title: Regex pattern for extracting substring from dataframe
body: <p>I have a dataframe column as follows:</p>
  <pre><code>df['col1']
  
  ['cat-dog asd-pwr sdf', 'cat-goat asd-pwr2 sdf', 'cat asd-pwr3 sdf']
  </code></pre>
  <p>I need to extract the following:</p>
  <pre><code>['asd-pwr', 'asd-pwr2', 'asd-pwr3']
  </code></pre>
  <p>i.e the last pair of substrings which are connected by <code>-</code></p>
  <p>I tried the following:</p>
  <pre><code>import re
  df['col1'].str.extract(r'\s[a-zA-Z]*-[a-zA-Z]*\s', flags=re.IGNORECASE)
  </code></pre>
  <p>First of all, my regex construct even fails to spot any pair of substrings as desired.</p>