title: How to make a checkerboard in numpy?
body: <p>I'm using numpy to initialize a pixel array to a gray checkerboard (the classic representation for "no pixels", or transparent).  It seems like there ought to be a whizzy way to do it with numpy's amazing array assignment/slicing/dicing operations, but this is the best I've come up with:</p>
  
  <pre><code>w, h = 600, 800
  sq = 15    # width of each checker-square
  self.pix = numpy.zeros((w, h, 3), dtype=numpy.uint8)
  # Make a checkerboard
  row = [[(0x99,0x99,0x99),(0xAA,0xAA,0xAA)][(i//sq)%2] for i in range(w)]
  self.pix[[i for i in range(h) if (i//sq)%2 == 0]] = row
  row = [[(0xAA,0xAA,0xAA),(0x99,0x99,0x99)][(i//sq)%2] for i in range(w)]
  self.pix[[i for i in range(h) if (i//sq)%2 == 1]] = row
  </code></pre>
  
  <p>It works, but I was hoping for something simpler.</p>