[Python-ideas] making a module callable

[Nick Coghlan]

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.

Cheers,
Nick.

>
> --
> ~Ethan~
>
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