title: python string splitting
body: <p>I have an input string like this: <code>a1b2c30d40</code> and I want to tokenize the string to: <code>a, 1, b, 2, c, 30, d, 40</code>.</p>
  
  <p>I know I can read each character one by one and keep track of the previous character to determine if I should tokenize it or not (2 digits in a row means don't tokenize it) but is there a more pythonic way of doing this?</p>