On Mon, 10 Mar 2014 14:26:14 +1100, Chris Angelico <rosuav@gmail.com> wrote:
On Mon, Mar 10, 2014 at 1:16 PM, Jim J. Jewett <jimjjewett@gmail.com> wrote:
I don't claim that syntax is perfect. I do think it is less flawed than the no-parentheses (or external parentheses) versions:
(expr1 except expr3 if expr2) expr1 except expr3 if expr2
because the tigher parentheses correctly indicate that expr2 and expr3 should be considered as a (what-to-do-in-case-of-error) group, which interacts (as a single unit) with the main expression.
But it doesn't, really. The entire set of three expressions is a single unit. You can't break out the bit inside the parens and give that a name, like you can in most places where something "acts as a single unit" to interact with something else. (Yes, there are special cases, like the syntax for constructing slice objects that works only inside square brackets. And you can't break out a function's arguments, as a unit, into a single object (the nearest is *args,**kw). I said most places, and I don't want to add more to the special-case set.)
Actually, function arguments almost aren't a special case any more:
import inspect def a(a, b=2): ... print(a, b) ... def b(c, d=3): ... print(c, d) ... sa = inspect.signature(a) print(sa) (a, b=2) ba = sa.bind(1, 2) b(*ba.args, **ba.kwargs) 1 2
Note: I said *almost* :) But the point is that we found that the fact that we couldn't give this thing in parens a name bothersome enough to partially fix it. --David