Jay Parlar wrote:
> On Dec 8, 2005, at 5:29 PM, [EMAIL PROTECTED] wrote:
> >
> > Hello all,
> >
> > I'm a beginner with programming. Trying to teach myself with that
> > excellent rat book. Unfortunately I just can't seem to figure out a
> > simple problem that has come up at my work (biology lab):
> > let's say I have a list
> > ['A','C','D','E','F','G','H','I','K','L','M','N','P','Q','R','S','T','V
> > ','W','Y'] . I need to generate permutations of this list. I have
> > found plenty of code on the web to generate ALL possible permutations.
> > What I need are all possible 4-letter permutations. I cannot seem to
> > figure out how to modify Mike Davie's permutation generator
> > http://www.bigbold.com/snippets/posts/show/753 to acheive this. Any
> > help would be appreciated.
> >
>
The 'kSubsets' function here:
http://www.gflanagan.net/site/python/05/kSubsetGenerator.html
should give you the combinations, though how well it does so is another
matter. (Only tested roughly). Then:
>>>import string
>>>choice = string.letters[26:]
>>>combinations = list(kSubsets(choice,4))
>>>print combinations
To get the permutations(no repeats) you can just permute each
combination, for which the Permutation class here:
http://www.gflanagan.net/site/python/05/Johnson.html
might help. Eg.
>>> def kPerms( alist, k ):
... n = len(alist)
... for vector in nkRange(n,k):
... for perm in Permutation(vector):
... ret = []
... for i in perm:
... ret.append( alist[i-1] )
... yield ret
...
>>> x = list( kPerms(choice, 3) )
>>> print x
Gerard
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