Indexing list of lists

[Peter Otten]

Hilde Roth wrote:

> This may have been asked before but I can't find it. If I have
> a rectangular list of lists, say, l = [[1,10],[2,20],[3,30]], is
> there a handy syntax for retrieving the ith item of every sublist?
> I know about [i[0] for i in l] but I was hoping for something more
> like l[;0].

If efficiency is not an issue and/or you need 
[item[index] for item in theList] for more than one index at a time, you can
do:

>>> s = [[1,2],[3,4]]
>>> t = zip(*s)
>>> t
[(1, 3), (2, 4)]
>>> t[1]
(2, 4)
>>>

This creates a transposed (?) copy of the "matrix". The side effect of
creating tupples instead of inner lists should do no harm if you need only
read access to the entries.

Peter