dict generator question

[Gerard flanagan]

Simon Mullis wrote:
> Hi,
> 
> Let's say I have an arbitrary list of minor software versions of an
> imaginary software product:
> 
> l = [ "1.1.1.1", "1.2.2.2", "1.2.2.3", "1.3.1.2", "1.3.4.5"]
> 
> I'd like to create a dict with major_version : count.
> 
> (So, in this case:
> 
> dict_of_counts = { "1.1" : "1",
>                    "1.2" : "2",
>                    "1.3" : "2" }
> 

[...]
data = [ "1.1.1.1", "1.2.2.2", "1.2.2.3", "1.3.1.2", "1.3.4.5"]

from itertools import groupby

datadict = \
   dict((k, len(list(g))) for k,g in groupby(data, lambda s: s[:3]))
print datadict