Python3自定义解码

Question

When i migrate my code from python2 to python3.My code is not producing desired result instead it generate error: code snippet and error log as shown below.

import os
import sys
import base64
def decode(key, enc):
    dec = []
    enc = base64.urlsafe_b64decode(enc)
    print(enc)
    for i in range(len(enc)):
        key_c = key[i % len(key)]
        print(key_c)
        dec_c = chr((256 + ord(enc[i]) - ord(key_c)) % 256)
        print(dec_c)
        dec.append(dec_c)
    return "".join(dec)

contents = "p6KisaignLOinZqgmqKin6OT0uTZ0tSTlaKmpI+klJ+loI"
decodedLicense = decode('crab',contents)

Error Log:

File "s.py", line 16, in decode
    dec_c = chr((256 + ord(enc[i]) - ord(key_c)) % 256)
TypeError: ord() expected string of length 1, but int found

Answer 1

I have no idea if the final result is correct since you didn't indicate what the desired or expected output was in your question, which makes that very difficult to determine.

Anyhow, as I said in a comment, initially I was getting a different error complaining about the the length of contents having Incorrect padding , so the first thing I did was add something to fix that. Afterwards. I started getting the TypeError: ord() expected string of length 1, but int found exception you did mention in your question.

That was fixed by just using the bytes that base64.urlsafe_b64decode() returned direct and not trying to take their ord() .

Here's code with these changes made that at least runs...:

import os
import sys
import base64

def decode(key, enc):
    dec = []
    enc = base64.urlsafe_b64decode(enc).decode('latin1')
    for i in range(len(enc)):
        key_c = key[i % len(key)]
        dec_c = chr((256 + enc[i] - ord(key_c)) % 256)  # ord(enc[i]) -> enc[i]
        dec.append(dec_c)

    return "".join(dec)

contents = "p6KisaignLOinZqgmqKin6OT0uTZ0tSTlaKmpI+klJ+loI"  # 46 chars

# Pad contents so its length is a multiple of 3 and it's valid Base64 data.
contents = contents + {0: '', 1: '==', 2: '='}[len(contents) % 3]

decodedLicense = decode('crab', contents)
print(decodedLicense)  # -> D0AOE.;Q?+9>70A=@!q?v`s120EB,23=B.