title: Pandas DataFrame types not being set automatically
body: <p>I'm trying to create a Pandas DataFrame from some text data which I'm iterating over (it's a dump of lots of json strings from an API).</p>
  
  <p>Some of the data is small numbers, eg <code>0.00000001</code>. I'm using the Python Decimal type for these elsewhere in another app. I'm not sure how to get Pandas to recognise that these are decimals. Whether I create Decimal objects from them first, or create a DataFrame just from the strings, Pandas creates generic <code>object</code> columns. There are other columns which are different formats.</p>
  
  <p>To take a simple example:</p>
  
  <pre><code>import pandas as pd
  df = pd.DataFrame([Decimal('0.01'),])
  df.dtypes
  </code></pre>
  
  <p>Outputs:</p>
  
  <pre><code>0    object
  dtype: object
  </code></pre>
  
  <p>Should I be using the Decimal type? Am I fundamentally misunderstanding something?</p>
  
  <p>Thanks.</p>