title: Split Series by string length
body: <p>I have more than 1M rows and want to split a Series of strings like <code>123456789</code> (length=9) into 3 Series (like MS Excel can do):</p>
  
  <pre><code>c1  c2  c3
  123 456 789
  ... ... ...
  </code></pre>
  
  <p>I see <code>.str.split</code> function which needs some separator and <code>.str.slice</code> which gives only one Series at a time. Is there smth. better than this?</p>
  
  <pre><code>s21 = s11.str.slice(0,3)
  s22 = s11.str.slice(3,6)
  s23 = s11.str.slice(6,9)
  </code></pre>