iterblocks cookbook example

[Steve Howell]

--- Raymond Hettinger <python at rcn.com> wrote:
> ISTM, this is a common mailing list problem because
> it is fun
> to solve, not because people actually need it on a
> day-to-day basis.
>

It comes up in the real world for me once very couple
months or so.  It's usually when I need to manipulate
data, but I also use the technique to write quick and
dirty tools to analyze code.
 
> In that spirit, it would be fun to compare several
> different
> approaches to the same problem using re.finditer,
> itertools.groupby,
> or the tokenize module.  To get the ball rolling,
> here is one variant:
> 
> from itertools import groupby
> 
> def blocks(s, start, end):
>     def classify(c, ingroup=[0], delim={start:2,
> end:3}):
>         result = delim.get(c, ingroup[0])
>         ingroup[0] = result in (1, 2)
>         return result
>     return [tuple(g) for k, g in groupby(s,
> classify) if k == 1]
> 

Neat.  I like the way you persist ingroup[0] from call
to call.

 
> One observation is that groupby() is an enormously
> flexible tool.
> Given a well crafted key= function, it makes short
> work of almost
> any data partitioning problem.
> 

Definitely.



       
____________________________________________________________________________________
Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. 
http://answers.yahoo.com/dir/?link=list&sid=396545433