On 25 June 2018 at 09:25, Guido van Rossum <gu...@python.org> wrote:
> A "neutral" argument about (b) is that despite the "horrified" reactions
> that Nick saw, in practice it's going to confuse very few people (again, due
> to my point about Python's scope rules). I'd wager that the people who might
> be most horrified about it would be people who feel strongly that the change
> to the comprehension scope rules in Python 3 is a big improvement, and who
> are familiar with the difference in implementation of comprehensions (though
> not generator expressions) in Python 2 vs. 3.
FWIW, the most cryptic parent local scoping related exception I've
been able to devise so far still exhibits PEP 572's desired "Omitting
the comprehension scope entirely would give you the same name lookup
behaviour" semantics:
>>> def outer(x=1):
... def middle():
... return [x := x + i for i in range(10)]
... return middle()
...
>>> outer()
Traceback (most recent call last):
...
NameError: free variable 'x' referenced before assignment in enclosing scope
It isn't the parent local scoping, or even the assignment expression,
that's at fault there, since you'd get exactly the same exception for:
def outer(x=1):
def middle():
x = x +1
return x
return middle()
Cheers,
Nick.
--
Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia
_______________________________________________
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
