title: Unable to insert NA's in numpy array
body: <p>I was working on this piece of code and was stuck here. </p>
  
  <pre><code>import numpy as np
  a = np.arange(10)
  a[7:] = np.nan
  </code></pre>
  
  <p>By theory, it should insert missing values starting from index 7 until the end of the array. However, when I ran the code, some random values are inserted into the array instead of NA's.</p>
  
  <p>Can someone explain what happened here and how should I insert missing values intentionally into numpy arrays?</p>