Python многоуровневое понимание списка
>>> [ y for x in non_flat if len(x) > 2 for y in x ]
[1, 2, 3, 4, 5, 6]
Prickly Peacock
>>> [ y for x in non_flat if len(x) > 2 for y in x ]
[1, 2, 3, 4, 5, 6]
>>> [y for x in non_flat for y in x]
[1, 2, 3, 4, 5, 6, 7, 8]