title: Restacking n-columns into 3 columns Python
body: <p>I have a dataframe that looks like this (where the <strong>first row</strong> is the <strong>index number</strong>):</p>
  
  <pre><code>0      1      2      3       4       5       6        7       8
  
  66     56     34     40     41      55       80      None     None
  90     91     12     44     89      60       11      45       60
  10     20     49     90     33      40       67      55       None
  .
  .
  </code></pre>
  
  <p>What I need as an output is to take every 3rd value, <strong>ignore</strong> any <strong>None values</strong> and restack it into a single row like this:</p>
  
  <pre><code>0       1         2 
  
  66      56        34
  40      41        55
  80      90        91
  12      44        89
  60      11        45
  60      10        20
  49      90        33
  40      67        55
  </code></pre>
  
  <p>Is there an easy way to pivot and stack it this way?</p>