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Re: Extracting subsequences composed of the same character

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In article <4d952008$0$3943$426a74cc@news.free.fr>,
 candide <candide@free.invalid> wrote:

> Suppose you have a string, for instance
> 
> "pyyythhooonnn ---> ++++"
> 
> and you search for the subquences composed of the same character, here 
> you get :
> 
> 'yyy', 'hh', 'ooo', 'nnn', '---', '++++'

I got the following. It's O(n) (with the minor exception that the string 
addition isn't, but that's trivial to fix, and in practice, the bunches 
are short enough it hardly matters).

#!/usr/bin/env python                                                                               

s = "pyyythhooonnn ---> ++++"
answer = ['yyy', 'hh', 'ooo', 'nnn', '---', '++++']

last = None
bunches = []
bunch = ''
for c in s:
    if c == last:
        bunch += c
    else:
        if bunch:
            bunches.append(bunch)
        bunch = c
        last = c
bunches.append(bunch)

multiples = [bunch for bunch in bunches if len(bunch) > 1]
print multiples
assert(multiples == answer)


[eagerly awaiting a PEP for collections.bunch and 
collections.frozenbunch]

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Thread

Extracting subsequences composed of the same character candide <candide@free.invalid> - 2011-04-01 02:43 +0200
  Re: Extracting subsequences composed of the same character MRAB <python@mrabarnett.plus.com> - 2011-04-01 02:16 +0100
  Re: Extracting subsequences composed of the same character Roy Smith <roy@panix.com> - 2011-03-31 21:40 -0400
  Re: Extracting subsequences composed of the same character Tim Chase <python.list@tim.thechases.com> - 2011-03-31 20:58 -0500
  Re: Extracting subsequences composed of the same character Tim Chase <python.list@tim.thechases.com> - 2011-03-31 21:20 -0500
  Re: Extracting subsequences composed of the same character Terry Reedy <tjreedy@udel.edu> - 2011-04-01 00:18 -0400
  Re: Extracting subsequences composed of the same character candide <candide@free.invalid> - 2011-04-01 21:39 +0200

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