Ceaser cipher not working

Ceaser cipher not working
0
#1

I am coding a ceaser cipher for my AP Computer science class but its not working. can someone please help.
The link to the code
Cypher.py

#2

It’s not working because???

#3

check below code , this is will do shift three only (i know there user input ) but later i will update it

import string
x = raw_input("inter a masseg to dycrept or incrept-->")
y = raw_input("incrypt = i  dycrept = d -->")
x = x.lower()
y = y.lower()
#------------script start-------------------------------------
def inc(x):
    result = []
    for i in x:
        try:
            o = string.ascii_lowercase.index(i)
            result.append(string.ascii_lowercase[o+3])
        except:
            if i == 'x':
                result.append("a")
            elif i == 'y':
                result.append("b")
            else:
                result.append("c")
    return result

def dyc(x):
    result = []
    for i in x[:]:
        try:
            o = string.ascii_lowercase.index(i)
            result.append(string.ascii_lowercase[o-3])
        except:
            if i == 'a':
                result.append("x")
            elif i == 'b':
                result.append("y")
            else:
                result.append("z")
    return result

if y == "i":
    print ''.join(inc(x))
if y == "d":
    print ''.join(dyc(x))