title: Python - Adding two dictionaries
body: <p>How to add the values of two dictionary ?
  Ex : </p>
  
  <pre><code>a = {'a':10,'b':11,'c':20}
  b = {'a':1,'b':1,'c':1}
  </code></pre>
  
  <p>result must be</p>
  
  <pre><code>c = {'a':11,'b':12,'c':21}
  </code></pre>