dict generator question

[Simon Mullis]

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" }

Something like:

dict_of_counts = dict([(v[0:3], "count") for v in l])

I can't seem to figure out how to get "count", as I cannot do x += 1
or x++ as x may or may not yet exist, and I haven't found a way to
create default values.

I'm most probably not thinking pythonically enough... (I know I could
do this pretty easily with a couple more lines, but I'd like to
understand if there's a way to use a dict generator for this).

Thanks in advance

SM


-- 
Simon Mullis