title: how can i compute the Levenshtein distance between sentences in a text
body: <p>I want to compute the Levenshtein distance between the sentences in one document. and I found a code that compute the distance in character level, but i want it to be in word-level.
   for instance, the output of this character level is 6， but i want it to be 1, which means only one word need to be deleted if we wanna change b to a or a to b ：</p>
  
  <pre><code>a = "The patient tolerated this ."
  b = "The patient tolerated ."
  
  def levenshtein_distance(a, b):
  
      if a == b:
          return 0
      if len(a) &lt; len(b):
          a, b = b, a
      if not a:
          return len(b)
      previous_row = range(len(b) + 1)
      for i, column1 in enumerate(a):
          current_row = [i + 1]
          for j, column2 in enumerate(b):
              insertions = previous_row[j + 1] + 1
              deletions = current_row[j] + 1
              substitutions = previous_row[j] + (column1 != column2)
              current_row.append(min(insertions, deletions,    substitutions))
              previous_row = current_row
      print (previous_row[-1]) 
      return previous_row[-1] 
  
  result = levenshtein_distance(a, b)
  </code></pre>