Permutations of an array in Python

permutations.py

def swap(a, i, j):
    t = a[i]
    a[i] = a[j]
    a[j] = t

def permutations(a, i, n):
    if i == n:
        print a
    else:
       for j in range(i, n):
          swap(a, i, j)
          permutations(a, i + 1, n)
          swap(a, i, j)

a = [1, 2, 3]
permutations(a, 0, len(a))

# Output:

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

# pic: http://d2o58evtke57tz.cloudfront.net/wp-content/uploads/NewPermutation.gif