I think we've debated the design of ContextVar and default values enough.
Regardless of the philosophical questions around "what is a variable", I
agree that Yury's current design is right, so let's move on to other topics
(if there are any).
On Thu, Jan 11, 2018 at 12:55 AM, Paul Moore wrote:
>
On 11 January 2018 at 07:39, Chris Jerdonek wrote:
> But to your question, like it or not, I think the API encourages this
> way of thinking because the get() method is on the ContextVar itself,
> and so it's the ContextVar which is doing the looking up rather than
> just fulfilling the role of a
On Wed, Jan 10, 2018 at 10:58 PM, Yury Selivanov
wrote:
> On Thu, Jan 11, 2018 at 10:35 AM, Chris Jerdonek
> wrote:
>> On Mon, Jan 8, 2018 at 11:02 PM, Nathaniel Smith wrote:
>>> Right now, the set of valid states for a ContextVar are: it can hold
>>> any Python object, or it can be undefined. H
On Thu, Jan 11, 2018 at 10:35 AM, Chris Jerdonek
wrote:
> On Mon, Jan 8, 2018 at 11:02 PM, Nathaniel Smith wrote:
>> Right now, the set of valid states for a ContextVar are: it can hold
>> any Python object, or it can be undefined. However, the only way it
>> can be in the "undefined" state is in
On Thu, Jan 11, 2018 at 10:39 AM, Ethan Furman wrote:
> On 01/10/2018 10:23 PM, Yury Selivanov wrote:
[..]
>> Therefore I'm still in favour of keeping the current PEP 567
>> behaviour.
>
>
> To be clear: We'll now be able to specify a default when we create the
> variable, but we can also leave i
On 01/10/2018 10:23 PM, Yury Selivanov wrote:
On Thu, Jan 11, 2018 at 4:44 AM, Nathaniel Smith wrote:
It may have gotten lost in that email, but my actual favorite approach
is that we make the signatures:
ContextVar(name, *, initial_value) # or even (*, name, initial_value)
ContextVar.get()
On Mon, Jan 8, 2018 at 11:02 PM, Nathaniel Smith wrote:
> Right now, the set of valid states for a ContextVar are: it can hold
> any Python object, or it can be undefined. However, the only way it
> can be in the "undefined" state is in a new Context where it has never
> had a value; once it leave
On Thu, Jan 11, 2018 at 4:44 AM, Nathaniel Smith wrote:
[..]
> It may have gotten lost in that email, but my actual favorite approach
> is that we make the signatures:
>
> ContextVar(name, *, initial_value) # or even (*, name, initial_value)
> ContextVar.get()
> ContextVar.set(value)
>
> so that
On 11 January 2018 at 10:44, Nathaniel Smith wrote:
> It may have gotten lost in that email, but my actual favorite approach
> is that we make the signatures:
>
> ContextVar(name, *, initial_value) # or even (*, name, initial_value)
> ContextVar.get()
> ContextVar.set(value)
>
> so that when you
On Tue, Jan 9, 2018 at 3:41 AM, Yury Selivanov wrote:
> On Tue, Jan 9, 2018 at 11:02 AM, Nathaniel Smith wrote:
>> Right now, the set of valid states for a ContextVar are: it can hold
>> any Python object, or it can be undefined. However, the only way it
>> can be in the "undefined" state is in a
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
wrote:
> By default, threading.loca
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
wrote:
> 2018-01-09 12:41
2018-01-09 12:41 GMT+01:00 Yury Selivanov :
> 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 ar
On Tue, Jan 9, 2018 at 11:02 AM, Nathaniel Smith wrote:
> On Mon, Jan 8, 2018 at 11:34 AM, Yury Selivanov
> wrote:
>> 1. Proposal: ContextVar has default set to None.
>>
>> From the typing point of view that would mean that if a context
>> variable is declared without an explicit default, its ty
On Mon, Jan 8, 2018 at 11:34 AM, Yury Selivanov wrote:
> 1. Proposal: ContextVar has default set to None.
>
> From the typing point of view that would mean that if a context
> variable is declared without an explicit default, its type would be
> Optional. E.g. say we have a hypothetical web frame
When I +1'ed Yury's message I forgot about this issue. I actually prefer
the current PEP 567 version -- .get() raises an error if there's no default
on the ContextVar, and .get(None) returns None if there's no default. The
idea here is that by far the most common use will be .get(), so it should
be
On 9 January 2018 at 05:34, Yury Selivanov wrote:
> Maybe we can rename ContextVar.get() to ContextVar.lookup()? This
> would help to avoid potential confusion between Context.get() and
> ContextVar.get().
I think this would also tie in nicely with the PEP 568 draft, where
"ContextVar.lookup()"
I am +1 on everything Yury says here.
On Mon, Jan 8, 2018 at 11:34 AM, Yury Selivanov
wrote:
> Hi,
>
> Thanks to everybody participating in the PEP 567 discussion! I want
> to summarize a few topics to make sure that we are all on the same
> page (and maybe provoke more discussion).
>
>
> 1. Pr
Hum, now I'm confused. I was probably confused by ContextVar.get()
differences with Context.get().
It's fine if it behaves with a dict.
Victor
Le 9 janv. 2018 12:02 AM, "Nathaniel Smith" a écrit :
> On Mon, Jan 8, 2018 at 2:35 PM, Victor Stinner
> wrote:
> > ctx[var] raises an exception but c
On Mon, Jan 8, 2018 at 2:35 PM, Victor Stinner wrote:
> ctx[var] raises an exception but ctx.get(var) returns None in such case. My
> point is just that Context.get() behaves differently than dict.get(). If
> dict[key] raises, I expect that dict.get() raises too and that I have to
> write explicit
Le 8 janv. 2018 8:36 PM, "Yury Selivanov" a
écrit :
2. Context.__contains__, Context.__getitem__ and ContexVar.default
So if we keep the current PEP 567 behaviour w.r.t. defaults,
ContextVar.get() might return a different value from Context.get():
v = ContextVar('v', default=42)
ctx = c
Hi,
Thanks to everybody participating in the PEP 567 discussion! I want
to summarize a few topics to make sure that we are all on the same
page (and maybe provoke more discussion).
1. Proposal: ContextVar has default set to None.
>From the typing point of view that would mean that if a context
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