Looping for every character in a string in Python decoder ring

Question

I'm trying to make a simple decoder ring in Python.

Example:

a=b, `b=c, c=d, etc.  

I want the script to take an encoded message and output the decoded message.
For instance, I would input "ifmmp" and it would output "hello".

I've been thinking I need to split all the characters up and loop through them and change their chr() or ord() values.

There doesn't seem to be any documentation for this in python.

Answer 1

How about:

s = 'ifmmp'
new_s = ''
for c in s:
    n = ord(c)
    n = n - 1
    if n < ord('a'):
        # 'a' -> 'z'
        n = ord('z')
    new_s += chr(n)
# print('new_s = %r' % new_s)  -> new_s = 'hello'

Of course, this is only handling small letters, not capital.