[프로그래머스][Python] 시저 암호

def solution(s, n):
    alpha = "abcdefghijklmnopqrstuvwxyz"
    alpha1 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    answer=""
    for i,j in enumerate(s):
        
        if j.isupper():
            index=alpha1.index(j)+n
            answer+=alpha1[index%26]
        elif j.islower():
            index =alpha.index(j)+n
            answer+=alpha[index%26]
        else:
            answer +=" "
    return answer