input: def bubble_sort(arr):
      n = len(arr)
      for i in range(n-1):
          for j in range(0, n-i-1):
              if arr[j] > arr[j+1]:
                  arr[j], arr[j+1] = arr[j+1], arr[j]
  
  arr = [3,7,4,1]
  bubble_sort(arr)
  print ("Sorted array :")
  for i in range(len(arr)):
      print ("%d" %arr[i]),
  
  # Example:
  # for bubble_sort([3, 7, 4, 1]) == [1, 3, 4, 7]
output:     return arr