fr = open('12333.txt',mode='r',encoding='utf-8')
plaincode = fr.read()
print('明文:' + plaincode)
print('密文:',end='')
for c in plaincode:
print(chr(ord(c)+3),end='')
fr = open('12333.txt',mode='r',encoding='utf-8')
plaincode = fr.read()
fr.close
fw = open('c_12333.txt',mode='a',encoding='utf-8')
for c in plaincode:
fw.write(chr(ord(c)+3))
fw.close
fr = open('12333.txt',mode='r',encoding='utf-8')
plaincode = fr.read()
fr.close
fw = open('c_12333.txt',mode='a',encoding='utf-8')
for c in plaincode:
fw.write(chr(ord(c)-3))
fw.close