文件

fr = open('plainText.txt',mode='r',encoding='utf-8')
plainText = fr.read()
print(plainText)
print('密文：',end='')
for c in plainText:
    print(chr(ord(c)+3),end='')






fw =open('cipherText.txt',mode='a',encoding='utf-8')
for c in plainText:
   print(chr(ord(c)+3),end='')
   fw.write(chr(ord(c)+3))
fr.close()
fw.close()