ayende.py

unsorted = {1, 59, 12, 43, 4, 58, 5, 13, 46, 3, 6}
sorted_list = sorted(unsorted)
list_length = len(sorted_list)
if list_length < 2:
    print sorted_list
current = [sorted_list[0]]
for index in xrange(1, list_length):
    if sorted_list[index - 1] + 1 == sorted_list[index]:
        current += [sorted_list[index]]
    else:
        print current, ',',
        current = [sorted_list[index]]
    if index + 1 == list_length:
        print current