title: Python searching a large list speed
body: <p>I have run into a speed issue searching through a very large list. I have a file with a lot of errors and very strange words in it. I am trying to use difflib to find the closest match in a dictionary file I have that has 650,000 words in it. This approach below works really well but is very very slow and I was wondering if there is a better way to approach this problem. This is the code: </p>
  
  <pre><code>from difflib import SequenceMatcher
  headWordList = [ #This is a list of 650,000 words]
  
  
  openFile = open("sentences.txt","r")
  
  for line in openFile:
      sentenceList.append[line]
  
  percentage = 0
  count = 0
  
  for y in sentenceList:
        if y not in headwordList:
  
           for x in headwordList:
               m = SequenceMatcher(None, y.lower(), x)
  
               if m.ratio() &gt; percentage:
                   percentage = m.ratio()
  
                   word = x
  
           if percentage &gt; 0.86:        
               sentenceList[count] = word
  count=count+1
  </code></pre>
  
  <p>Thanks for the help, software engineering is not even close to my strong suit. Much appreciated.</p>