_range_end):
  if current_range_start == current_range_end:
    ranges.append(current_range_start)
  else:
    ranges.append((current_range_start, current_range_end))

def compress_list_of_integers(ints):
  if len(ints) == 0:
    return []
  ranges = []
  current_range_start = ints[0]
  current_range_end = None
  for value in ints:
    if current_range_end == None or value == current_range_end + 1:
      current_range_end = value
    else:
      append_range(ranges, current_range_start, current_range_end)
      current_range_start = value
      current_range_end = value
  append_range(ranges, current_range_start, current_range_end)
  return ranges

print compress_list_of_integers([1,2,3,4,5,10,11,12,13,14,21,55,56,57])
# => [(1, 5), (10, 14), 21, 23, 28, (55, 57)]