title: Finding unique combinations of columns from a dataframe
body: <p>In my below data set, I need to find unique sequences and assign them a serial no .. </p>
  
  <p>DataSet :</p>
  
  <pre><code>user    age maritalstatus   product
  A   Young   married 111
  B   young   married 222
  C   young   Single  111
  D   old single  222
  E   old married 111
  F   teen    married 222
  G   teen    married 555
  H   adult   single  444
  I   adult   single  333
  </code></pre>
  
  <p>Expected output:</p>
  
  <pre><code>young   married     0
  young   single      1
  old     single      2
  old     married     3
  teen    married     4
  adult   single      5
  </code></pre>
  
  <p>After finding the unique values like shown above, if I pass a new user like below, </p>
  
  <pre><code>user age maritalstatus  
  X     young  married 
  </code></pre>
  
  <p>it should return me the products as a list .</p>
  
  <pre><code>X : [111, 222]
  </code></pre>
  
  <p>if there is no sequence, like below</p>
  
  <pre><code>user     age     maritalstatus  
      Y     adult  married
  </code></pre>
  
  <p>it should return me an empty list</p>
  
  <pre><code>Y : []
  </code></pre>