On 26.06.2018 0:13, Steve Holden wrote:
On Mon, Jun 25, 2018 at 8:37 PM, Terry Reedy <[email protected]
<mailto:[email protected]>> wrote:
On 6/24/2018 7:25 PM, Guido van Rossum wrote:
I'd wager that the people who might be most horrified about it
the (b) scoping rule change
would be people who feel strongly that the change to the
comprehension scope rules in Python 3 is a big improvement,
I might not be one of those 'most horrified' by (b), but I
increasingly don't like it, and I was at best -0 on the
comprehension scope change. To me, iteration variable assignment
in the current scope is a non-problem. So to me the change was
mostly useless churn. Little benefit, little harm. And not worth
fighting when others saw a benefit.
However, having made the change to nested scopes, I think we
should stick with them. Or repeal them. (I believe there is
another way to isolate iteration names -- see below). To me, (b)
amounts to half repealing the nested scope change, making
comprehensions half-fowl, half-fish chimeras.
[...]
--
Terry Jan Reedy
I'd like to ask: how many readers of
this email have ever deliberately taken advantage of the limited
Python 3 scope in comprehensions and generator expressions to use what
would otherwise be a conflicting local variable name?
I did:
for l in (l.rstrip() for l in f):
The provisional unstripped line variable is totally unneeded in the
following code.
I appreciate that the scope limitation can sidestep accidental naming
errors, which is a good thing.
Unfortunately, unless we anticipate Python 4 (or whatever) also making
for loops have an implicit scope, I am left wondering whether it's not
too large a price to pay. After all, special cases aren't special
enough to break the rules, and unless the language is headed towards
implicit scope for all uses of "for" one could argue that the scope
limitation is a special case too far. It certainly threatens to be yet
another confusion for learners, and while that isn't the only
consideration, it should be given due weight.
_______________________________________________
Python-Dev mailing list
[email protected]
https://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
https://mail.python.org/mailman/options/python-dev/vano%40mail.mipt.ru
--
Regards,
Ivan
_______________________________________________
Python-Dev mailing list
[email protected]
https://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com