Simple is better than complex.
diff --git a/Lib/this.py b/Lib/this.py
index 37754b7..29e2960 100644
--- a/Lib/this.py
+++ b/Lib/this.py
@@ -20,9 +20,4 @@
 Vs gur vzcyrzragngvba vf rnfl gb rkcynva, vg znl or n tbbq vqrn.
 Anzrfcnprf ner bar ubaxvat terng vqrn -- yrg'f qb zber bs gubfr!"""
 
-d = {}
-for c in (65, 97):
-    for i in range(26):
-        d[chr(i+c)] = chr((i+13) % 26 + c)
-
-print "".join([d.get(c, c) for c in s])
+print s.decode('rot_13')