title: zip does not work for imshow: TypeError: Image data cannot be converted to float
body: <p>I saw similar questions elsewhere, but they came from different codes. My case is to transpose the data with <code>zip</code>, then use the <code>imshow</code>:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  a=[[1,2,3],[4,5,6]]
  img_data=zip(*a)
  plt.imshow(img_data)
  </code></pre>
  
  <p>I got 
      TypeError: Image data cannot be converted to float</p>