title: move rows to the first row (as new columns) pandas
body: <p>I'm kind of new to <code>pandas</code> and I'm trying to perform some table manipulation. I'm not exactly sure how the action I'm looking for is called.</p>
  
  <p>I have a pandas dataframe (the actual one is larger, but these are the cols I need to convert:</p>
  
  <pre><code>   pr10      pr50      pr90
  25.6214   30.2753    36.634
  1.94509   3.84798   6.55111
        0         0   0.00835
        0         0  0.007279
  </code></pre>
  
  <p>And I want to convert it to:</p>
  
  <pre><code>pr10_0  pr50_0  pr90_0  pr10_1  pr50_1  pr90_1  pr10_2  pr50_2  pr90_2  pr10_3  pr50_3  pr90_3  pr10_4  pr50_4  pr90_4
  25.6214 30.2753 36.634  1.94509 3.84798 6.55111 0   0   0.00835 0   0   0.007279    0.003505    0.007009    0.014764
  </code></pre>
  
  <p>How can I accomplish that?</p>