title: How to combine two dicts by key in python?
body: <p>I have two dicts built like this:  </p>
  
  <p>Dict-1:</p>
  
  <pre><code>{A:{'a1':10,'a2':20},B:{'b1':10,'b2':20}}
  </code></pre>
  
  <p>Dict-2:</p>
  
  <pre><code>{A:{'a3':30},B:{'b3':30},C:{'c1':100}}
  </code></pre>
  
  <p>I want to combine them this way:</p>
  
  <pre><code>{A:{'a1':10,'a2':20,'a3':30},B:{'b1':10,'b2':20,'b3':30},C:{'c1':100}}
  </code></pre>