>>774
やってみた
def rot(x):
alphabet=['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']
return alphabet[(alphabet.index(x)+13)%26]

def rot13(X):
text = ''
for i in range(len(X)):
if X[i] in alphabet:
text += rot(X[i])
elif X[i].lower() in alphabet:
text += rot(X[i].lower()).upper()
else:
text +=X[i]
return text