title: Merging dictionaries function with for/in statement
body: <p>I'm a beginner in Python so I'm in need of a simple explanations.</p>
  
  <p>I have two dictionaries:</p>
  
  <pre class="lang-py prettyprint-override"><code>supply_dictionarie = {'Apple': 20, 'Cigar': 100, 'Milk': 210, 'Flower': 75}
  
  goods_dictionarie = {'Milk': 210, 'Apple': 50, 'WhiteWine': 200, 'Beer': 300, 'Oranges': 400}
  </code></pre>
  
  <p>I'm trying to merge those two dictionaries while summing the values for repeated keys. My intention is to obtain: </p>
  
  <pre><code>merged_dictionarie = {'Milk': 420, 'Cigar': 100, 'Apple': 70, 'WhiteWine': 200, 'Beer': 300, 'Oranges': 400, 'Flower': 75} *(not necessarily in this order)
  </code></pre>
  
  <p>I'm using the following code:</p>
  
  <pre class="lang-py prettyprint-override"><code>def merge_supply():
      for k in supply_dictionarie:
          if k in set(goods_dictionarie):
              merged_dictionarie[k] = goods_dictionarie.get(k, 0) + supply_dictionarie.get(k, 0)
          elif k not in set(goods_dictionarie):
              merged_dictionarie[k] = supply_dictionarie.get(k, 0)
          else:
              break
      for k in goods_dictionarie:
           if k not in set(supply_dictionarie):
              merged_dictionarie[k] = goods_dictionarie.get(k, 0)
           else:
              break
  </code></pre>
  
  <p>But all I obtain is:</p>
  
  <p><code>merged_dictionarie = {'Apple': 70, 'Cigar': 100, 'Milk': 420, 'Flower': 75}</code></p>
  
  <p>This, to me, indicates that the second "for/in" expression is not performing the job successfully. What is going wrong?</p>