[Python-ideas] Idea: Deferred Default Arguments?

[Peter O'Connor]

On Fri, Jul 20, 2018 at 5:41 PM, Steven D'Aprano <steve at pearwood.info>
wrote:
>
>
> What makes you think that a built-in deferred feature won't have exactly
> the same issues? Do you have an implementation that doesn't need to do
> intraspection?


I don't know about these low level things, but I assume it'd be implemented
in C and wouldn't have the same cost as entering a new function in Python.
 I imagine it just being a small modification of the mechanism that Python
already uses to assign values to arguments when a function is called.  Is
that not the case?



On Fri, Jul 20, 2018 at 5:41 PM, Steven D'Aprano <steve at pearwood.info>
wrote:

> On Fri, Jul 20, 2018 at 04:43:56PM +0200, Peter O'Connor wrote:
>
> > I still think it would be nice to have this as a built-in python feature,
> > for a few reasons:
> > - When using non-differable functions (say in other codebases), we have
> to
> > do a bunch of "func = deferrable_args(func)" at the top of the module (or
> > we can just do them at runtime, but then we're doing inspection every
> time,
> > which is probably slow).
> > - It adds a layer to the call stack for every deferrable function you're
> in.
> > - To avoid annoying errors where you've defined an arg as deferred but
> > forgot to wrap the function in question.
>
> What makes you think that a built-in deferred feature won't have exactly
> the same issues? Do you have an implementation that doesn't need to do
> intraspection?
>
>
> --
> Steve
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