Misuse of list comprehensions?

[Ian Kelly]

On Tue, May 27, 2008 at 8:08 PM, Gabriel Genellina
<gagsl-py2 at yahoo.com.ar> wrote:
> En Tue, 27 May 2008 14:43:52 -0300, Ian Kelly <ian.g.kelly at gmail.com>
> escribió:
>
>> 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)
>
> filter returns a newly created list, so this code is as wasteful as a list
> comprehension (and harder to read).

Here it returns a newly created *empty* list, which is not nearly as
wasteful as one that's linear in the size of the input.  I'll grant
you the second point, though.  I very much doubt that I would ever
actually use this myself.  I was just curious what others would think
of it.