absolute newbie: divide a list into sublists (nested lists?) of fixed length

[ergconcepts at googlemail.com]

Hi,
I have a list looking like

[ 0.84971586,  0.05786009,  0.9645675,  0.84971586,  0.05786009,
0.9645675, 0.84971586,  0.05786009,  0.9645675,  0.84971586,
0.05786009,  0.9645675]

and I would like to break this list into subsets of fixed length (say,
three elements), i.e. to convert the list into a form such as the one
generated by the following example code which I have found:

>>>import numpy
>>>s = numpy.random.random((3,3))
>>>s
array([[ 0.11916176,  0.96409475,  0.72602155],
       [ 0.84971586,  0.05786009,  0.96456754],
       [ 0.81617437,  0.845342  ,  0.09109779]])

How can I create such a 2d array (i.e., something like a symmetric
matrix) from my data?

Thanks in advance,

Bernard

PS: Note that the numpy import is not important here, it is just the
structure of the data that matters..