title: Exclude items from one list based on second list in Python
body: <p>I've searched for more than an hour and haven't found exactly the solution to this, but it likely has been asked - any pointers are very welcome. </p>
  
  <p>I have time series data (time, flux) with gaps from the Kepler satellite.  I filled in missing points so I could apply a Fourier high-pass filter.  Now I want to delete the filled points from the filtered data (time, flux_residuals) so I have only the time values that were in the original data.</p>
  
  <p>So as a parallel example, say that my original data and filtered data are:</p>
  
  <pre><code>xorig = np.array([1,2,5,6]) 
  yorig = (doesn't matter)
  
  xf = np.array([1,2,3,4,5,6]) 
  yf = xf + 10
  </code></pre>
  
  <p>What is a pythonic way to extract the elements in yf where corresponding elements of xf are in xorig?</p>
  
  <pre><code>[11,12,15,16]
  </code></pre>