title: Finding last transaction date in a pandas data frame
body: <p>I have a Dataframe that has <code>customer_id</code>, <code>order_id</code> and <code>Transaction_Date</code>. I want to find for a given customer, what was the last transaction date.</p>
  
  <p>The output is expected to have the following: <code>customer_id</code>, <code>order_id</code>, <code>Transaction_Date</code>, <code>last_transaction_date</code>.</p>
  
  <p><a href="https://i.stack.imgur.com/MnikV.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MnikV.jpg" alt="Pandas dataframe"></a></p>