#第四个实验-凯撒加密
#=============加密过程==============#
def encrypt(code):
work=""
for p in code:
if ord("a")<=ord(p)<=ord("z"): #小写字母加密
work+=chr(ord("a")+(ord(p)-ord("a")+3)%26)
print(chr(ord("a")+(ord(p)-ord("a")+3)%26),end='')
elif ord("A")<=ord(p)<=ord("Z"):#大写字母加密
work+=chr(ord("A")+(ord(p)-ord("A")+3)%26)
print(chr(ord("A")+(ord(p)-ord("A")+3)%26),end='')
else:
work+=p
print(p,end='')
return work #返回加密结果,方便后面解密
#============解密过程===============#
def decrypt(code):
work=""
for p in code:
if ord("a")<=ord(p)<=ord("z"): #小写字母加密
work+=chr(ord("a")+(ord(p)-ord("a")-3)%26)
print(chr(ord("a")+(ord(p)-ord("a")-3)%26),end='')
elif ord("A")<=ord(p)<=ord("Z"):#大写字母加密
work+=chr(ord("A")+(ord(p)-ord("A")-3)%26)
print(chr(ord("A")+(ord(p)-ord("A")-3)%26),end='')
else:
work+=p
print(p,end='')
return work
#======主函数:加密过程和解密过程========#
def main():
plaincode=input('请输入明文:')
work1=encrypt(plaincode)
print('\n')
decode=decrypt(work1)
main()