Pick items from list with probability based upon property of list member ?

[southof40]

On Jun 20, 10:55 pm, Rob Williscroft <r... at rtw.me.uk> wrote:
> southof40 wrote in news:da3cc892-b6dd-4b37-a6e6-
> b606ef967... at t26g2000prt.googlegroups.com in gmane.comp.python.general:
>
> > I have list of of N Vehicle objects - the only possible vehicles are
> > cars, bikes, trucks.
>
> > I want to select an object from the list with a probability of : cars
> > 0.7, bikes 0.3, trucks 0.1.
>
> Aside, all your probabilities add up to 1.1, they should add up to 1.
>
> > I've currently implemented this by creating another list in which each
> > car object from the original list appears 7 times, each bike 3 times
> > and each truck once. I then pick at random from that list.
>
> Aside, so 7 / 11 bikes, 3 / 11 cars and 1 / 11 trucks, are your
> actual probabilities.
>
> But to answer your question, you could create 3 list, and then
> pick the list you draw from based on a random number then pick
> the item from the list based on another random number:
>
> r = ( random() * 11 )
>
> if r  < 1:
>   picklist = truck_list
> elif r  < 4:
>   picklist = bike_list
> else:
>   picklist = car_list
>
> # now pick the final item from pick list.
>
> Rob.

thanks also - nice clean solution