title: How can I get the index of next non-NaN number with series in pandas?
body: <p>In pandas, I am now looping with an instance of Series, is it possible for me to know the index of the next non-NaN instantly when I meet a NaN. I don't want to skip those NaNs, because I want to do the interpolation against them.</p>
  
  <p>e.g now I have a Series <code>a</code> with elements</p>
  
  <pre><code>5, 6, 5, NaN, NaN, NaN, 7, 8, 9, NaN, NaN, NaN, 10, 10
  </code></pre>
  
  <p>The indexes of them is from 0 to 13, when I iterating the Series, when would simply love to know what is the index of the next NaN, and what is the next non-NaN. So from the beginning, can I instantly know the index of the first NaN is 4? Then when I jump to a[4], I need to know the index of the next non-NaN number, which is 6 in this case.</p>
  
  <p>Thank you so much.</p>