Yes, that's reasonable, and the PEG parser supports this (just put the `del_stmt` rule before the `expression` rule).
I'm not sponsoring your proposal though -- you're going to have to convince other core devs (and ultimately the Steering Council) that this is worth it. Once you have a core dev willing to sponsor, they can help you write a PEP. On Fri, Jun 12, 2020 at 9:36 AM Eric Wieser <wieser.eric+nu...@gmail.com> wrote: > 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/> >> > -- --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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