recognize gaps in a list of sequences of numbers, and group them

gaps.py

#!/usr/sbin/python
# Taken from Python examples: https://docs.python.org/2.6/library/itertools.html#examples
from operator import itemgetter
from itertools import groupby
data_list = [[1,3], [1, 2, 3], [3]]
for data in data_list:
	for k, g in groupby(enumerate(data), lambda ix :ix[0]-ix[1]):
	    print map(itemgetter(1), g)