remove list elements..

[Carsten Haese]

On Fri, 2007-10-05 at 07:27 -0700, Abandoned wrote:
> Hi..
> I have a problem..
> list1=[11, 223, 334, 4223...] 1 million element
> list2=[22,223,4223,2355...] 500.000 element
> 
> I want to difference list1 to list2 but order very importent..
> 
> My result must be:
> list3=[11,334,...]
> 
> I do this use FOR easly but the speed very imported for me. I want to
> the fastest method please help me.

If you can write this as a for/append loop, then you can easily rewrite
it into a list comprehension:

<blank1> = []
for <blank2> in <blank3>:
  if <blank4>:
     <blank1>.append(<blank2>)

becomes

<blank1> = [<blank2> for <blank2> in <blank3> if <blank4>]

Now all you need to do is fill in the blanks.

As a hint for what exactly to fill in for blank4, remember (or be
advised) that Python has sets.

HTH,

-- 
Carsten Haese
http://informixdb.sourceforge.net