Sorting list of AB strings based on the whole string

Question

I have the following list:

lst = ['AAAAAABB', 'AAAAAABA', 'AAAAAAAB', 'AAAAABAA', 'AAAAABAB', 'AAAAABBA']

And I'm getting this:

lst = ['AAAAAAAB', 'AAAAAABA', 'AAAAAABB', 'AAAAABAA', 'AAAAABAB', 'AAAAABBA']

But I want something like this:

lst = ['AAAAAAAB', 'AAAAAABA', 'AAAAABAA', 'AAAAAABB', 'AAAAABAB', 'AAAAABBA']

It means, I want to sort my list by Python considering the sequences of A and B in each list item.

Actually, I want that all the combinations with 7*A should appear first. After that should come the combinations with more than one B.

Possible duplicate of [How to sort a list of strings?](https://stackoverflow.com/questions/36139/how-to-sort-a-list-of-strings) — sco1, Oct 19 '17 at 17:00
The only difference in the order of the sorted list and your desired order is items at index 2 and 3 are swapped. For 'AAAAABAA', 'AAAAAABB', how do you determine the 'BAA' in the first sequence should appear before 'ABB', when lexicographically shouldn't 'A' appear *before* 'B'? — chickity china chinese chicken, Oct 19 '17 at 17:38
Actually, I want that all the combinations with 7*A should apears first. After that come the combinations with more than one B. — D. CompsNoob-G, Oct 19 '17 at 17:50
@Miraj50 what is the criteria of the order? why "AAAAABAA" < "AAAAAABB"? — developer_hatch, Oct 19 '17 at 18:10
@DamianLattenero I think because `AAAAABAA` has one `B` while the latter has two. — Miraj50, Oct 19 '17 at 18:12
mmm it's not enough info... we should wait for @DiegoGuedes-Sobrinho to clarify — developer_hatch, Oct 19 '17 at 18:13
Yes, @DamianLattenero is right! The criteria is the number of B's — D. CompsNoob-G, Oct 19 '17 at 18:22

developer_hatch · Accepted Answer · 2017-10-20T14:15:21.277

2

Edit: I always forget this comment, but it is really important, DO NOT CALL A VARIABLE WITH NAMES AS "list, dict" etc, those name has special meaning for python

Edit: you are sorting by amount of "b"

You can sort the list:

import functools

lst = ['AAAAAABB', 'AAAAAABA', 'AAAAAAAB', 'AAAAABAA', 'AAAAABAB', 'AAAAABBA']

def sort_by_b(a,b):
  ab = a.count('B')
  bb =  b.count('B')
  if (ab == bb and a < b) or ab < bb:
    return -1
  elif ab > bb:
    return 1
  else:
    return a == b

print(sorted(lst, key=functools.cmp_to_key(sort_by_b)))

as result:

['AAAAAAAB', 'AAAAAABA', 'AAAAABAA', 'AAAAAABB', 'AAAAABAB', 'AAAAABBA']

edited Oct 20 '17 at 14:15

answered Oct 19 '17 at 16:59

developer_hatch

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@Miraj50 what is the criteria of the order? – developer_hatch Oct 19 '17 at 18:09
Isn't the answer supposed to be `lst = ['AAAAAAAB', 'AAAAAABA', 'AAAAABAA', 'AAAAAABB', 'AAAAABAB', 'AAAAABBA']` – Miraj50 Oct 20 '17 at 05:01
@Miraj50 you were totally right, thank you so much, I corrected the answer. Please considere to read it – developer_hatch Oct 20 '17 at 14:15

Miraj50 · Answer 2 · 2017-10-19T18:44:41.200

2

I think I get what you are trying to do! Correct me if I am wrong. Basically it depends on B, isn't it? The more number of times B appears or closer is a B to the starting of a string, further away it appears in the final answer list, isn't it?

So, here is what I do.

First, I get a list in which the strings has been sorted in the order of the frequency of B.
This is not sufficient, as the order of the strings matter in the original list. For seeing this remove the for loop from my answer and print lst, you will clearly see the issue.

So now I need to sort(the normal lexicographic sort) each group of strings which have the same frequency of B. I used groupby for this. See the uses of groupby and sorted each such group and appended them to the final answer.

from itertools import groupby

lst = ['AAAAAABB', 'AAAAAABA', 'AAAAAAAB', 'AAAAABAA', 'AAAAABAB', 'AAAAABBA']
ans = []
lst.sort(key=lambda x:x.count('B'))
for i,j in groupby(lst, lambda x:x.count('B')):
    ans.extend(sorted(list(j)))

print ans

Output:

['AAAAAAAB', 'AAAAAABA', 'AAAAABAA', 'AAAAAABB', 'AAAAABAB', 'AAAAABBA']

edited Oct 19 '17 at 18:44

answered Oct 19 '17 at 17:00

Miraj50

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ahahahah we are in the same page, yes, totally right the answer. plus one – developer_hatch Oct 19 '17 at 17:03
Thank you guys. However, I have edited the post to make more clear. Please, if you could check it now. – D. CompsNoob-G Oct 19 '17 at 17:20
@DiegoGuedes-Sobrinho Good! Try figuring out how this works. Otherwise ask me and I shall explain it to you. Good Question, btw!! – Miraj50 Oct 19 '17 at 18:33
@Miraj50 damn, I don't know how did you achieve this, could you explain to me? – developer_hatch Oct 19 '17 at 18:36
@DiegoGuedes-Sobrinho Done. – Miraj50 Oct 19 '17 at 18:45

Sorting list of AB strings based on the whole string

2 Answers2