title: Add "nan" to numpy array 20 times without loop
body: <p>Here is my code:</p>
  
  <pre><code>import numpy as np
  n = np.array([1.1,2.3,3.4])
  for x in range(20):
      n = np.append(n, [np.nan])
  </code></pre>
  
  <p>How can I add <code>nan</code> to my <code>numpy</code> array 20 times without a loop, only using <code>numpy</code>'s tools?</p>
  
  <p>Thanks</p>