[Python-Dev] PEP 567 pre v3

[Guido van Rossum]

There are too many words here for me to follow. I'll wait a few days and
then hopefully there's a new proposal that you are all in agreement with,
or there are two brief alternatives that I have to choose between.

On Tue, Jan 9, 2018 at 7:41 AM, Yury Selivanov <yselivanov.ml at gmail.com>
wrote:

> By default, threading.local raises an AttributeError (unless you subclass
> it.)  Similar to that and to NameErrors, I think it's a good idea for
> ContextVars to raise a LookupError if a variable was not explicitly set.
>
> Yury
>
>
> On Tue, Jan 9, 2018 at 7:15 PM Victor Stinner <victor.stinner at gmail.com>
> wrote:
>
>> 2018-01-09 12:41 GMT+01:00 Yury Selivanov <yselivanov.ml at gmail.com>:
>> > But I'd be -1 on making all ContextVars have a None default
>> > (effectively have a "ContextVar.get(default=None)" signature. This
>> > would be a very loose semantics in my opinion.
>>
>> Why do you think that it's a loose semantics? For me
>> ContextVar/Context are similar to Python namespaces and thread local
>> storage.
>>
>> To "declare" a variable in a Python namespace, you have to set it:
>> "global x" doesn't create a variable, only "x = None".
>>
>> It's not possible to define a thread local variable without specifying
>> a "default" value neither.
>>
>> Victor
>>
>
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-- 
--Guido van Rossum (python.org/~guido)
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