k2.py

from string import ascii_lowercase
code = {
    'a':'b', 'b':'c', 'c':'d', 'd':'e', 'e':'f', 'f':'g', 'g': 'h', 'h': 'i', 'i': 'j', 'j': 'k', 'k' : 'l', 'l' : 'm',
    'm' :'n', 'n' :'o', 'o': 'p', 'p':'q', 'q' : 'r', 'r': 's', 's': 't', 't' : 'u', 'u':'v', 'v': 'w', 'w':'x',
    'x' : 'y', 'y' : 'z', 'z' : 'a', ' ': ' '
}

allowedchars = ascii_lowercase + ' '

def changer(a,b):
    code[a] = b
    return code

def taker():
    put = input("Enter Text ")
    put = put.lower()
    for i in put:
        if i in allowedchars:
            print(code[i], end='')
        elif put == '!!!':
            return
        else:
            raise Exception("404")
    print()

def changing():
    fromletter = input ("Enter Base Letter ")
    toletter = input ("Enter to Change")
    code = changer(fromletter, toletter)


def show_code():
    for k, v in code.items():
        print(k, v)

run = True
while run:
    gamestart = input("What to do, press 1 to 2")
    if gamestart == '1':
        taker()
    elif gamestart == '2':
        changing()
    else:
        run = False