[Tutor] Combination

[Kent Johnson]

This question comes up regularly on comp.lang.python. Search the archives for 'combinations' to find 
*many* discussions of how to do it. Also there are several recipes in the cookbook.
http://groups-beta.google.com/group/comp.lang.python?hl=en&lr=&ie=UTF-8&c2coff=1
http://aspn.activestate.com/ASPN/Cookbook/Python

Kent

Guillermo Fernandez Castellanos wrote:
> 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
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