text: """This module contains code from
  Think Python by Allen B. Downey
  http://thinkpython.com
  
  Copyright 2012 Allen B. Downey
  License: GNU GPLv3 http://www.gnu.org/licenses/gpl.html
  
  """
  
  
  def has_duplicates(t):
      """Checks whether any element appears more than once in a sequence.
  
      Simple version using a for loop.
  
      t: sequence
      """
      d = {}
      for x in t:
          if x in d:
              return True
          d[x] = True
      return False
  
  
  def has_duplicates2(t):
      """Checks whether any element appears more than once in a sequence.
  
      Faster version using a set.
  
      t: sequence
      """
      return len(set(t)) < len(t)
  
  
  if __name__ == '__main__':
      t = [1, 2, 3]
      print has_duplicates(t)
      t.append(1)
      print has_duplicates(t)
  
      t = [1, 2, 3]
      print has_duplicates2(t)
      t.append(1)
      print has_duplicates2(t)
  
  