[Python-porting] builtins.str return type in py2

[Lennart Regebro]

At this point, I would not bother about backporting to Python 2. You
can either add Python 3 support to your existing Python 2 code to make
the library support both versions with the same code, or just move to
Python 3 and drop Python 2 support. All that means is that Python 2
users will have to stay on the current release for the remaining 370
days that Python 2 is still supported. By then they should have moved
off Python 2, and there is no reason to support Python 2 beyond that
at all.

My personal opinion and experience about the python-future package is
that it's best avoided. YMMV.

On Sun, Dec 23, 2018 at 1:23 PM Justin Israel <justinisrael at gmail.com> wrote:
>
> Hi,
>
> I've just been digging into future for one of my existing python2 libraries that needs py3 support. One thing I am wondering is about the compatability of the builtins.str type on python2. I have reviewed the API documentation (http://python-future.org/str_object.html)
>
> It seems like part of the documentation describes the backported py2 class as wanting to remain compatable with py2, while part of it says it follows the py3 functionality. I have a usage of str.translate in my library, and they have different signatures:
>
> py2
> S.translate(table [,deletechars]) -> string
>
> py3
> S.translate(table) -> str
>
> with builtins.str following the py3 signature.
> So it makes me wonder what I should be expecting if I import the builtins.str type and allow it to be returned to users of the library. Is it expected that a user of a library providing py2/3 support via future might return string types that aren't fully compatible with python2 code? What if a user tries to call str.translate on the returned string, or some other method that happens to follow the py3 signature?
>
> Looking for a little extra guidance on the best practices around returning these backported builtins to py2 users.
>
> Thanks!
> Justin
>
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