Extracting an undefined number of items from a list

[vsoler]

Hi everyone,

say that 'db' is a list of values
say 'i' is a list of indexes
I'd like to get a list where each item is i-th element of db.

For example:

db=[10,20,30,40,50,60,70,80,90]      #undefined length
i=[3,5,7]                                         #undefined length
then result=[30,50,70]                     # resulting list

how can I do this?