Yes, it would mean that, which is particularly nasty considering the fact that `_` in python and `Out` in IPython would then acquire the very reference that was being deleted. I think that my proposed change would be unacceptable without addressing this problem.
To resolve this, `del` could be made both a statement and an expression. The parsing rules would be very similar to how the walrus operator is handled today, but instead of being a SyntaxError in statement mode, it would simply produce a different ast node: * `del x` -> `Delete(x)` (as `x := 0` -> SyntaxError) * `(del x)` -> `Expr(DeleteExpr(x))` (as `(x := 0)` -> `Expr(NamedExpr(...))`) Eric On Fri, 12 Jun 2020 at 17:21, Guido van Rossum <gu...@python.org> wrote: > On Fri, Jun 12, 2020 at 4:55 AM Eric Wieser <wieser.eric+nu...@gmail.com> > wrote: > >> > He thought that the change of del he proposed will give him that >> behavior, but this is not true. >> >> Unless I'm forgetting part of the conversation, that's not true. Note >> that the numpy patch is merged. Today, you get the optimization with `z = a >> + b + c + d`. What you don't get is the same optimization if you use: >> ``` >> ab = a + b >> abc = ab + c >> z = abc + d >> ``` >> The language feature I propose is to allow you to _keep_ the optimization >> that was present in `z = a + b + c + d`, but write it as >> ``` >> ab = a + b >> abc = (del ab) + c >> z = (del abc) + d >> ``` >> > > But does that mean that typing `del x` at the REPL will print the value of > `x`? That seems wrong. If `del x` is an expression that returns the value > of `x` (and then unbinds it), then the REPL would seem to have no choice > but to print the returned value -- the REPL has no indication that it came > from `del`. > > -- > --Guido van Rossum (python.org/~guido) > *Pronouns: he/him **(why is my pronoun here?)* > <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/> >
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