terminal_split.py

def terminal_split(items, is_terminal):
    SENTINAL = object()
    ret = [[]]
    for item, next_item in izip_longest(items, items[1:], fillvalue=SENTINAL):
        ret[-1].append(item)
        if next_item is not SENTINAL and is_terminal(item) and not is_terminal(next_item):
            ret.append([])
    return ret

def is_terminal(x):
    return x == 2

self.assertEqual(terminal_split([1, 1, 2, 1, 1], is_terminal), [[1, 1, 2], [1, 1]])
self.assertEqual(terminal_split([1, 1, 2, 2, 1, 1], is_terminal), [[1, 1, 2, 2], [1, 1]])
self.assertEqual(terminal_split([1, 2, 2, 1, 2], is_terminal), [[1, 2, 2], [1, 2]])
self.assertEqual(terminal_split([2, 2], is_terminal), [[2, 2]])