title: Separate a list based on values in a second list
body: <p>X: a list of lists, where each list element corresponds to a label in Y</p>
  
  <p>Y: a binary list of labels (values are either 1 or 0)</p>
  
  <p>I want to extract the elements in X according to the value at the corresponding index in Y, as follows:</p>
  
  <p>good = values of X where the label/value in Y is 1<br>
  bad = values of X where the label/value in Y is 0</p>
  
  <p>I am still fairly new to sub-setting in Python and not really sure of a good way to do this.</p>