Permutation of two lists

Question

I have two lists:

first = ["one", "two", "three"]
second = ["five", "six", "seven"]

I want every single combination of those two lists but with elements from the first list always to be in front. I tried something like this:

for i in range(0, len(combined) + 1):
    for subset in itertools.permutations(combined, i):
        print('/'.join(subset))

Where "combined" was these two list combined but that gave me all of the possibilities and i just want those where elements from the first list are in the first place. For example:

["onefive","twosix","twofive"]

etc. Does anyone have an Idea how could I make this?

In this example, do you want all 9 combinations? – Tom Karzes Oct 01 '17 at 23:10 — Tom Karzes, Oct 01 '17 at 23:10
Yes, I do want all 9 combinations. – WholesomeGhost Oct 01 '17 at 23:10 — WholesomeGhost, Oct 01 '17 at 23:10

score 2 · Accepted Answer · answered Oct 01 '17 at 23:11

2

This should do what you're looking for:

>>> ["/".join(x) for x in itertools.product(first, second)]
['one/five', 'one/six', 'one/seven', 'two/five', 'two/six', 'two/seven', 'three/five', 'three/six', 'three/seven']
>>>

You can also do it without itertools:

>>> [x + "/" + y for x in first for y in second]
['one/five', 'one/six', 'one/seven', 'two/five', 'two/six', 'two/seven', 'three/five', 'three/six', 'three/seven']
>>>

answered Oct 01 '17 at 23:11

Tom Karzes

22,815
2
22
41

The OP wants the cartesian product. Using `itertools.product` is the right thing to do. – mkrieger1 Oct 01 '17 at 23:22

score 2 · Answer 2 · answered Oct 01 '17 at 23:13

2

Sometimes using normal loops is the easiest:

["{}/{}".format(j,k) for j in first for k in second]

>>> ['one/five', 'one/six', 'one/seven', 'two/five', 'two/six', 
     'two/seven', 'three/five', 'three/six', 'three/seven']

answered Oct 01 '17 at 23:13

ImportanceOfBeingErnest

321,279
53
665
712

I agree, they certainly are better. Upvoted. – cs95 Oct 01 '17 at 23:15

Permutation of two lists

2 Answers2