All permutations from 2 lists

[Antoon Pardon]

Op 2/03/2022 om 15:58 schreef Larry Martell:
> On Wed, Mar 2, 2022 at 9:37 AM Antoon Pardon<antoon.pardon at vub.be>  wrote:
>>
>>>>> If one list is empty I want just the other list. What I am doing is
>>>>> building a list to pass to a mongodb query. If region is empty then I
>>>>> want to query for just the items in the os list. I guess I can test
>>>>> for the lists being empty, but I'd like a solution that handles that
>>>>> as down the road there could be more than just 2 lists.
>>>> How about the following: Keep a list of your lists you want to permute over.
>>>> Like the following:
>>>>
>>>> permutation_elements = [["Linux","Windows"],["us-east-1", "us-east-2"]]
>>>>
>>>> permutation = itertools.product(*permutation_elements)
>>>>
>>>> If you don't include the empty list, you will get more or less what you
>>>> seem to want.
>>> But I need to deal with that case.
>> What does that mean? How does using the above method to produce the permutations
>> you want, prevent you from dealing with an empty list however you want when you
>> encounter them? Just don't add them to the permutation_elements.
> I need to know what items are in which position. If sometimes the
> regions are in one index and sometimes in another will not work for
> me.

I am starting to suspect you didn't think this through. What you are telling here
contradicts what you told earlier that if either list was empty, you just wanted
the other list. Because then you wouldn't know what items were in that list.

The only solution I can see now is that if a list is empty, you either add [None] or
[""] to the permutation_elements (whatever suits you better) and then use
itertools.product