title: How to get column value as percentage of other column value in pandas dataframe
body: <p>I have a question. I have a relatively huge pandas dataframe like this one:</p>
  
  <pre><code>df:
  
     Column1  Column2  Column3  Column4
  0     100      50       25       10
  1     200      100      50       10
  2     10       10       5        5
  3     20       15       10       5
  4     10       7        7        7
  </code></pre>
  
  <p>What I now would like to do with it is adding strings to each value as follows:
  For each value in Column2, add a string displaying this value as percentage of the value in Column1. Then, for all values in Columns3 until the end (ColumnN) add to each value a string displaying this value as percentage of Column2. The final result would look like this:</p>
  
  <pre><code>df:
  
         Column1  Column2      Column3       Column4
      0     100      50 (50%)     25 (50%)      10 (20%)
      1     200      100(50%)     50 (50%)      10 (10%)
      2     10       10 (100%)    5  (50%)       5 (50%)
      3     20       15 (75%)     10 (66,6%)     5 (33,3%)
      4     10       7  (70%)     7  (100%)      7 (100%)
  </code></pre>
  
  <p>My idea of finally adding the strings to the corresponding values would maybe be something like <code>df['col'] = 'str' + df['col'].astype(str)</code>, but I don't really know how to start with it, as for example getting the percentage values for each value for example. An help on this would be really appreciated.</p>