查找N组中N个项目的所有组合，而不重复项目组合（python）？

Question

I'm trying to figure out a way of calculating all possible combinations of features of a certain product and have them returned as a list, without duplicates.

I have the items (features of the product) grouped in this kind of manner:

a
   a1
   a2
   a3

b
   b1
   b2

c
   c1
   c2
   c3
   c4

The number of groups and items are unknown, so there are in fact N groups and N items.

Example combinations:

# Combinations with 3 groups
a1_b1_c1
a1_b2_c1
a1_b3_c1
...and so on

# Combinations with 4 groups
a1_b1_c1_d1
a1_b2_c1_d1
a1_b3_c1_d1
...and so on

I would consider a1_b2_c3 and a1_c3_b2 to be duplicates, and I would not want any duplicates in the returned list.

A product without all features, such as a1_b2 or b2 would not be a valid product and thus I do not want those in the returned list either.

I've looked into itertools but I'm stuck. Any ideas?

Answer 1

You definitely want itertools.product:

import itertools

for i in itertools.product(['a1','a2','a3'], ['b1','b2'],['c1','c2','c3','c4']):
    print '_'.join(i)

RETURNS

a1_b1_c1
a1_b1_c2
a1_b1_c3
...
a3_b2_c1
a3_b2_c2
a3_b2_c3
a3_b2_c4