title: using remainder to help find index?
body: <p>Can anyone explain why "%26" is needed in the following code? The result seems the same without "%26". 
  Code source <a href="https://gist.github.com/nchitalov/2f2b03e5cf1e19da1525" rel="nofollow noreferrer">enter link description here</a></p>
  
  <pre><code>def caesar_encrypt(realText, step):
      outText = []
      cryptText = []
  
      uppercase = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z']
      lowercase = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']
  
      for eachLetter in realText:
          if eachLetter in uppercase:
              index = uppercase.index(eachLetter)
              crypting = (index + step) % 26
              cryptText.append(crypting)
              newLetter = uppercase[crypting]
              outText.append(newLetter)
          elif eachLetter in lowercase:
              index = lowercase.index(eachLetter)
              crypting = (index + step) % 26
              cryptText.append(crypting)
              newLetter = lowercase[crypting]
              outText.append(newLetter)
      return outText
  
  code = caesar_encrypt('abc', 2)
  print(code)
  </code></pre>