[Python-Dev] PEP 408 -- Standard library __preview__ package

[Matt Joiner]

> A more normal incantation, as is often the way for packages that became
> parts of the standard library after first being a third party library
> (sometimes under a different name, e.g. simplejson -> json):
>
> try:
>    from __preview__ import thing
> except ImportError:
>    import thing
>
> So no need to target a very specific version of Python.

I think this is suboptimal, having to guess where modules are located,
you end up with this in every module:

try:
    import cjson as json
except ImportError:
   try:
       import simplejson as json
  except ImportError:
      import json as json

Perhaps the versioned import stuff could be implemented (whatever the
syntax may be), in order that something like this can be done instead:

import regex('__preview__')
import regex('3.4')

Where clearly the __preview__ version makes no guarantees about
interface or implementation whatsoever.

etc.