list example

 a=[[10,20,30],[40,50,60]]

print(a)
[[10, 20, 30], [40, 50, 60]]

a[0]
[10, 20, 30]

a[1]
[40, 50, 60]

a[0][0]
10

a[1][2]
60

===================================================================

a=[[[10,20],[30,40]],[[50,60],[70,80]]]

print(a)
[[[10, 20], [30, 40]], [[50, 60], [70, 80]]]

a[0]
[[10, 20], [30, 40]]

a[1]
[[50, 60], [70, 80]]

a[0][0]
[10, 20]

a[0][0][0]
10

a[1][1]
[70, 80]

a[1][1][1]
80