Weighted "random" selection from list of lists

[Jesse Noller]

Hello -

I'm probably missing something here, but I have a problem where I am
populating a list of lists like this:

list1 = [ 'a', 'b', 'c' ]
list2 = [ 'dog', 'cat', 'panda' ]
list3 = [ 'blue', 'red', 'green' ]

main_list = [ list1, list2, list3 ]

Once main_list is populated, I want to build a sequence from items
within the lists, "randomly" with a defined percentage of the sequence
coming for the various lists. For example, if I want a 6 item
sequence, I might want:

60% from list 1 (main_list[0])
30% from list 2 (main_list[1])
10% from list 3 (main_list[2])

I know how to pull a random sequence (using random()) from the lists,
but I'm not sure how to pick it with the desired percentages.

Any help is appreciated, thanks

-jesse