Yup. At least such code will not break in 3.5. In general if you write code using a newer version you should expect arbitrary breakage when trying to run it under older versions. There is no compatibility guarantee in that direction for anything anyways.
I don't see this as a reason to not put this into the language spec at 3.7. On Sun, Nov 5, 2017 at 9:37 AM, Barry Warsaw <ba...@python.org> wrote: > On Nov 4, 2017, at 11:35, Guido van Rossum <gu...@python.org> wrote: > > > > This sounds reasonable -- I think when we introduced this in 3.6 we were > worried that other implementations (e.g. Jython) would have a problem with > this, but AFAIK they've reported back that they can do this just fine. So > let's just document this as a language guarantee. > > The other concern was backward compatibility issues. For example, if 3.7 > makes this guarantee official, and folks write code with this assumption > that has to work with older versions of Python, then that code could be > buggy in previous versions and work in 3.7. This will probably be most > evident in test suites, and such failures are often mysterious to debug (as > we’ve seen in the past). > > That doesn’t mean we shouldn’t do it, but it does mean we have to be > careful and explicit to educate users about how to write safe > multi-Python-version code. > > Cheers, > -Barry > > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: https://mail.python.org/mailman/options/python-dev/ > guido%40python.org > > -- --Guido van Rossum (python.org/~guido)
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