Question

I need a function that accepts a list of two element tuples and returns these tuples grouped in lists where the second elements of the tuples are equal, and the original sequence order is kept. For instance,

>>> seq = [(0, 1), (1, 2), (2, 2), (3, 2), (4, 1), (5, 3), (6, 3), (7, 2)]
>>> split_repeated(seq)
[[(0, 1)], [(1, 2), (2, 2), (3, 2)], [(4, 1)], [(5, 3), (6, 3)], [(7, 2)]]

If I flat the result I must get original sequence:

>>> itertools.chain.from_iterable(split_repeated(seq)) == seq
True

Answer 1

>>> seq = [(0, 1), (1, 2), (2, 2), (3, 2), (4, 1), (5, 3), (6, 3), (7, 2)]
>>> from itertools import groupby
>>> from operator import itemgetter
>>> [list(items) for key,items in groupby(seq,key=itemgetter(1))]
[[(0, 1)], [(1, 2), (2, 2), (3, 2)], [(4, 1)], [(5, 3), (6, 3)], [(7, 2)]]