title: In Numpy, find Euclidean distance between each pair from two arrays
body: <p>I have two arrays of 2D coordinate points (x,y)</p>
  
  <pre><code>a = [ (x1,y1), (x2,y2), ... (xN,yN) ]
  b = [ (X1,Y1), (X2,Y2), ... (XN,YN) ]
  </code></pre>
  
  <p>How can I find the Euclidean distances between each aligned pairs <code>(xi,yi) to (Xi,Yi)</code> in an <code>1xN</code> array? </p>
  
  <p>The <code>scipy.spatial.cdist</code> function gives me distances between all pairs in an <code>NxN</code> array. </p>
  
  <p>If I just use <code>norm</code> function to calculate the distance one by one it seems to be slow. </p>
  
  <p>Is there a built in function to do this?</p>