Modifying every alternate element of a sequence

[jm.suresh@no.spam.gmail.com]

I have a list of numbers and I want to build another list with every
second element multiplied by -1.

input = [1,2,3,4,5,6]
wanted = [1,-2,3,-4,5,-6]

I can implement it like this:

input = range(3,12)
wanted = []
for (i,v) in enumerate(input):
    if i%2 == 0:
        wanted.append(v)
    else:
        wanted.append(-v)

But is there any other better way to do this.

--
Suresh