Extracting an undefined number of items from a list

[Patrick Maupin]

On Apr 12, 3:05 pm, vsoler <vicente.so... at gmail.com> wrote:
> 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?

With a list comprehension:

>>> db=[10,20,30,40,50,60,70,80,90]
>>> i=[3,5,7]
>>> [db[x-1] for x in i]
[30, 50, 70]

Regards,
Pat