title: TypeError: str object is not an iterator
body: <p>I have a file consisting of words, one word on each line. The file looks like this:</p>
  
  <pre><code>aaa
  bob
  fff
  err
  ddd
  fff
  err
  </code></pre>
  
  <p>I want to count the frequency of the pair of words which occur one after the other.</p>
  
  <p>For example,</p>
  
  <pre><code>aaa,bob: 1
  bob,fff:1
  fff,err:2
  </code></pre>
  
  <p>and so on.
   I have tried this</p>
  
  <pre><code>f=open(file,'r')
  content=f.readlines()
  f.close()
  dic={}
  it=iter(content)
  for line in content:
      print line, next(line);
      dic.update({[line,next(line)]: 1})
  </code></pre>
  
  <p>I got the error: </p>
  
  <pre><code>TypeError: str object is not an iterator
  </code></pre>
  
  <p>I then tried using an iterator:</p>
  
  <pre><code>it=iter(content)
  for x in it:
      print x, next(x);
  </code></pre>
  
  <p>Got the same error again. 
  Please help!</p>