[Python-Dev] PEP 550 v4

[Yury Selivanov]

On Sat, Aug 26, 2017 at 1:23 PM, Ethan Furman <ethan at stoneleaf.us> wrote:
> On 08/26/2017 09:25 AM, Yury Selivanov wrote:
>>
>> On Fri, Aug 25, 2017 at 10:19 PM, Ethan Furman wrote:
>
>
>>>> A *context variable* is an object representing a value in the
>>>> execution context.  A new context variable is created by calling
>>>> the ``new_context_var()`` function.  A context variable object has
>>>> two methods:
>>>>
>>>> * ``lookup()``: returns the value of the variable in the current
>>>>     execution context;
>>>>
>>>> * ``set()``: sets the value of the variable in the current
>>>>     execution context.
>>>
>>>
>>>
>>> Why "lookup" and not "get" ?  Many APIs use "get" and it's functionality
>>> is
>>> well understood.
>>
>>
>> ContextVar.set(value) method writes the `value` to the *topmost LC*.
>>
>> ContextVar.lookup() method *traverses the stack* until it finds the LC
>> that has a value.  "get()" does not reflect this subtle semantics
>> difference.
>
>
> A good point; however, ChainMap, which behaves similarly as far as lookup
> goes, uses "get" and does not have a "lookup" method.  I think we lose more
> than we gain by changing that method name.

ChainMap is constrained to be a Mapping-like object, but I get your
point.  Let's see what others say about the "lookup()".  It is kind of
an experiment to try a name and see if it fits.

Yury