On Mon, Jul 9, 2018 at 7:40 PM, Glenn Linderman <v+pyt...@g.nevcal.com> wrote:
> On 7/9/2018 6:00 PM, Guido van Rossum wrote: > > This rule is included to simplify the choice for the user between an > assignment statements and an assignment expression -- there is no > > > "statements" should not be plural in the above line. > Will fix. syntactic position where both are valid. > > > > An exception to this special case applies when the target name is the > same as a loop control variable for a comprehension containing it. > This is invalid. This exception exists to rule out edge cases of the > above scope rules as illustrated by ``[i := i+1 for i in range(5)]`` > or ``[[(j := j) for i in range(5)] for j in range(5)]``. Note that > this exception also applies to ``[i := 0 for i, j in stuff]``, as well > as to cases like ``[i+1 for i in i := stuff]``. > > > > It is unclear whether exactly what is invalid. Is the use of the target > name that is the same as (any of the nested) loop control variable invalid? > I think, from discussions, that that is what is meant. But this paragraph > could be interpreted as meaning the special case doesn't apply, meaning > that the target name would be in a "sublocal" scope. > Really? If it didn't say "this is invalid" I could see that "exception to the special case" might be interpreted as "the special case doesn't apply". But with "This is invalid" explicitly added I don't see how that interpretation could be valid. Is it clearer if I changed that to "Such code is invalid"? Or perhaps I should move "This is invalid" to the end of the paragraph? > The ``:=`` operator groups more tightly than a comma in all syntactic > positions where it is legal, but less tightly than all operators, > > > If comma is considered an operator, this sentence is inconsistent, would > need to be "all other operators". Even if comma is not considered an > operator, the sentence would be more clear with "other" added, since ":=" > is an operator. > Makes sense. -- --Guido van Rossum (python.org/~guido)
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