py2 to 3 base64 issues

[MRAB]

On 2019-08-09 17:06, Larry Martell wrote:
> I have some python 2 code:
> 
> def decode(key, string):
>         decoded_chars = []
>         string = base64.urlsafe_b64decode(string)
>         for i in range(len(string)):
>             key_c = key[i % len(key)]
>             encoded_c = chr(abs(ord(string[i]) - ord(key_c) % 256))
>             decoded_chars.append(encoded_c)
>         decoded_string = "".join(decoded_chars)
>         return decoded_string
> 
> and if I call it like this in py2 it works as expected:
> 
> s = 'V3NYVY95iImnnJWCmqphWFFzU1qvqsV6x83Mxa7HipZitZeMxbe709jJtbfW6Y6blQ=='
> key = '!@#$VERYsecRet)('
> decode(key, s)
> 
> In py3 it fails with
> 
> TypeError: ord() expected string of length 1, but int found
> 
> I know that in py3 base64.urlsafe_b64decode is returning bytes not
> chars and that is what that is happening, and I thought the solution
> would be to decode it, but what codec would I use for this?
> 
I'll use the b and u prefixes for clarity.

In Python 2, b'abc'[0] is b'a' and u'abc'[0] is u'a'.

In Python 3, b'abc'[0] is 65 and u'abc'[0] is u'a'.

Using ord on an int raises an exception.