[Python-ideas] PEP 572 version 2: Statement-Local Name Bindings

Ethan Furman ethan at stoneleaf.us
Fri Mar 2 13:36:45 EST 2018

On 03/02/2018 08:04 AM, Chris Angelico wrote:
> On Sat, Mar 3, 2018 at 1:53 AM, Rhodri James wrote:
>> On 02/03/18 11:43, Chris Angelico wrote:

>>>       # Compound statements usually enclose everything...
>>>       if (re.match(...) as m):
>>>           print(m.groups(0))
>>>       print(m) # NameError
>> This (and the equivalent in while loops) is the big win in the PEP, in my
>> opinion.  The number of ugly loops I've had to write in Python because I
>> can't write "while (something_to_do() as event):"...  +1 on this.
>>>       # Using a statement-local name
>>>       stuff = [[(f(x) as y), x/y] for x in range(5)]
>> As Paul said, the asymmetry of this bothers me a lot.  It doesn't read
>> naturally to me. -1 on this.
> Interesting. I fully expected to get a lot more backlash for the
> if/while usage, but a number of people are saying that that's the only
> (or the biggest) part of this proposal that they like.

This is the part of the PEP that I really like as well -- far more useful to me than the list-comp examples.  I could 
even be +0.5 if the "if/while/for" compound statements were kept and the comprehensions dropped -- but not with leading 
dots -- I would rather do $ than . .  Kind of like decorators, they shouldn't be used all that often.


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