counting items

[Paul McGuire]

"It's me" <itsme at yahoo.com> wrote in message
news:ukdFd.10645$5R.2000 at newssvr21.news.prodigy.com...
> Okay, I give up.
>
> What's the best way to count number of items in a list?
>
> For instance,
>
> a=[[1,2,4],4,5,[2,3]]
>
> I want to know how many items are there in a (answer should be 7 - I don't
> want it to be 4)
>
<snip>

I've sure seen a lot of questions about the flattening of lists.  I found
this version of flatten somewhere, I thought I got it from the Python
Cookbook but I can't find it now.  Perhaps it was posted here on c.l.py.  I
*don't* claim authorship, I'm merely an admirer of such a clean-looking
solution.

def flatten(a):
    if not isinstance(a, (tuple,list)): return [a]
    if len(a)==0: return []
    return flatten(a[0])+flatten(a[1:])

a = [[1, 2, 4], 4, 5, [2, 3], 6, [6], [], 'askjdf']

print len(flatten(a))

gives the value 10.

Considering how often this comes up, might there be a place for some sort of
flatten() routine in the std dist, perhaps itertools?

-- Paul