[Python] groupbyを使って文章中の文字をカウントする

ユニークイテレータなる groupby という関数を使ってみる。

例えば、今日のニュース記事の一段落で登場する文字をカウントしてみる。

The O+ Festival in San Francisco this weekend would seem a typical indie arts event, with performances by local musicians and displays of funky art. But in a twist that highlights a longstanding problem in the creative economy, the artists involved will be paid not in cash but rather in something they may need just as badly: health care.

出典 : Will Play for Health Care (at Least at One Music Event) - NYTimes.com

>>> article = """The O+ Festival in San Francisco this weekend would seem a typical indie arts event, with performances by local musicians and displays of funky art. But in a twist that highlights a longstanding problem in the creative economy, the artists involved will be paid not in cash but rather in something they may need just as badly: health care."""
>>> from itertools import groupby
>>> article_group = ((len(list(group)),character) 
...                  for character,group in groupby(sorted(article.lower())))
>>> for count, character in article_group:
...     print "%02d,%s"%(count, character)
... 
58, 
01,+
02,,
02,.
01,:
26,a
06,b
10,c
10,d
27,e
05,f
05,g
15,h
25,i
01,j
02,k
14,l
07,m
22,n
13,o
05,p
11,r
20,s
27,t
06,u
05,v
05,w
08,y

という感じで、最も多いのは半角スペースで58個、ついでe,tが27個ですね。
groupbyは連続している同じ要素をグループ化するので、
sorted関数で文字列を予め並べ替えておく必要があります。
また、今回は大文字小文字を区別しなかったので、lower関数を使っています。