title: Python - counting sign changes
body: <p>I have a list of numbers I am reading left to right. Anytime I encounter a sign change when reading the sequence I want to count it. </p>
  
  <pre><code>X = [-3,2,7,-4,1,-1,1,6,-1,0,-2,1] 
  X = [-, +, +, -, +, -, +, +, -, -,-,+]
  </code></pre>
  
  <p>So, in this list there are 8 sign changes.</p>
  
  <p>When Item <code>[0]</code> (in this case -3) is negative it is considered a sign change. Also, any 0 in the list is considered <code>[-]</code>.   </p>
  
  <p>Any help would be greatly appreciated. </p>