[Python-Dev] bytes type discussion

["Martin v. Löwis"]

Bob Ippolito wrote:
>>Martin von Loewis's alternative for the "very controversial" set is to
>>disallow an encoding argument and (I believe) also to disallow Unicode
>>arguments. In 3.0 this would leave us with s.encode(<encoding>) as the
>>only way to convert a string (which is always unicode) to bytes. The
>>problem with this is that there's no code that works in both 2.x and
>>3.0.
> 
> 
> Given a base64 or hex string, how do you get a bytes object out of  
> it?  Currently str.decode('base64') and str.decode('hex') are good  
> solutions to this... but you get a str object back.

If s is a base64 string,

bytes(s.decode("base64"))

should work. In 2.x, it returns a str, which is then copied into
bytes; in 3.x, .decode("base64") returns a byte string already (*),
for which an extra copy is made.

I would prefer to see base64.decodestring to return bytes,
though - perhaps even in 2.x already.

Regards,
Martin

(*) Interestingly enough, the "base64" encoding will work reversed
in terms of types, compared to all other encodings. Where .encode
returns bytes normally, it will return a string for base64, and
vice versa (assuming the bytes type has .decode/.encode methods).