Misuse of list comprehensions?

[Ian Kelly]

On Tue, May 20, 2008 at 11:19 AM, John Salerno <johnjsal at nospamgmail.com> wrote:
> "Diez B. Roggisch" <deets at nospam.web.de> wrote in message
> news:69g605F2v4102U2 at mid.uni-berlin.de...
>> After being corrected about missing the construction of a None-containing
>> list, one needs of course to think about the waste of resources, as a
>> possible result-list is created in any case.
>
> Yeah, I was already aware of the list of Nones, which is why I asked. Simply
> typing the list comprehension without an assignment just *looked* wrong,
> too.

It sounds like the wasteful list creation is the biggest objection to
using a list comprehension.  I'm curious what people think of this
alternative, which avoids populating the list by using a generator
expression instead (apart from the fact that this is still quadratic,
which I'm aware of).

def compress(s):
   new = []
   filter(None, (new.append(c) for c in s if c not in new))
   return ''.join(new)