title: Creating a column from a condition with multiple macthes per row
body: <p>Hi I have a list and a dataframe. I want to create a new column based on the matches from the list.</p>
  
  <p>I'm able to run str.extract to find matches, but it only lists the first match then moves to the next row. How can I get all of the matches in each row to appear?</p>
  
  <pre><code>my list = ['a', 'b', 'c']
  
  existing_col
     a b
     a c
  
  df2['new_col'] = df2['existing_col'].str.extract(f'({"|".join(my_list)})', expand=False) 
  
  existing_col    new_col
     a b            a 
     a b            c 
  </code></pre>
  
  <p>This is essentially the result I am returned right now.
  Thanks in advance.</p>