title: Python: Pandas Dataframe is empty after adding columns
body: <p>The following code snippet</p>
  
  <pre><code>df = pandas.DataFrame({})
  for run in range(3):
       df[str(run)] = pandas.Series([1,2])
  </code></pre>
  
  <p>produces an empty dataframe (instead of three columns of [1,2], indexed by 0, 1, 2). Why, and how do I fix this?</p>
  
  <p>More precisely, this is what is output by pandas version 0.11 (run in ipython with Python 2.7): </p>
  
  <pre><code>In [17]: df
  Out[17]:
  Empty DataFrame
  Columns: [0, 1, 2]
  
  
  Index: []
  </code></pre>