Как проверить, вложен ли список или нет

In [11]: a = [1, 2, 3]

In [12]: b = [[1], [2], [3]]

In [13]: any(isinstance(i, list) for i in a)
Out[13]: False

In [14]: any(isinstance(i, list) for i in b)
Out[14]: True
Darkstar