title: Python - Get all values of field in JSON
body: <p>I have a geoJSON file, and I'd like to extract all the possible values in a subfield. So for a two items long json it would be like this:</p>
  
  <pre><code>data['features'][0]['properties']['cellId']
  #returns 38
  data['features'][1]['properties']['cellId']
  #returns 51
  </code></pre>
  
  <p>I'd like to return <code>[38, 51]</code>. Is it possible? I tried</p>
  
  <pre><code>data['features'][0:]['properties']['cellId']
  </code></pre>
  
  <p>but it doesn't work, since <code>TypeError: list indices must be integers or slices, not str</code></p>