a_list.count(a_callable) ?

Ping ping.nsr.yeh at gmail.com
Fri Jun 15 19:52:55 CEST 2007


On 6 15 ,   11 17 , Dustan <DustanGro... at gmail.com> wrote:
> On Jun 15, 9:15 am, Ping <ping.nsr.... at gmail.com> wrote:
>
> > > sum(1 for i in a_list if a_callable(i))
>
> > > --
> > > Carsten Haesehttp://informixdb.sourceforge.net
>
> > This works nicely but not very intuitive or readable to me.
>
> > First of all, the generator expression makes sense only to
> > trained eyes.  Secondly, using sum(1 ...) to mean count()
> > isn't very intuitive either.
>
> Then wrap it in a function:
> def count(a_list, a_function):
>    return sum(1 for i in a_list if a_function(i))
>
> And call the function. You can also give it a different name (although
> I can't think of a concise name that would express it any better).
>

Hmm... This sounds like the best idea so far.  It is efficient both
in memory and time while exposes an easy-to-understand name.
I would name the function count_items though.

n = count_items(a_list, lambda x: x > 3)     # very readable  :)

cheers,
Ping




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