title: Separate list in equal steps
body: <p>I have a list of variable size. She will always have at least three elements, and new elements are always multiples of three. </p>
  
  <p>An example list would be as follows: </p>
  
  <pre><code>['ttyUSB0', 'ttyUSB1', 'ttyUSB2', 'ttyUSB3', 'ttyUSB4',
  'ttyUSB5', 'ttyUSB6', 'ttyUSB7', 'ttyUSB8']
  </code></pre>
  
  <p>My problem is I always have to pick the second element of this trio. So, for the above list, I need to recover the following result:</p>
  
  <pre><code>['ttyUSB1', 'ttyUSB4', 'ttyUSB7']
  </code></pre>
  
  <p>The code below works perfectly, but is not elegant, someone has some more inteigente solution?</p>
  
  <pre><code>def removeUselessSerialDoors(self, devices):
  
      new_list = []
      count = 0
  
      for port in devices:
  
          if count == 0:
              pass
  
          elif count == 1:
              new_list.append(port)
  
          elif count == 2:
              count = 0
              continue
  
          count = count + 1    
  
      return new_list
  </code></pre>
  
  <p>thanks for your time</p>