title: Python: Clustering parts of list based on condition
body: <p>I have a list that is an arithmic expression, for which I want to seperate the parts that are multipying and make them a seperate list within a list</p>
  
  <pre><code> i.e. 
   ["4", "+", "5", "*", "6", "*", "7", "+", "8"]
   to 
   ["4", "+", ("5", "*", "6", "*", "7"), "+", "8"]
  </code></pre>
  
  <p>I thought of iterating over the list in steps of two (for i in l[1::2]), starting from position 1 (since a number precedes an arithmic expression) 
  and then having a 'while' condition. However I don't know how to construct the while loop in such a way it returns my desired output.</p>