title: How do I combine two dataframes by both overlapping columns and indices?
body: <p>Suppose I have 2 dataframes with overlapping column and index names that look as such:</p>
  
  <pre><code>  A B C D
  A 0 1 0 1
  B 0 1 1 0
  C 1 0 1 0
  D 0 0 0 1
  
    A C D E
  A 1 0 0 0
  B 0 1 0 0
  D 0 0 0 0
  E 1 0 0 1
  </code></pre>
  
  <p>I want to combine these two dataframes into one such that cells with the same column and index names are combined. The end result should look like this:</p>
  
  <pre><code>  A B C D E
  A 1 1 0 1 0
  B 0 1 1 0 0
  C 1 0 1 0 0
  D 0 0 0 1 0
  E 1 0 0 0 1
  </code></pre>
  
  <p>I've tried using the Pandas.concat method but it only concatenates along one of the axes.</p>