title: Validate user input using regular expressions
body: <p>I would like to be able to validate that the user has entered a valid name within my program.  If they have not entered a valid name i want the program to continue to prompt them to enter their name again.  If the name entered is valid i would like the program to greet the user.</p>
  
  <p>So far i have: </p>
  
  <pre><code>import re
  
  user_name = input("Please enter your name: ")
  if not re.match("^[A-Za-z]*$", user_name):
      print ("Error! Make sure you only use letters in your name")
  else:
      print("Hello "+ user_name)
  </code></pre>
  
  <p>How would i loop this if their name is not valid??</p>