title: Create Empty Dataframe in Pandas specifying column types
body: <p>I'm trying to create an empty data frame with an index and specify the column types. The way I am doing it is the following:</p>
  <pre><code>df = pd.DataFrame(index=['pbp'],
                    columns=['contract',
                             'state_and_county_code',
                             'state',
                             'county',
                             'starting_membership',
                             'starting_raw_raf',
                             'enrollment_trend',
                             'projected_membership',
                             'projected_raf'],
                    dtype=['str', 'str', 'str', 'str',
                           'int', 'float', 'float',
                           'int', 'float'])
  </code></pre>
  <p>However, I get the following error,</p>
  <pre><code>TypeError: data type not understood
  </code></pre>
  <p>What does this mean?</p>