new_contents: """
  This is a Python implementation of the levenshtein distance.
  Levenshtein distance is a string metric for measuring the
  difference between two sequences.
  
  For doctests run following command:
  python -m doctest -v levenshtein-distance.py
  or
  python3 -m doctest -v levenshtein-distance.py
  
  For manual testing run:
  python levenshtein-distance.py
  """
  
  
  def levenshtein_distance(first_word, second_word):
      """Implementation of the levenshtein distance in Python.
      :param first_word: the first word to measure the difference.
      :param second_word: the second word to measure the difference.
      :return: the levenshtein distance between the two words.
      Examples:
      >>> levenshtein_distance("planet", "planetary")
      3
      >>> levenshtein_distance("", "test")
      4
      >>> levenshtein_distance("book", "back")
      2
      >>> levenshtein_distance("book", "book")
      0
      >>> levenshtein_distance("test", "")
      4
      >>> levenshtein_distance("", "")
      0
      >>> levenshtein_distance("orchestration", "container")
      10
      """
      # The longer word should come first
      if len(first_word) < len(second_word):
          return levenshtein_distance(second_word, first_word)
  
      if len(second_word) == 0:
          return len(first_word)
  
      previous_row = range(len(second_word) + 1)
  
      for i, c1 in enumerate(first_word):
  
          current_row = [i + 1]
  
          for j, c2 in enumerate(second_word):
  
              # Calculate insertions, deletions and substitutions
              insertions = previous_row[j + 1] + 1
              deletions = current_row[j] + 1
              substitutions = previous_row[j] + (c1 != c2)
  
              # Get the minimum to append to the current row
              current_row.append(min(insertions, deletions, substitutions))
  
          # Store the previous row
          previous_row = current_row
  
      # Returns the last element (distance)
      return previous_row[-1]
  
  
  if __name__ == '__main__':
      try:
          raw_input          # Python 2
      except NameError:
          raw_input = input  # Python 3
  
      first_word = raw_input('Enter the first word:\n').strip()
      second_word = raw_input('Enter the second word:\n').strip()
  
      result = levenshtein_distance(first_word, second_word)
      print('Levenshtein distance between {} and {} is {}'.format(
          first_word, second_word, result))
  
subject: add levenshtein distance metric