Ошибка при компиляции

def cypherator(text,shift):
    cypher = ""
    abc = ['q','w','e','r','t','y','u','i','o','p','a','s','d','f','g','h','j','k','l','z','x','c','v','b','n','m','q','w','e']
    text = text.lower()
    for i in range(0,len(text)):
        letter = text[i]
        try:
            res = abc[(abc.index(letter))+shift]            
        except ValueError:
            cypher+=letter
        else:
            cypher+=res
    print(cypher)
 
def decypherator(text,shift):
    decypher = ""
    abc = ['q','w','e','r','t','y','u','i','o','p','a','s','d','f','g','h','j','k','l','z','x','c','v','b','n','m','q','w','e']
    text = text.lower()
    for i in range(0,len(text)):
        letter = text[i]
        try:
            res = abc[(abc.index(letter))-shift]            
        except ValueError:
            decypher+=letter
        else:
            decypher+=res
    print(decypher)
while True:
    print("1. Cypherator\n2.Decypherator")
    a = input()
    if a == "1":
        print("Write your text here: ")
        text = input()
        shift = int(input("Shift = "))
        cypherator(text,shift)
    elif a =="2":
        print("Write your text here: ")
        text = input()
        shift = int(input("Shift = "))
        decypherator(text,shift)
    else :
        print("1. Cypherator\n2.Decypherator")