[Python-ideas] Code version evolver

Chris Angelico rosuav at gmail.com
Thu Mar 14 16:47:51 EDT 2019

On Fri, Mar 15, 2019 at 7:39 AM francismb <francismb at email.de> wrote:
> Hi Steven,
> On 3/12/19 12:25 AM, Steven D'Aprano wrote:
> > I don't know who you expect is using this: the Python core developers
> > responsible for adding new language features and changing the grammar,
> > or Python programmers.
> Python core devs should write the 'python_next' and 'is_python_code'
> parts that moves source code from the current version to the next if a
> backwards incompatible grammar change is needed.
> Python programmers may use the helpers to upgrade to the next version.
> > I don't know what part of the current code (current code of *what*?) is
> > supposed to be upgraded or evolved, or what you mean by that. Do you
> > mean using this to add new grammatical features to the interpreter?
> >
> > Do you mean something like 2to3? Something which transforms source code
> > written in Python?
> >
> Yes a source transformer, but to be applied to some 3.x version to move
> it to the next 3.x+1, and so on ... (instead of '2to3' a kind of
> 'nowtonext', aka 'python_next')
> Couldn't that relax the tension on doing 'backward compatibility
> changes' a bit ?

What happens when someone wants to support multiple Python versions?
"Requires Python 3.5 or newer" is easy. Forcing people to install the
correct one for each version isn't.


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