All permutations from 2 lists

[Larry Martell]

On Wed, Mar 2, 2022 at 8:37 AM Antoon Pardon <antoon.pardon at vub.be> wrote:
>
>
> Op 2/03/2022 om 14:27 schreef Larry Martell:
> > On Tue, Mar 1, 2022 at 7:21 PM<2QdxY4RzWzUUiLuE at potatochowder.com>  wrote:
> >> On 2022-03-01 at 19:12:10 -0500,
> >> Larry Martell<larry.martell at gmail.com>  wrote:
> >>
> >>> If I have 2 lists, e.g.:
> >>>
> >>> os = ["Linux","Windows"]
> >>> region = ["us-east-1", "us-east-2"]
> >>>
> >>> How can I get a list of tuples with all possible permutations?
> >>>
> >>> So for this example I'd want:
> >>>
> >>> [("Linux", "us-east-1"), ("Linux", "us-east-2"), ("Windows",
> >>> "us-east-1"), "Windows", "us-east-2')]
> >>>
> >>> The lists can be different lengths or can be 0 length. Tried a few
> >>> different things with itertools but have not got just what I need.
> >> [(o, r) for o in os for r in region]
> > This does not work if region = []. I wrote in my question that either
> > list could be empty.
>
> What do you mean it doesn't work? The result seems to be an empty list,
> which IMO is a perfectly valid result.
>
> All possible permutations over two collections where one collection is
> empty, should IMO give you an empty collection.

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.