[Python-Dev] bytes / unicode

[Terry Reedy]

On 6/21/2010 1:29 PM, P.J. Eby wrote:
> At 05:49 PM 6/21/2010 +0100, Michael Foord wrote:
>> Why is your proposed bstr wrapper not practical to implement outside
>> the core and use in your own libraries and frameworks?
>
> __contains__ doesn't have a converse operation, so you can't code a type
> that works around this (Python 3.1 shown):
>
>  >>> from os.path import join
>  >>> join(b'x','y')

>  >>> join('y',b'x')

I am really unclear what result you intend for such mixed pairs, for all 
possible mixed pairs, sensible or not. It would seem to me best to write 
your own pjoin function that did exactly what you want over the whole 
input domain.

-- 
Terry Jan Reedy