Re: Detecting repeated subsequences of identical items

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From	Chris Angelico <rosuav@gmail.com>
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Subject	Re: Detecting repeated subsequences of identical items
Date	Thu, 21 Apr 2016 15:37:38 +1000
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On Thu, Apr 21, 2016 at 1:07 PM, Steven D'Aprano <steve@pearwood.info> wrote:
> Now I want to group subsequences. For example, I have:
>
> "ABCABCABCDEABCDEFABCABCABCB"
>
> and I want to group it into repeating subsequences. I can see two ways to
> group it:
>
> ABC ABC ABCDE ABCDE F ABC ABC ABC B
>
> or:
>
> ABC ABC ABC D E A B C D E F ABC ABC ABC B

Interesting. I've *almost* managed to (ab)use re.split for this
purpose. A one-step solution can be done with re.match:

>>> txt = "ABCABCABCDEABCDEFABCABCABCB"
>>> re.match(r'(.+)\1+', txt)
<_sre.SRE_Match object; span=(0, 9), match='ABCABCABC'>

But split then returns only the grouped part:

>>> re.split(r'(.+)\1+', txt)
['', 'ABC', 'DEABCDEF', 'ABC', 'B']

or *all* the grouped parts:

>>> re.split(r'((.+)\2+)', txt)
['', 'ABCABCABC', 'ABC', 'DEABCDEF', 'ABCABCABC', 'ABC', 'B']

There's definitely a partial solution happening here, but I can't
quite make it work.

And no, I don't know if there's a standard name for it.

ChrisA

Thread

Detecting repeated subsequences of identical items Steven D'Aprano <steve@pearwood.info> - 2016-04-21 13:07 +1000
  Re: Detecting repeated subsequences of identical items Ethan Furman <ethan@stoneleaf.us> - 2016-04-20 20:57 -0700
  Re: Detecting repeated subsequences of identical items Ethan Furman <ethan@stoneleaf.us> - 2016-04-20 21:15 -0700
  Re: Detecting repeated subsequences of identical items Chris Angelico <rosuav@gmail.com> - 2016-04-21 15:37 +1000
  Re: Detecting repeated subsequences of identical items Michael Selik <michael.selik@gmail.com> - 2016-04-21 06:35 +0000
    Re: Detecting repeated subsequences of identical items Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-04-21 18:05 +1000
      Re: Detecting repeated subsequences of identical items Nobody <nobody@nowhere.invalid> - 2016-04-21 13:02 +0100
  Re: Detecting repeated subsequences of identical items Michael Selik <michael.selik@gmail.com> - 2016-04-21 06:49 +0000
  Re: Detecting repeated subsequences of identical items Vlastimil Brom <vlastimil.brom@gmail.com> - 2016-04-21 08:54 +0200
  Re: Detecting repeated subsequences of identical items Michael Selik <michael.selik@gmail.com> - 2016-04-21 07:05 +0000
  Re: Detecting repeated subsequences of identical items Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2016-04-21 09:25 +0200
  Re: Detecting repeated subsequences of identical items Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2016-04-21 09:53 +0100
    Re: Detecting repeated subsequences of identical items Steven D'Aprano <steve@pearwood.info> - 2016-04-21 22:15 +1000
      Re: Detecting repeated subsequences of identical items Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2016-04-21 15:01 +0100
      Re: Detecting repeated subsequences of identical items Chris Angelico <rosuav@gmail.com> - 2016-04-22 00:12 +1000
        Re: Detecting repeated subsequences of identical items Steven D'Aprano <steve@pearwood.info> - 2016-04-23 01:00 +1000
      Re: Detecting repeated subsequences of identical items Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2016-04-21 15:30 +0100
      Re: Detecting repeated subsequences of identical items Chris Angelico <rosuav@gmail.com> - 2016-04-22 01:02 +1000
  Re: Detecting repeated subsequences of identical items Serhiy Storchaka <storchaka@gmail.com> - 2016-04-21 14:56 +0300

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