distance_permutation.py

def distance_permutation(array, d):
  """
  This function returns a staggered permutation of a sequence an the corresponding
  permuted indices, such that no item is allowed to move more than d steps from
  it's original position.
  """
    rng = range(len(array))
    for i in rng:
        swap = randint(0, d)
        if i - swap < rng[i] < i + swap:
            rng[i], rng[min(len(array)-1, i+swap)] = rng[min(len(array)-1, i+swap)], rng[i]
    return array[rng], rng