title: Python rotational cipher script issue
body: <p>So basically I am writing a tool to brute force all the possible answers to a alphabet rotational cipher, then print them all out to the screen. How do I keep special characters and spaces from rotating and just leave them as they are.</p>
  
  <pre class="lang-py prettyprint-override"><code>#!/usr/bin/env python3
  
  # alphabeth and key variables
  
  import sys
  
  alpha_upper = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
  alpha_lower = "abcdefghijklmnopqrstuvwxyz"
  cipher_text = sys.argv[1]
  
  def crack_rotation():
  
      for key in range(len(alpha_lower)):
          plain_text = ''
  
          for character in cipher_text:
              if character == character.lower():
                  index = alpha_lower.find(character)
                  index = (index-key)%len(alpha_lower)
                  plain_text += alpha_lower[index]
              else:
                  index = alpha_upper.find(character)
                  index = (index-key)%len(alpha_upper)
                  plain_text += alpha_upper[index]
  
          print('Trying with key %s. Result = %s' %(key, plain_text))
  
  crack_rotation()
  </code></pre>