[Tutor] List comprehension question

[Wayne Werner]

On Sun, Nov 7, 2010 at 7:15 PM, Richard D. Moores <rdmoores at gmail.com>wrote:

> On Sun, Nov 7, 2010 at 16:41, Wayne Werner <waynejwerner at gmail.com> wrote:
> > On Sun, Nov 7, 2010 at 6:31 PM, Hugo Arts <hugo.yoshi at gmail.com> wrote:
> <snip>
> I should have mentioned that I'm using 3.1 .
>
> So this version of my function uses a generator, range(), no?
>

Correct. The rule of thumb for this type of thing is that if you care about
the entire object/collection, you should use a listcomp (or range in 2.x),
but if you only care about individual elements you should always use a
generator. Your function is a perfect example of this - you only care about
the individual #s from 1 up to n, not the collection of numbers as a whole,
so a generator is what you should prefer.


>
> def proper_divisors(n):
>    sum_ = 0
>    for x in range(1,n):
>        if n % x == 0:
>            sum_ += x
>    return sum_
>

Generators are super powerful, and my preferred reference on the subject is
here: www.dabeaz.com/*generators*/

-Wayne
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