title: Count occurrences of each key in python dictionary
body: <p>I have a python dictionary object that looks somewhat like this:</p>
  
  <pre><code>[{"house": 4,  "sign": "Aquarius"},
   {"house": 2,  "sign": "Sagittarius"},
   {"house": 8,  "sign": "Gemini"},
   {"house": 3,  "sign": "Capricorn"},
   {"house": 2,  "sign": "Sagittarius"},
   {"house": 3,  "sign": "Capricorn"},
   {"house": 10, "sign": "Leo"},
   {"house": 4,  "sign": "Aquarius"},
   {"house": 10, "sign": "Leo"},
   {"house": 1,  "sign": "Scorpio"}]
  </code></pre>
  
  <p>Now for each 'sign' key, I'd like to count how many times each value occurs.</p>
  
  <pre><code>def predominant_sign(data):
      signs = [k['sign'] for k in data if k.get('sign')]
      print len(signs)
  </code></pre>
  
  <p>This however, prints number of times 'sign' appears in the dictionary, instead of getting the value of the <code>sign</code> and counting the number of times a particular value appears.</p>
  
  <p>For example, the output I'd like to see is:</p>
  
  <pre class="lang-none prettyprint-override"><code>Aquarius: 2
  Sagittarius: 2
  Gemini: 1
  ...
  </code></pre>
  
  <p>And so on. What should I change to get the desired output?</p>