[Python-Dev] Smoothing the transition from Python 2 to 3

[Brett Cannon]

On Thu, 9 Jun 2016 at 14:56 Nick Coghlan <ncoghlan at gmail.com> wrote:

> On 8 June 2016 at 14:01, Neil Schemenauer <neil at python.ca> wrote:
> > [I've posted something about this on python-ideas but since I now
> > have some basic working code, I think it is more than an idea.]
> >
> > I think the uptake of Python 3 is starting to accelerate.  That's
> > good.  However, there are still millions or maybe billions of lines
> > of Python code that still needs to be ported.  It is beneficial to
> > the Python ecosystem if this code can get ported.
> >
> > My idea is to make a stepping stone version of Python, between 2.7.x
> > and 3.x that eases the porting job.  The high level goals are:
> >
> > - code coming out of 2to3 runs correctly on this modified Python
> >
> > - code that runs without warnings on this modified Python will run
> >   correctly on Python 3.x.
>
> As Victor noted, and as the porting guide describes in
> https://docs.python.org/3/howto/pyporting.html#update-your-code, we've
> determined that 2to3 isn't the best choice of tool for folks that
> can't afford to immediately drop Python 2 support.
>
> Once you switch to those now recommended more conservative migration
> tools, the tool suite you request already exists:
>
> - update your code with modernize or futurize
> - check it still runs on Python 2.7
> - check it doesn't generate warnings under 2.7's "-3" switch
> - check it passes "pylint --py3k"
> - check if it runs on Python 3.5
>

`python3.5 -bb` is best to help keep Python 2.7 compatibility, otherwise
what Nick said. :)
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