title: Prevent user from entering the same input twice
body: <p>I am making a game similar to text twist on python and I was wondering how to prevent the user being able to input the same word twice. Here is what I have so far... </p>
  
  <pre><code>import random
  correct = 0
  incorrect = 0
  usedwords = []
  print 'Welcome to text twist, you have 14 guesses to get 7 words made up of 4, 5 or 6 letters. Good Luck!'
  
  for i in range(14):
      print "Your letters are 'E' 'P' 'L' 'B' 'E' 'B', what is your guess?"
      answer = raw_input()
      if answer in usedwords:
          print "Sorry, you've already used this word"
      if answer == 'belle' or answer == 'bleep' or answer == 'pebble' or answer == 'beep' or answer == 'bell' or answer == 'peel' or answer == 'peep':
          if answer in usedwords:
              print 'Nice that was one of the words!'
          usedwords.append(answer)
          correct = correct + 1
      if answer != 'belle' and answer != 'bleep' and answer != 'pebble' and answer != 'beep' and answer != 'bell' and answer != 'peel' and answer != 'peep':
          print 'Sorry, that was not one of the words.'
          incorrect = incorrect + 1
  
  
  print 'Your final score was', correct, 'correct and', incorrect, 'wrong.'
  </code></pre>