>>> list(itertools.groupby('LLLLAAGGG'))
[('L', <itertools._grouper object at 0x109cf0208>), ('A', <itertools._grouper object at 0x109cf0128>), ('G', <itertools._grouper object at 0x109cf0240>)]
>>> for char, group in itertools.groupby('LLLLAAAGG'):
...     print(char, '->', list(group))
...
L -> ['L', 'L', 'L', 'L']
A -> ['A', 'A', 'A']
G -> ['G', 'G']
>>> animals = ['duck', 'eagle', 'rat', 'giraffe', 'bear','bat', 'dolphin', 'shark', 'lion']
>>> animals.sort(key= len)
>>> animals
['rat', 'bat', 'duck', 'bear', 'lion', 'eagle', 'shark', 'giraffe', 'dolphin']
>>> for length, group in itertools.groupby(animals, len):
...     print(length, '->', list(group))
...
3 -> ['rat', 'bat']
4 -> ['duck', 'bear', 'lion']
5 -> ['eagle', 'shark']
7 -> ['giraffe', 'dolphin']
>>> for length, group in itertools.groupby(reversed(animals), len):
...     print(length, '->', list(group))
...
7 -> ['dolphin', 'giraffe']
5 -> ['shark', 'eagle']
4 -> ['lion', 'bear', 'duck']
3 -> ['bat', 'rat']
>>>