Misuse of list comprehensions?

[Arnaud Delobelle]

"Ian Kelly" <ian.g.kelly at gmail.com> writes:

> 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)

This is crazy!

-- 
Arnaud