title: Take a subset of dataframe as TextParser object
body: <p>I am trying to read a csv files in chunks using pandas, but would only like to take a subset of the columns. I am trying to use</p>
  
  <pre><code>df = pandas.io.parsers.read_table(myData, chunksize=1000)
  df = df[id_fields + [time_field] + value_fields]
  </code></pre>
  
  <p>But that gives me the following error:</p>
  
  <pre><code>TextFileReader' object has no attribute '__getitem__'
  </code></pre>
  
  <p>The same code works if I drop the chunksize bit:</p>
  
  <pre><code>df = pandas.io.parsers.read_table(myData)
  df = df[id_fields + [time_field] + value_fields]
  </code></pre>
  
  <p>Any ideas how to get around this?</p>
  
  <p>Thanks,
  Anne</p>