title: Extract first characters from list series pandas
body: <p>I have a string series containing multiples words. I want to extract the first character of each word per row in a vectorized fashion. </p>
  
  <p>So far, I have been able to split the words into a list, but haven't found a vectorized way of getting the first characters. </p>
  
  <pre><code>s = pd.Series(['aa bb cc', 'cc dd ee', 'ff ga', '0w'])
  
  &gt;&gt;&gt; s. str.split()
  0    [aa, bb, cc]
  1    [cc, dd, ee]
  2        [ff, ga]
  3            [0w]
  </code></pre>
  
  <p>Eventually, I want something like this:</p>
  
  <pre><code>0    [a, b, c]
  1    [c, d, e]
  2       [f, g]
  3          [0]
  </code></pre>