Combinations of lists
Steven D'Aprano
steve+comp.lang.python at pearwood.info
Wed Oct 3 11:42:47 EDT 2012
On Wed, 03 Oct 2012 16:26:43 +0200, Steen Lysgaard wrote:
> Hi,
>
> I am looking for a clever way to compute all combinations of two lists.
> Look at this example:
>
> h = ['A','A','B','B']
> m = ['a','b']
>
> the resulting combinations should be of the same length as h and each
> element in m can be used twice.
Why twice? What if you had these?
h = ['A', 'A', 'B', 'B', 'C', 'D', 'E', 'E']
m = ['a', 'b', 'c']
Would you still use each element in m twice? Or some other number?
> The sought after result using h and m from above is:
>
> [['aA', 'aA', 'bB', 'bB'],
> ['aA', 'aB', 'bA', 'bB'],
> ['aB', 'aB', 'bA', 'bA']]
>
> (the order of the results does not matter i.e. ['aA', 'aA', 'bB', 'bB']
> and ['aA', 'bB', 'aA', 'bB'] are considered the same)
>
> This is achieved by the code below, this however needs to go through all
> possible combinations (faculty of len(h)) and rule out duplicates as
> they occur and this is too much if for example len(h) is 16.
I don't understand this requirement. In the example above, you don't rule
out duplicates. Both 'aA' and 'bB' are duplicated. What duplicates are
you ruling out?
--
Steven
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