title: Change 1's to 0 and 0's to 1 in numpy array without looping
body: <p>Let's say I have a numpy array where I would like to swap all the 1's to 0 and all the 0's to 1 (the array will have other values, and there is nothing special about the 0's and 1's). Of course, I can loop through the array and change the values one by one.</p>
  <p>Is there an efficient method you can recommend using? Does the <code>np.where()</code> method have an option for this operation?</p>