title: Pandas Forward Fill NA only between two points and nothing else
body: <p>I want to use pandas forward fill null values only between two non-null data points and nothing else. </p>
  
  <p>For example I have a column named comments</p>
  
  <pre><code>Comments:
  Hello World
  NA
  Hello World
  NA 
  Hello World
  NA
  NA
  NA
  NA
  </code></pre>
  
  <p>Output should look like this:</p>
  
  <pre><code>Hello World
  Hello World
  Hello World
  Hello World
  Hello World
  NA
  NA
  NA
  NA
  </code></pre>