In case you can’t use Python’s itertools or in case you want a simple, recursive python implementation for a permutation of a list:

[python]

def perm(a,k=0):

if(k==len(a)):

print a

else:

for i in xrange(k,len(a)):

a[k],a[i] = a[i],a[k]

perm(a, k+1)

a[k],a[i] = a[i],a[k]

perm([1,2,3])

[/python]

Output:

[1, 2, 3] [1, 3, 2] [2, 1, 3] [2, 3, 1] [3, 2, 1] [3, 1, 2]

This Python implementation is based in the algorithm presented in the book Computer Algorithms by Horowitz, Sahni and Rajasekaran.

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