title: Python get certain coordinate from list
body: <p>I have a list of coordinates,like :<code>[(1,2,3),(2,3,4),(3,4,5),(4,5,6)]</code></p>
  
  <p>I want to get certain number, like <code>x1=1</code> from <code>(1,2,3)</code>, <code>y1=2</code> from <code>(1,2,3)</code>, I don't know if it can be done.</p>
  
  <p>Because I want to calculate the distance between certain two coordinates.</p>
  
  <p>use :</p>
  
  <p><code>math.sqrt(( x1-x2 )**2 + ( y1-y2 )**2 + (z1-z2 )**2)</code></p>
  
  <p>Thank you!</p>