title: How can I iterate over a list of dicts inside a pandas dataframe?
body: <p>I have a pandas DataFrame looking something like this:</p>
  <pre><code>    | ID       | col1 | col2 |     col3    |
      | -------- | ---- | ---- | ------------|
      | ID1      | val1 | val1 | [{..},{..}] |
      | ID2      | val2 | val2 | [{..},{..}] |
  </code></pre>
  <p>the rows of col3 consist of a list of dicts looking something like this:</p>
  <pre><code>    [{'key1':'3', 'key2':'8', 'key3':'9'},
       {'key1':'3', 'key2':'8', 'key3':'7'},
       {'key1':'2', 'key2':'1', 'key3':'9'}]
  </code></pre>
  <p>The keys within all dicts are the 'same' and I'm trying to add a new column &quot;col4&quot; to my df with a count of e.g. how often the number 8 as value apears in each dict with key2 as key, similar like:</p>
  <pre><code>    | ID       | col1 | col2 |     col3    | col4 |
      | -------- | ---- | ---- | ------------| ---- |
      | ID1      | val1 | val1 | [{..},{..}] |  2   |
      | ID2      | val2 | val2 | [{..},{..}] |  5   |
  </code></pre>
  <p>I don't have any idea how to even start solving this problem, how can I iterate over a list of dicts inside a pandas dataframe?</p>