[Python-ideas] Bytestrings in Python 2

[Serhiy Storchaka]

Here is an idea that perhaps will help to prepare Python 2 code for 
converting to Python 3.

Currently bytes is just an alias of str in Python 2, and the "b" prefix 
of string literals is ignored. There are no differences between natural 
strings and bytes. I propose to add special bit to str instances and set 
it for bytes literals and strings created from binary sources (read from 
binary files, received from sockets, the result of unicode.encode() and 
struct.pack(), etc). With -3 flag operations with binary strings that 
doesn't allowed for bytes in Python 3 (e.g. encoding or coercing to 
unicode) will emit a warning. Unfortunately we can't change the bytes 
constructor in minor version, it should left an alias to str in 2.7. So 
the result of bytes() will be not tagged as binary string.

May be it is too late for this.