title: Convert a column to an index in pandas
body: <p>I have a DataFrame <code>df</code> like this.</p>
  
  <pre><code>Number SomeValue SomeOtherValue
    10    10        1.0
    11     3        1.1
  </code></pre>
  
  <p>when I look at the data frame using <code>df.head()</code>, I get this</p>
  
  <pre><code>  Number SomeValue SomeOtherValue
  0  10    10        1.0
  1  11     3        1.1
  </code></pre>
  
  <p>I would like <code>Number</code> to be my index, so I do something like this:</p>
  
  <pre><code>df.index = df.Number
  df = df.drop('Number', 1);
  </code></pre>
  
  <p>This seems a bit clumsy, so is there another way of promoting a column to an index?</p>