Python2 fork with backwards compatible Python3 features

stefantalpalaru · n00b Joined: 11 Jan 2009 Posts: 24 Location: Italy

Unfortunately, the project's name is still undecided: https://github.com/naftaliharris/placeholder/issues/47

If you don't mind having to go through a rename, eventually, there's an experimental ebuild in my overlay: https://github.com/stefantalpalaru/gentoo-overlay/tree/master/dev-lang/py28

with a modified python-utils-r1.eclass to go with it - https://github.com/stefantalpalaru/gentoo-overlay/tree/master/eclass

So far I've tested pycairo with "py2_8" in PYTHON_TARGETS (by copying the latest "pycairo" and "python-exec" ebuilds in the local overlay so its eclass override takes precedence). Everything works as it should.

Naib · Posted: Mon Jan 30, 2017 7:55 pm Post subject:

but ... why
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stefantalpalaru · n00b Joined: 11 Jan 2009 Posts: 24 Location: Italy

Because Gentoo is about choice ;-)

Naib · Posted: Mon Jan 30, 2017 10:06 pm Post subject:

This was more todo with the entire concept of py28.
Backporting py3* features seems counter intuitive.

There were some low level PY instruction set issues that prompted the break
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stefantalpalaru · n00b Joined: 11 Jan 2009 Posts: 24 Location: Italy

It makes perfect sense to have Python3 features backported in a backwards compatible way when you have a large Python2 code base. See Perl5 vs. Perl6 for the same scenario.

Hu · Moderator Joined: 06 Mar 2007 Posts: 21633

There are valid Python2 programs that are not valid Python3 programs. Some of the non-Python3 constructs cannot readily be detected through static analysis, and must be found by running the code with appropriate inputs. For large programs without exhaustive test suites, this is impractical. Thus, some projects have opted not to support any Python that rejects any valid Python2 program. Sometimes, this is because they cannot determine if their program is valid Python3. Other times, it is because they know it is not valid Python3 and lack the resources to readily update it to become valid Python3.

Placeholder attempts to provide an interpreter that will accept all valid Python2 programs, while still providing some of the niceties that were added to Python3, but not backported by the core Python developers.

stefantalpalaru · n00b Joined: 11 Jan 2009 Posts: 24 Location: Italy

Package renamed to dev-lang/tauthon - https://github.com/stefantalpalaru/gentoo-overlay/blob/master/dev-lang/tauthon