An example of a biased shuffle

bad_shuffle.py

import random

def swap(array, i, j):
  array[i], array[j] = array[j], array[i]
  
def shuffle(array):
  n = len(array)
  swapped = [False]*n
  while not all(swapped):
    i, j = random.randrange(n), random.randrange(n)
    swap(array, i, j)
    swapped[i] = swapped[j] = True