# Sorting (deeply) nested lists

Discussion in 'Python' started by mamboknave@gmail.com, Mar 2, 2013.

1. ### Guest

I cannot resolve this on my own. Need help, please...

nestedTuples = [
[ (L0t0e0, L0t0e1, L0t0e2), (L0t1e0, 2, L0t1e2), (L0t2e0, L0t2e1, L0t2e2) ],
[ (L1t0e0, L1t0e1, L1t0e2), (L1t1e0, 0, L1t1e2), (L1t2e0, L1t2e1, L1t2e2) ],
[ (L2t0e0, L2t0e1, L2t0e2), (L2t1e0, 1, L2t1e2), (L2t2e0, L2t2e1, L2t2e2) ] ]

With LNtXeY I mean the element Y in the tuple X of the list N.

How can I sort nestedTuples by, say, the 2nd element in the 2nd tuple of each list?

The above should get sorted as :

nestedTuples = [
[ (L1t0e0, L1t0e1, L1t0e2), (L1t1e0, 0, L1t1e2), (L1t2e0, L1t2e1, L1t2e2) ],
[ (L2t0e0, L2t0e1, L2t0e2), (L2t1e0, 1, L2t1e2), (L2t2e0, L2t2e1, L2t2e2) ],
[ (L0t0e0, L0t0e1, L0t0e2), (L0t1e0, 2, L0t1e2), (L0t2e0, L0t2e1, L0t2e2) ] ]

Thanks so much!!

, Mar 2, 2013

2. ### Peter OttenGuest

wrote:

> I cannot resolve this on my own. Need help, please...
>
> nestedTuples = [
> [ (L0t0e0, L0t0e1, L0t0e2), (L0t1e0, 2, L0t1e2), (L0t2e0, L0t2e1, L0t2e2)
> [ ], (L1t0e0, L1t0e1, L1t0e2), (L1t1e0, 0, L1t1e2), (L1t2e0, L1t2e1,
> [ L1t2e2) ], (L2t0e0, L2t0e1, L2t0e2), (L2t1e0, 1, L2t1e2), (L2t2e0,
> [ L2t2e1, L2t2e2) ] ]
>
> With LNtXeY I mean the element Y in the tuple X of the list N.
>
> How can I sort nestedTuples by, say, the 2nd element in the 2nd tuple of
> each list?

def getkey(item):
return item[1][1]
namedTuples.sort(key=getkey)

You can also write this as

namedTuples.sort(key=lambda item: item[1][1])

> The above should get sorted as :
>
> nestedTuples = [
> [ (L1t0e0, L1t0e1, L1t0e2), (L1t1e0, 0, L1t1e2), (L1t2e0, L1t2e1, L1t2e2)
> [ ], (L2t0e0, L2t0e1, L2t0e2), (L2t1e0, 1, L2t1e2), (L2t2e0, L2t2e1,
> [ L2t2e2) ], (L0t0e0, L0t0e1, L0t0e2), (L0t1e0, 2, L0t1e2), (L0t2e0,
> [ L0t2e1, L0t2e2) ] ]

Peter Otten, Mar 2, 2013

3. ### Guest

On Saturday, March 2, 2013 9:36:43 AM UTC-8, Peter Otten wrote:
>
> You can also write this as
>
> namedTuples.sort(key=lambda item: item[1][1])
>

That's exactly what I did before and got "IndexError: list index out of range".

So, I thought my lambda was wrong and posted here.

Now, having seen you reply, I dug deeper and... of course I had IndexError: the list was horribly empty!

Thanks so much for replying so quickly, Peter!

, Mar 2, 2013
4. ### Guest

On Saturday, March 2, 2013 9:36:43 AM UTC-8, Peter Otten wrote:
>
> You can also write this as
>
> namedTuples.sort(key=lambda item: item[1][1])
>

That's exactly what I did before and got "IndexError: list index out of range".

So, I thought my lambda was wrong and posted here.

Now, having seen you reply, I dug deeper and... of course I had IndexError: the list was horribly empty!

Thanks so much for replying so quickly, Peter!

, Mar 2, 2013