Could someone explain this multidimensional list behaviour?

[Thomas Jensen]

lrl at ou.edu (L) wrote in 
news:e5f40188.0111222310.5001b6e2 at posting.google.com:

> Greetings from a long time java programmer jumping ship,
> 
> I'm not having trouble getting around this behavior:
> 
>>>> spam = [[0] * 3] * 3 spam [[0, 0, 0], [0, 0, 0], [0, 0, 0]]
>>>> spam[0][1] = 1
>>>> spam
> [[0, 1, 0], [0, 1, 0], [0, 1, 0]]
> 
> I was expecting after making the assignment to get this:
> [[0, 1, 0], [0, 0, 0], [0, 0, 0]]

[snip]

> So what is the easy way to allocate an n x n matrix with unique
> values?

There was a discussions very recently discussing this, but I was unable 
to find it :-)

>>> spam = [[0 for i in range(3)] for j in range(3)]
>>> spam[0][1] = 1
>>> spam
[[0, 1, 0], [0, 0, 0], [0, 0, 0]]

-- 
mvh
Thomas Jensen