title: Why the object, which I read a csv file using pandas from, is TextFileReader object
body: <p>I read a csv file using pandas:</p>
  
  <pre><code>data_raw = pd.read_csv(filename, chunksize=chunksize)
  print(data_raw['id'])
  </code></pre>
  
  <p>Then, it reports TypeError:</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  TypeError: 'TextFileReader' object has no attribute '__getitem__'
  </code></pre>
  
  <p>What can I do to resolve the problem? And how can I change the data_raw into a dataFrame object?
  I use the python2.7 and pandas v0.19.1</p>