title: Pandas selecting by label sometimes return Series, sometimes returns DataFrame
body: <p>In Pandas, when I select a label that only has one entry in the index I get back a Series, but when I select an entry that has more then one entry I get back a data frame.</p>
  
  <p>Why is that?  Is there a way to ensure I always get back a data frame?</p>
  
  <pre><code>In [1]: import pandas as pd
  
  In [2]: df = pd.DataFrame(data=range(5), index=[1, 2, 3, 3, 3])
  
  In [3]: type(df.loc[3])
  Out[3]: pandas.core.frame.DataFrame
  
  In [4]: type(df.loc[1])
  Out[4]: pandas.core.series.Series
  </code></pre>