title: match pattern in pandas series
body: <p>I  have a dataframe like below,I am trying to do in python. The dataframe is formed after reading csv with the product information . The input can be of two format
  1)</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>Name</th>
  <th>Product</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>X</td>
  <td>Key1: val1, key2: val2, key3: val3</td>
  </tr>
  <tr>
  <td>Y</td>
  <td>Key1: val1, key2: val2, key3: val3</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>2)</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>Name</th>
  <th>Product</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>X</td>
  <td>[ Key1: val1, key2: val2, key3: val3</td>
  </tr>
  <tr>
  <td>Y</td>
  <td>[ Key1: val1, key2: val2, key3: val3</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>In the product series I have key, value pairs</p>
  <p>I want to store only the values of key3 in a series and remove the remaining key's and it's values.</p>
  <pre><code>import re
  regex = re.compile(r'''
      [\S]+:                
      (?:
      \s                    
          (?!\S+:)\S+       
      )+                    
      ''', re.VERBOSE)
  
  re.findall(r'key3', str(datadfnew2['Product']))
  </code></pre>
  <p>I tried to match pattern as above which is not working</p>
  <p>I want the output to look like,</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>Name</th>
  <th>Product</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>X</td>
  <td>val3</td>
  </tr>
  <tr>
  <td>Y</td>
  <td>val3</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>Please help me do that.
  Thanks</p>