Generate Cartesian Products with Itertools Incrementally

[CoderMan]

Hello,

I know I can get Cartesian products using

itertools.product(a,b)

Assuming that

a = ['a','b']

and

b = ['1','2']

the result would be (a1,a2,b1,b2).

How can I get the result (a,b,a1,a2,b1,b2)? That is, how can I get the shortest possible products first and then increment to the longest ones?

Thanks