(original) (raw)

On Thu, Jan 4, 2018 at 9:27 AM, Paul Moore <p.f.moore@gmail.com> wrote:

On 4 January 2018 at 15:56, Guido van Rossum <guido@python.org> wrote:
\> It was get\_context() in an earlier version of PEP 567\. We changed it to
\> copy\_context() believing that that would clarify that you get a clone that
\> is unaffected by subsequent ContextVar.set() operations (which affect the
\> \*current\* context rather than the copy you just got).

Ah thanks. In which case, simply changing the emphasis to avoid the
implication that Context objects are immutable (while that may be true
in a technical/implementation sense, it's not really true in a design
sense if ContextVar.set modifies the value of a variable in a context)
is probably sufficient.

Do you have a specific proposal for a wording change? PEP 567 describes Context as "a read-only mapping, implemented using an immutable dictionary." This sounds all right to me -- "read-only" is weaker than "immutable". Maybe the implementation should not be mentioned here? (The crux here is that a given Context acts as a variable referencing an immutable dict -- but it may reference different immutable dicts at different times.)

--Guido van Rossum (python.org/\~guido)