how to make a nested list

[Chris Angelico]

On Fri, Sep 16, 2011 at 8:02 AM, Vlastimil Brom
<vlastimil.brom at gmail.com> wrote:
> Besides the above sugestions to correct the nested list approach,
> if you need to set and access the data at the given "coordinates" you
> could also use a nested defaultdict...

The defaultdict is efficient for a sparse matrix, but I suspect that
it'd be rather worse if you use all the elements.

ChrisA