[Python-ideas] making a module callable

[Gregory P. Smith]

On Wed, Nov 20, 2013 at 7:44 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:

>
> On 21 Nov 2013 13:02, "Ethan Furman" <ethan at stoneleaf.us> wrote:
> >
> > On 11/20/2013 05:57 PM, Andrew Barnert wrote:
> >
> >> On Nov 20, 2013, at 12:14, Eric Snow wrote:
> >>
> >>> In contrast, something like __metamodule__ would be an effective
> >>> replacement.  It would be similar in spirit and in syntax to
> >>> __init_class__ in PEP 422 (and __metaclass__ in Python 2), defined at
> >>> the top of the module and used for the module.  The thing that appeals
> >>> to me is that we could deprecate the sys.modules hack. :)
> >>
> >>
> >> Given that __metaclass__ was removed in Python 3, doesn't "this is an
> >>  exact parallel to __metaclass__" argue against the idea, rather than
> >>  for? Or at least against the name? (Maybe __init_module__?)
> >>
> >> Anyway, I think a module replacing itself with something callable is
> >>  both more flexible and more in line with the way people are actually
> >>  doing things today, so maybe a "less hacky" way to do the sys.modules
> >>  hack is what people actually want here.
> >
> >
> > sys.modules is a dictionary.
> >
> >     dict[name] = something
> >
> > is the normal way to set values to keys.
> >
> > What is so horrible about this idiom?
>
> It potentially causes problems for module reloading and it definitely
> causes problems for the import engine PEP (since sys.modules is process
> global state).
>
> I expect we'll revisit this later in the 3.5 development cycle (we haven't
> even merged the accepted PEP 451 for 3.4 yet), but formalising the current
> module replacement idiom is already a more likely outcome than making
> module instances callable.
>
Agreed, formalizing how to do the replacement trick sounds good. It'd be
ideal for a module to not need to know its own name within the code doing
the replacement and for it to not need to reimplement common interface bits
in a replacement class so that it quacks like a module.

Making it callable? well, that does just seem silly so I'm not actually
worried about making that specifically easier itself.


> Cheers,
> Nick.
>
> >
> > --
> > ~Ethan~
> >
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