On Fri, Mar 13, 2020 at 4:04 AM Paul Moore <p.f.mo...@gmail.com> wrote: > > On Thu, 12 Mar 2020 at 16:42, Eric Wieser <wieser.eric+nu...@gmail.com> wrote: > > > > Do you have an example of an application where this sort of > > > micro-optimisation is significant enough to justify a fairly major > > > language change? > > > > As an example of these optimizations being valuable, see > > https://github.com/numpy/numpy/pull/7997, which claims the optimization I > > described at the beginning resulted in a 1.5x-2x speedup. > > I was amused by the first comment in that thread: "First, let me say > that this is terrifying and this comment should not be taken as > condoning it." > > > > but that didn't need a language change to implement... > > > > The language change I'm proposing isn't about _implementing_ these > > optimizations, it's about allowing users to exploit them without having to > > sacrifice naming their variables. > > Fair point. But I still question the cost vs benefit of this. After > all, this is a *language* change you're proposing - not just limited > to CPython with its particular implementation of GC. Consider > > x = some_complex_object() > y = (del x) > > What is to stop a Python implementation (not CPython, maybe, but some > other one) from discarding the object in x as soon as it's > unreferenced by the (del x) expression? Then y wouldn't be able to > hold that value. After all, in theory, after the first line our object > has a refcount of 1, then the (del x) changes that refcount to 0, then > y = (the value) changes it back to 1. But it could be discarded in > that period when it has refcount 0.
No, it wouldn't - the use of the value as a return value counts as a reference. It's exactly the same as any other function that returns a brand-new value. ChrisA _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/ERF7V6KVOKPLFVVC5W6QEWRBRJFUW4TB/ Code of Conduct: http://python.org/psf/codeofconduct/
