Natural sort of a list of lists based on an alphanumeric string within sub-list?

Question

Clear as mud, aye? I'll start with an example...

my_list = [[4,'A4, A23, A3, A6', 'Description 1', 'Property 1'],
           [4,'B3, B35, B10, B22', 'Description 2', 'Property 2'],
           [6,'A1, A11, A10, A21, A2, A22', 'Description 3', 'Property 3']]

Should sort to:

>>>my_list:
[[6,'A1, A2, A10, A11, A21,  A22', 'Description 3', 'Property 3'] 
 [4,'A3, A4, A6, A23', 'Description 1', 'Property 1'],
 [4,'B3, B10, B22, B35', 'Description 2', 'Property 2']]

So, I first need to naturally sort the string in the second index of every sub-list, then I need to naturally sort all of the lists based on the string in the second index of sub-list. I have been banging my head against the wall on this all day, so me posting any code that I have tried would probably just lead this down the wrong track.

Perhaps my initial sample case wasn't robust enough, but this is the result I am getting based on @Ashwini's code:

[[ 1,   'C1', 'DW-00232'],
 [3,    'C11, C32, C46', 'DW-6546'],
 [7,    'C16, C17, C18, C19, C20, C21, C25', 'DW-545'],
 [5,    'C2, C3, C4, C5, C63', 'DW-7657'],
 [1,    'C26', 'DW-0056'],
 [2,    'C59, C60', 'DW-23424'],
 [5,    'C6, C13, C24, C30, C64', 'DW-5345']]

I would like the output to be as follows:

[[ 1,   'C1', 'DW-00232'],
 [5,    'C2, C3, C4, C5, C63', 'DW-7657'],
 [5,    'C6, C13, C24, C30, C64', 'DW-5345'],
 [3,    'C11, C32, C46', 'DW-6546'],
 [7,    'C16, C17, C18, C19, C20, C21, C25', 'DW-545'],
 [1,    'C26', 'DW-0056'],
 [2,    'C59, C60', 'DW-23424']]

The goal posts keep moving. Now I need to consider a case where some of the alpha-numeric combos are in parentheses. I need to ignore the parenthesis during the sort.

Example:

[[ 1, 'C1', 'DW-00232'],
 [ 7, '(C21), C16, (C7), (C18), C19, C6, C65', 'DW-545'],
 [ 5, ' C4, (C2), C3, C10, (C5)', 'DW-7657']]

Sorts to this:

[[ 1, 'C1', 'DW-00232'],
 [ 5, '(C2), C3, C4, (C5), C10', 'DW-7657'],    
 [ 7, 'C6, (C7), C16, (C18), C19, (C21), C65', 'DW-545']]

Okay, the above case was an 'easy' fix, once I inspected Ashwini's code a little closer. I added the translate statement to his natural sort function to the following, based on how he handled his key function (since that was sorting the way I wanted, it was only the per-line sort that wasn't right), as follows.

        alphanum_key = (lambda key:
                        [convert(c.translate(None, punctuation + whitespace)) for c in re.split('([0-9]+)', key)])

Yes. The first sort should sort the second index of each sub-list, then the second sort should sort each sub-list based on the second index of each sub-list. Is that not clear? (not trying to be condescending, I just don't know how clear I am being.) — realityinabox, Mar 07 '14 at 19:11
Ah, I see now. It's just unusual to want to sort pieces of a string, so I wasn't expecting it; normally it would contain an actual list, which would be sortable as expected. — Ignacio Vazquez-Abrams, Mar 07 '14 at 19:17

score 1 · Accepted Answer · edited May 23 '17 at 10:26

Using the natural_sort function from this answer you can do something like this:

import re
from string import punctuation as punc, whitespace as wt
from pprint import pprint

def natural_sort(l): 
    #https://stackoverflow.com/a/4836734/846892
    convert = lambda text: int(text) if text.isdigit() else text.lower() 
    alphanum_key = lambda key: [ convert(c) for c in re.split('([0-9]+)', key) ] 
    return sorted(l, key = alphanum_key)

def key(seq):                                           
    convert = lambda text: int(text) if text.isdigit() else text.lower() 
    return [convert(c.translate(None, punc+wt)) for c in re.split('([0-9]+)', seq)]
... 
>>> my_list = [[ 1,   'C1', 'DW-00232'],
 [3,    'C11, C32, C46', 'DW-6546'],
 [7,    'C16, C17, C18, C19, C20, C21, C25', 'DW-545'],
 [5,    'C2, C3, C4, C5, C63', 'DW-7657'],
 [1,    'C26', 'DW-0056'],
 [2,    'C59, C60', 'DW-23424'],
 [5,    'C6, C13, C24, C30, C64', 'DW-5345']]
>>> 
>>> new_lis = [x[:1] + [", ".join(natural_sort(x[1].split(', ')))] + x[2:]
                                                                for x in my_list]
>>> new_lis.sort(key = lambda x:key(x[1]))               
>>> pprint(new_lis)
[[1, 'C1', 'DW-00232'],
 [5, 'C2, C3, C4, C5, C63', 'DW-7657'],
 [5, 'C6, C13, C24, C30, C64', 'DW-5345'],
 [3, 'C11, C32, C46', 'DW-6546'],
 [7, 'C16, C17, C18, C19, C20, C21, C25', 'DW-545'],
 [1, 'C26', 'DW-0056'],
 [2, 'C59, C60', 'DW-23424']]
>>>

It appears that the first level of natural sort is working correctly, but the second level is not. Item Item Reference 1 1 A1 2 1 C1 3 3 C11, C32, C46 4 1 C14 5 1 C15 6 7 C16, C17, C18, C19, C20, C21, C25 7 5 C2, C3, C4, C5, C63` — realityinabox, Mar 07 '14 at 20:13
@realityinabox Post the data in question body not in comments. — Ashwini Chaudhary, Mar 07 '14 at 20:24
An alternative to hand-writing a natural_sort function is to use the `natsort` module. — SethMMorton, Jan 15 '15 at 03:58

score 0 · Answer 2 · answered Mar 07 '14 at 18:54

0

The default for sort is to use the builtin cmp to compare elements I think, but you can do, for example:

my_list.sort(key = lambda x: x[1])

That will instruct it to use the first element of every sublist as the comparison key

Edit: without lambdas...

from operator import itemgetter
my_list.sort(key = itemgetter(1))

answered Mar 07 '14 at 18:54

Ricardo Cárdenes

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This will only sort the lists. The OP needs to sort the lists _and_ sort the elements in the lists as well. – Drewness Mar 07 '14 at 18:57
And I need all these sorts to be 'natural'. (ie, A1, A2, A10, A20, not A1, A10, A2, A20) – realityinabox Mar 07 '14 at 18:59
Mmh.. For some reason I managed to overlook the sorting of the strings. – Ricardo Cárdenes Mar 07 '14 at 19:37

Natural sort of a list of lists based on an alphanumeric string within sub-list?

2 Answers2