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.stin...@gmail.com> wrote: > 2018-01-09 12:41 GMT+01:00 Yury Selivanov <yselivanov...@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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