How to index an array with even steps?

[fl]

Hi,

I have an array arr which is indexed from 0 to 999. I would like to construct a 
column in two steps. The first step is input from 200 data, evenly spread from 0
to 999 of the target array. Then, I want to use interpolate it from 200 to 1000
with interpolate method.

In Python, ':' is used to indicate range (while in Matlab I know it can be used
to control steps). How to index an array with 0, 5, 10, 15...995?


Thanks,