Finding permuations and combinations using Python

Question

I have 2 variables - a and b. I need to fill up k places using these variables. So if k = 3 output should be

[a,a,a], [a,a,b] , [a,b,a], [b,a,a], [a,b,b], [b,a,b], [b,b,a] and [b,b,b]

Input - k

Output - All the combinations

How do I code this in Python? Can itertools be of any help here?

SilentGhost · Accepted Answer · 2010-10-14 10:29:01Z

6

>>> import itertools
>>> list(itertools.product('ab', repeat=3))
[('a', 'a', 'a'), ('a', 'a', 'b'), ('a', 'b', 'a'), ('a', 'b', 'b'), ('b', 'a', 'a'), ('b', 'a', 'b'), ('b', 'b', 'a'), ('b', 'b', 'b')]

answered Oct 14, 2010 at 10:29

SilentGhost

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2 Comments

tsimbalar Over a year ago

That's what I call "batteries included" :-)

SilentGhost Over a year ago

@Glenn: you forgot convert each result to list.

Andy · Accepted Answer · 2010-10-14 10:53:27Z

1

def genPerm(varslist, pos,resultLen, result, resultsList)
   if pos>resultLen:
       return;
   for e in varslist:
       if pos==resultLen:
           resultsList.append(result + [e]);
       else
           genPerm(varsList, pos+1, resultLen, result + [e], resultsList);

Call with:

genPerm([a,b], 0, resLength, [], resultsList);

edited Oct 14, 2010 at 10:53

answered Oct 14, 2010 at 10:40

Andy

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