title: Aggregating cells/column in pandas dataframe
body: <p>I have a dataframe that is like this</p>
  
  <pre><code>Index Z1       Z2       Z3       Z4  
   0    A(Z1W1)  A(Z2W1)  A(Z3W1) B(Z4W2)   
   1    A(Z1W3)  B(Z2W1)  A(Z3W2) B(Z4W3)   
   2    B(Z1W1)           A(Z3W4) B(Z4W4)
   3    B(Z1W2)
  </code></pre>
  
  <p>I want to convert it to</p>
  
  <pre><code>Index   Z1              Z2        Z3                    Z4
   0      A(Z1W1,Z1W3)    A(Z2W1)   A(Z3W1,Z3W2,Z3W4)     B(Z4W2,Z4W3,Z4W4)    
   1      B(Z1W1,Z1W2)    B(Z2W1)     
  </code></pre>
  
  <p>Basically I want to aggregate the values of different cell to one cell as shown above</p>
  
  <p><strong>Edit 1</strong></p>
  
  <p>Actual column names are either two words or 3 words names and not A B 
  For example Nut Butter instead of A</p>