title: Pandas: How can I make data frame with double columns?
body: <p>This is how data frame looks (for <code>APPL</code>):
  <a href="https://i.stack.imgur.com/ybr86.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ybr86.png" alt="enter image description here"></a></p>
  
  <p>And there is another data frame of <code>DELL</code>, having same format with above.</p>
  
  <p>What I want to create is like this:</p>
  
  <pre><code>                AAPL     |     DELL     |
              Open | Close | Open | Close |
  2011-01-01   
  2011-01-02
  2011-01-03
      .
      .
  </code></pre>
  
  <p>How can I make this kind of data frame?</p>