title: Renaming columns on DataFrame output of pandas.concat
body: <p>I'm construction a new DataFrame by concatenating the columns of other DataFrames, like so: </p>
  
  <pre><code>pairs = pd.concat([pos1['Close'], pos2['Close'], pos3['Close'], pos4['Close'], pos5['Close'],
                    pos6['Close'], pos7['Close']], axis=1)
  </code></pre>
  
  <p>I want to rename all of the columns of the <code>pairs</code> Dataframe to the symbol of the underlying securities. Is there a way to do this during the the concat method call? Reading through the docs on the method here <a href="http://pandas.pydata.org/pandas-docs/version/0.17.0/generated/pandas.concat.html" rel="noreferrer">http://pandas.pydata.org/pandas-docs/version/0.17.0/generated/pandas.concat.html</a> didn't give me a solid answer.</p>