[Nick Coghlan] > However, PEP 572 in its current form takes the position "parent local > scoping is sufficiently useful to make it a required pre-requisite for > adding assignment expressions, but not useful enough to expose as a > new scope declaration primitive", >
Of course the PEP doesn't take that position at all: it doesn't even contain the term "parent local scoping". That's your term, which nobody else uses unless they're replying to you ;-) What the PEP does say: """ an assignment expression occurring in a list, set or dict comprehension or in a generator expression (below collectively referred to as "comprehensions") binds the target in the containing scope, honoring a nonlocal or global declaration for the target in that scope, if one exists. For the purpose of this rule the containing scope of a nested comprehension is the scope that contains the outermost comprehension. A lambda counts as a containing scope. """ It's a small collection of plainly stated rules for specifying the intended semantics. If you want to claim that this _is_ "useful enough to expose as a new scope declaration primitive", it's really on you to present use cases to justify that claim. I'd present some for you, but I don't have any (I don't care that "by hand" conversion of nested comprehensions to workalike Python nested functions may require a bit of thought to establish the intended scope of assignment expression target names - all of which is easily doable without adding any new statements). I don't _expect_ that other good use cases exist. The gimmick's purpose is to make code that visually _appears_ to belong to a block act as if embedded assignments do occur in that block. If there's an explicitly nested function, that fundamental motivation no longer applies.
_______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
