Re: [Python-Dev] Pep 550 and None/masking

2017-08-28 Thread Guido van Rossum
On Mon, Aug 28, 2017 at 9:26 AM, Barry Warsaw wrote: > On Aug 28, 2017, at 11:50, Yury Selivanov wrote: > > > For checking if a context variable has a value in the topmost LC, we > > can add two new keyword arguments to the "ContextVar.lookup()"

Re: [Python-Dev] Pep 550 and None/masking

2017-08-28 Thread Barry Warsaw
On Aug 28, 2017, at 11:50, Yury Selivanov wrote: > For checking if a context variable has a value in the topmost LC, we > can add two new keyword arguments to the "ContextVar.lookup()" method: > > ContextVar.lookup(*, default=None, topmost=False) > > If `topmost` is

Re: [Python-Dev] Pep 550 and None/masking

2017-08-28 Thread Yury Selivanov
On Sun, Aug 27, 2017 at 4:01 PM, Nathaniel Smith wrote: > I believe that the current status is: > > - assigning None isn't treated specially – it does mask any underlying > values (which I think is what we want) Correct. > > - there is currently no way to "unmask" > > - but it's

Re: [Python-Dev] Pep 550 and None/masking

2017-08-27 Thread Nathaniel Smith
I believe that the current status is: - assigning None isn't treated specially – it does mask any underlying values (which I think is what we want) - there is currently no way to "unmask" - but it's generally agreed that there should be a way to do that, at least in some cases, to handle the

Re: [Python-Dev] Pep 550 and None/masking

2017-08-27 Thread Ethan Furman
On 08/27/2017 11:02 AM, Chris Jerdonek wrote: Hi Jim, it seems like each time you reply you change the subject line and start a new thread. Very few others are doing this (e.g. Yury when releasing a new version). Would it be possible for you to preserve the threading like others? I must

Re: [Python-Dev] Pep 550 and None/masking

2017-08-27 Thread Chris Jerdonek
Hi Jim, it seems like each time you reply you change the subject line and start a new thread. Very few others are doing this (e.g. Yury when releasing a new version). Would it be possible for you to preserve the threading like others? --Chris On Sun, Aug 27, 2017 at 9:08 AM Jim J. Jewett

[Python-Dev] Pep 550 and None/masking

2017-08-27 Thread Jim J. Jewett
Does setting an ImplicitScopeVar to None set the value to None, or just remove it? If it removes it, does that effectively unmask a previously masked value? If it really sets to None, then is there a way to explicitly unmask previously masked values? Perhaps the initial constructor should