文件操作

fr = open('plainText.txt',mode='r',encoding='utf-8')
plainText = fr.read()
print('明文：'+plainText)
print('密文：',end='' )
fw = open('cipherText.txt',mode='a',encoding='utf-8')
for c in plainText:
    print(chr(ord(c)+2),end='')
    fw.write(chr(ord(c)+2))