#Input
A = [1,2,0]
#Output
B = [[0,0,0],
     [1,0,0],
     [1,1,0],
     [1,2,0],
     [0,1,0],
     [0,2,0]]

>>> from itertools import product
>>> A
[1, 2, 0]
>>> list(product(*[list(range(e+1)) for e in A]))
[(0, 0, 0), (0, 1, 0), (0, 2, 0), (1, 0, 0), (1, 1, 0), (1, 2, 0)]
>>>