On Sat, Apr 28, 2018 at 2:07 AM Tim Peters <tim.pet...@gmail.com> wrote:
[...]
> Speaking of which, "sublocal" would be a more accurate name, and less
> likely to conflict with existing code names, but after people got over
> the shock to their sense of purity, they'd appreciate typing the
> shorter "local" instead ;-)
> For that matter, I'd be fine too with shortening it to "let". In
> fact, I prefer that! Thanks :-)
Great! :)
[...]
> So, curiously enough, I'd be fonder of
> result_expression "where" name=expression, ...
> than of
> "let" name=expression, ...
My gripe about the "where"-like syntax family (including "as", proposed by
many) is that the whole expression needs to be read backwards to make sense
of `name*. It's one of the things that annoy me in languages like SQL,
where the relevant "AS" keyword can be buried a couple of screens
below/above the area of interest. That's why I find the "let" form
superior.
[..]
> instead. In _an expression_, I naturally group the
> a = 3, a
> part as the unintended
> a = (3, a)
> When I'm thinking of function calls, though, I naturally use the intended
> (a=3), a
> grouping. I really don't want to fight with what "everyone already
> knows", but build on that to the extent possible.
Looking at all of these and other examples in your email I have to agree
that the version with parenthesis reads way more clearly. A different (and
correct in this case) precedence of "," between parens is pretty much
hardwired in our brains.
[..]
> Why not? A great many objects in Python are _designed_ so that their
> __bool__ method does a useful thing in a plain
> if object:
> test. In these common cases, needing to type
> if let name=object, object:
Alright. And yes, I agree, surrounding parens are badly needed. Maybe we
can replace parens with {}? Although my immediate reaction to that is "it's
too ugly to be taken seriously".
In any case, the similarity of this new syntax to a function call still
bothers me. If I just looked at some Python 3.xx code and saw the new
"let(..)" syntax, I would assume that the names it declares are only
visible *within* the parens. Parens imply some locality of whatever is
happening between them. Even if I googled the docs first to learn some
basics about "let", when I saw "if let(name...)" it wouldn't be immediately
apparent to me that `name` is set only for its "if" block (contrary to "if
let a = 1: print(a)").
Yury
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