how to append to a list twice?

[Sion Arrowsmith]

John Salerno  <johnjsal at NOSPAMgmail.com> wrote:
>If I want to create a list of the form [100, 99, 99, 98, 98, 97, 97...] 
>(where each item is repeated twice after the first one), how might I do 
>that most efficiently?
>
>Right now I have this:
>
>series = [100]
>for x in range(10):   # just for testing
>     series.append(series[-1] - 1)
>
>But of course that only does it once, [ ... ]

You could try:

series = [100]
l = range(series[-1]-1, series[-1]-11, -1) #just for testing
s.extend(sum(zip(l, l), ()))

Times as faster than the series.extend([series[-1] - 1] * 2)
for me.

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