[Python-ideas] Delayed Execution via Keyword

Joseph Hackman josephhackman at gmail.com
Sat Feb 18 00:34:28 EST 2017

Well, yes. I think the 'is' operator is where other attempts fall short,
and why it would require a change to Python. But yes, it would need to
force the promise.

On 17 February 2017 at 21:20, Nathaniel Smith <njs at pobox.com> wrote:

> On Thu, Feb 16, 2017 at 9:24 PM, Joseph Hackman <josephhackman at gmail.com>
> wrote:
> > Howdy All!
> >
> > This suggestion is inspired by the question on "Efficient debug logging".
> >
> > I propose a keyword to mark an expression for delayed/lazy execution, for
> > the purposes of standardizing such behavior across the language.
> >
> > The proposed format is:
> > delayed: <expr>
> > i.e. log.info("info is %s", delayed: expensiveFunction())
> People seem very excited about this as an idea, but I don't understand
> how it can be implemented.
> For example, how do you propose to handle code like this?
> value = delayed: some_dict.get("whatever")
> if value is None:
>     ...
> I.e., the question is, how does 'is' work on delayed objects? I guess
> it has to force the promise and walk the proxy chain in each input and
> then do an 'is' on the base objects? This seems like a really deep and
> confusing change to Python's object model for a pretty marginal
> feature. (This is a special case of the general observation that it's
> just not possible to implement fully-transparent proxy objects in
> Python.)
> -n
> --
> Nathaniel J. Smith -- https://vorpus.org
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