title: Remove coordinates from lists on Python
body: <p>This is a follow-up question from my last question:
  <a href="https://stackoverflow.com/questions/51681673/python3-numpy-np-where-error">Python3 Numpy np.where Error</a>.</p>
  
  <p>I have 2 lists like these:</p>
  
  <pre><code>x = [None,[1, 15, 175, 20],
      [150, 175, 18, 20],
      [150, 175, 18],
      [192, 150, 177],...]
  
  
  y = [None,[12, 43, 55, 231],
      [243, 334, 44, 12],
      [656, 145, 138],
      [12, 150, 177],
      [150, 177, 188],...]
  </code></pre>
  
  <p>I want to remove the <code>x</code> values lower than 30 and <code>y</code> values that correspond to the removed <code>x</code> values. (For example, <code>(x,y) = (1,12)</code> in <code>x[1]</code> and <code>y[1]</code>)</p>
  
  <p>In order to do that, I got the corrected <code>x</code> list:</p>
  
  <pre><code>In : [[v2 for v2 in v1 if v2&gt;=30] for v1 in x[1:]]
  Out: [[175], [150, 175], [150, 175], [192, 150, 177]]
  </code></pre>
  
  <p>I also got the coordinates of the remaining <code>x</code> values:</p>
  
  <pre><code>In : [(i,j) for i,v1 in enumerate(x[1:]) for j,v2 in enumerate(v1) if v2&lt;30]
  Out: [(0, 0), (0, 1), (0, 3), (1, 2), (1, 3), (2, 2)]
  </code></pre>
  
  <p>Now I want to use these coordinates to remove items from <code>y</code>.</p>
  
  <p>How can I implement this?</p>