Makes sense. Thanks for the clarification! On Wed, Jan 1, 2020 at 1:30 AM Nick Coghlan <ncogh...@gmail.com> wrote:
> On Wed, 1 Jan 2020 at 10:42, Yonatan Zunger <zun...@humu.com> wrote: > > > > Thanks for writing this up, Nick! > > > > My main question is about the remaining difference between semantics at > the class/module versus function level: is it worth the additional > cognitive complexity to have the class/module behavior be different from > the function behavior? > > Mutating values through locals() has long worked at class and module > scope, and folks rely on that often enough that we don't want to break > their code. Correctly supporting mutation via locals() also falls > naturally out of the runtime semantics of those scopes (at module > scope, locals() returns the same namespace as globals() does, while at > class scope it returns the same namespace as will eventually be passed > to the metaclass to create the new class object). > > By contrast, mutation via locals() at function scope hasn't worked > consistently since fast locals were introduced, and that predates even > statically nested scopes (I went trawling through the repo history to > try to work out when they were first added, and made it as far as > "some time before 1997, since [1] changed how they worked to make them > faster, but was replacing an even older list-based mechanism"). > > Cheers, > Nick. > > [1] > https://github.com/python/cpython/commit/f3e85a0356e679ed9ff8d13236ff8e9f77a9fd0b#diff-f1de0b7194da5b0cdf48379eca8678d7 > > -- > Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia >
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