title: PANDAS GroupBy Removing Header
body: <p>I'm using the PANDAS groupBy and noticing it is removing the header name of the value I am running it on.</p>
  
  <pre><code>data = pd.read_csv("&lt;CSV FILE NAME&gt;", low_memory=False)
  print data.head()
  print data.columns
  </code></pre>
  
  <p>Gives me the following output: </p>
  
  <pre><code>        Store ID        Daily Sales
  0       4444444         436
  1       4555555          406
  2       6435353         487
  3       3421456          637
  4       1111111         516
  Index([u'Store ID', u' Daily Sales'], dtype='object')
  </code></pre>
  
  <p>When I run </p>
  
  <pre><code>data = data.groupby(['Store Number']).mean()
  print data.head()
  print data.columns
  </code></pre>
  
  <p>The output is changed to </p>
  
  <pre><code>                  Daily Sales
  Store ID             
  4166646        236.280394
  4166663        152.061884
  4166664        131.163746
  4166665        144.920044
  4166666        225.075027
  Index([u'Daily Sales'], dtype='object')
  </code></pre>
  
  <p>The Store ID header name is being added as a value and removed from the header names. What is the reason behind this and is there a fix?</p>