title: Extract json objects from a list using python
body: <p>I have a string type column which contains a list of elements which are nested dictionary objects. E.g</p>
  
  <pre><code>str = '[{"method":
  {"super":0.03,"normal":0.8,"par":0.15,"goal":0.01,"fact":0.04},
  "city":["nyc","atlanta"],
  "description":"some description",
  "content_type":"media"},
  {"method":
  {"super":0.03,"normal":0.8,"par":0.15,"goal":0.01,"fact":0.04},
  "city":["chicago","dallas"],
  "description":"some description2",
  "content_type":"web"},
  {"method":
  {"super":0.03,"normal":0.8,"par":0.15,"goal":0.01,"fact":0.04},
  "city":["las vegas","buffalo"],
  "description":"some description3",
  "content_type":"media"}]'
  </code></pre>
  
  <p>This is actually a column in a spark dataframe which is of a string type. So I want to know how to convert the contents of a string into a list such that I can convert each element in the list using json.loads.</p>
  
  <p>Any idea?</p>