[Tutor] Permutations?

[Hee-Seng Kye]

def perm(k):
     # Compute the list of all permutations of k
     if len(k) <= 1:
         return [k]
     r = []
     for i in range(len(k)):
         s =  k[:i] + k[i+1:]
         p = perm(s)
         for x in p:
             r.append(k[i:i+1] + x)
     return r

Could someone tell me how I can modify the above function so that it 
produces a list of permutations of k that only begins on k[0]?

If k = [0,1,2,3], I want to modify perm(k) so that it only produces 
[[0,1,2,3], [0,1,3,2], [0,2,1,3], [0,2,3,1], [0,3,1,2], [0,3,2,1]].

I could produce the list of ALL permutations of k and then delete the 
ones which don't begin with k[0], but for a large list, this could 
really slow things down.  I was thinking of algorithm that computes 
only the ones I want.

I would appreciate anyone's suggestion.  Thanks.

Best,
Kye

p.s. By the way, does anyone have any idea if it would drive my 
computer (667 MHz and 512MB RAM) nuts to perm(range(12))?