what improved doing combinations lexicographic method pointed list?

i put position now i indispensable enumerate illusory combinations pointed list. instance, genuine proceed be:

for [1,2,3]:
    b [4,5,6,7,8,9]:
        c [1,2]:
            furnish (a,b,c)

this functional, nonetheless whole terms array lists used. here some-more concept approach:

from numpy import zeros, array, nonzero, max

make_subset = lambda x,y: [x[i][j] i,j enumerate(y)]

def combinations(items):
    num_items = [len(i) - 1 i items]
    state = zeros(len(items), dtype=int)
    finished = array(num_items, dtype=int)
    furnish grab_items(items, state)
    while true:
        state[-1] != num_items[-1]:
            state[-1] += 1
            furnish make_subset(items, state)
        else:
            incrementable = nonzero(state != finished)[0]
            len(incrementable):
                lift stopiteration
            rightmost = max(incrementable)
            state[rightmost] += 1
            state[rightmost+1:] = 0
            furnish make_subset(items, state)

any recommendations improved proceed reasons opposing above approach?