In [30]: m =[ [0] * 3 ] * 3

In [31]: m
Out[31]: [[0, 0, 0], [0, 0, 0], [0, 0, 0]]

In [32]: m[0][0] = 1

In [33]: m
Out[33]: [[1, 0, 0], [1, 0, 0], [1, 0, 0]]

In [34]:

m = [[0 for x in range(3)] for y in range(3)]