title: Using not equal and nan together in python
body: <p>I have strange problem. I have the following code </p>
  
  <pre><code>if Group[NN1,8] != 'nan' :
      print("Group[NN1,8]",Group[NN1,8])
  </code></pre>
  
  <p>The value of Group[NN1,8] is nan,therefor i expect that print command not execute. But with my code it executes.
  Result is </p>
  
  <pre><code>`('Group[NN1,8]', nan)`.
  </code></pre>
  
  <p>which doesn't have to print.  Is there any thing wrong?</p>