Count Sort Python Implementation

count_sort.py

def count_sort(array):
  
  # The output character array that will have sorted arr
  output = [0 for i in range(256)]

  # Create a count array to store count of inidividul 
  # characters and initialize count array as 0 
  count = [0 for i in range(256)]

  # For storing the resulting answer since the  
  # string is immutable 
  result = ["" for _ in array]

  # Store count of each character
  for i in array:
    count[ord(i)] += 1
  
  # Change count[i] so that count[i] now contains actual 
  # position of this character in output array 
  for i in range(250):
    count[i] += count[i-1]
  
  # Build the output character array 
  for i in range(len(array)):
    output[count[ord(array[i])]-1] = array[i]
    count[ord(array[i])] -= 1
  
  # Copy the output array to arr, so that arr now 
  # contains sorted characters 
  for i in range(len(array)):
    result[i] = output[i]
  
  return result

assert ['_', 'c', 'n', 'o', 'o', 'r', 's', 't', 't', 'u'] == count_sort('count_sort')