[Tutor] Combination

[Guillermo Fernandez Castellanos]

Hi,

I'm trying to take a list and find all the unique combinations of that list.

I mean:
if I enter (1,2,3,4,5) and I watn combinations of 3, I want to find:
(1,2,3) but then not (2,1,3), (3,1,2),...
(1,2,4)
(1,2,5)
(2,3,5)
(3,4,5)

The thing is, I want to do it as a generic function, where I pass a
list, and the length of the combination I want,

For the pervious example, it would be:
createComb([1,2,3,4,5],3)

I have no idea how to do it in a generic way.
For a given list and a length of 4 I did this:
def createComb(positions):
    """Returns all possible combinations of position of nbUnit units"""
    uniq={}
    result=[]
    for p1 in positions:
        for p2 in positions:
            for p3 in positions:
                for p4 in positions:
                    uniq[p1]=0
                    uniq[p2]=0
                    uniq[p3]=0
                    uniq[p4]=0
                    if len(uniq)==4:
                        result.append([p1,p2,p3,p4])
                    uniq={}
    return result

but is not very elegant...

Any suggestion?

Thanks,

G