title: substring not found error?
body: <p>When I run my code I get the error substring not found, I've looked through the code multiple times and don't understand what is wrong with it and how to fix it? Thankyou.</p>
  
  <p>Code:</p>
  
  <pre><code>key = "cats"
  tkey = ""
  message = "Are awesome animals!"
  alphabet = 'abcdefghijklmnopqrstuvwxyz'
  for p,k in zip(message,key):
      char = alphabet.index(p)
      temp = alphabet.index(k)
      newchar = char + temp
      if newchar &gt; 25:
          newchar -= 25
      newchar = alphabet[newchar]
      tkey.append(newchar)
  print (newchar)
  </code></pre>