[Python-Dev] pathlib - current status of discussions

[Ethan Furman]

On 04/14/2016 12:03 AM, Michael Mysinger via Python-Dev wrote:
> Brett Cannon writes:

> After playing with and considering the 4 possibilities, anything where
> __fspath__ can return bytes seems like insanity that flies in the face of
> everything Python 3 is trying to accomplish. In particular, one RichPath
> class might return bytes and another str, or even worse the same class might
> sometimes return bytes and sometimes str. When will os.path.join blow up due
> to mixing bytes and str and when will it work in those situations?

What are you asking here?  Exactly where in os.join mixing bytes & str 
the exception will occur, or will mixing bytes & str ever work?

The answer to the first is irrelevant (except for performance).

The answer to the second is always/never.  Meaning allowing os.fspath() 
and __fspath__ to return either bytes or str will never cause the 
combination of bytes and str to work.  Said another way: if you are 
using os.path.join then all the pieces have be str or all the pieces 
have to be bytes.

--
~Ethan~