使用Python实现移位加密和解密

代码很简单，就不多做解释啦。主要思路是将字符串转为Ascii码，将大小写字母分别移位密钥表示的位数，然后转回字符串。需要注意的是，当秘钥大于26的时候，我使用循环将其不断减去26，直到密钥等效小于26为止。

def encrypt():
    temp = raw_input("Please input your sentence: ")
    key = int(raw_input("Please input your key: "))
    listA = map(ord,temp)
    lens = len(listA)
    for i in range(lens):
        a = listA[i]
        if 65 <= a <= 90:
            a += key
            while a > 90:
                a -= 26
        elif 97 <= a <= 122:
            a += key
            while a > 122:
                a -= 26
        listA[i] = a
    listA = map(chr,listA)
    listA = ''.join(listA)
    print listA


def unencrypt():
    temp = raw_input("Please input your sentence: ")
    key = int(raw_input("Please input your key: "))
    listA = map(ord, temp)
    lens = len(listA)

    for i in range(lens):
        a = listA[i]
        if 65 <= a <= 90:
            a -= key
            while a < 65:
                a += 26
        elif 97 <= a <= 122:
            a -= key
            while a < 97:
                a += 26
        listA[i] = a
    listA = map(chr, listA)
    listA = ''.join(listA)
    print listA


a = int(raw_input("input 0 to encrypt and 1 to unencrypt"))

if a == 0:
    encrypt()
elif a == 1:
    unencrypt()

效果