why does the list of list replicate this way?

[hshivaraj]

a = [[]] * 10

a
[[], [], [], [], [], [], [], [], [], []]

a[0].append((1,2))

a
[[(1, 2)], [(1, 2)], [(1, 2)], [(1, 2)], [(1, 2)], [(1, 2)], [(1, 2)], [(1, 2)], [(1, 2)], [(1, 2)]]

Why does it replicate the values across the entire list? Bizarre

[Windspar]

Because list are reference. [[]] * 10 makes 10 reference copies.

a = [[] for x in range(10)]

[hshivaraj]

Thanks very much windspar.
That was as simple as that :)