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Re: __missing__ for the top-level Python script

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  Re: __missing__ for the top-level Python script Dave Angel <davea@davea.name> - 2014-11-12 10:16 -0500

#80609 — Re: __missing__ for the top-level Python script

Chris Angelico <rosuav@gmail.com> Wrote in message:
> On Mon, Nov 10, 2014 at 10:31 AM, Chris Angelico <rosuav@gmail.com> wrote:
>> So the semantics should be: If NameError would be raised (not
>> including UnboundLocalError, which still represents an error), attempt
>> to import the absent name. If successful, continue as if it had
>> already been done. If ImportError is raised, suppress it and let the
>> original NameError happen.
> 
> No bites? I'd have thought there'd be a few crazy ideas thrown out in
> answer to this.
> 
> What if it's worded as a feature for interactive Python? Save you the
> trouble of explicitly importing modules, by auto-importing them in
> response to usage. In theory, it's as simple as adding __missing__ to
> globals(), but I don't know of a way to do that for the main module.
> 
> ChrisA
> 

I gave it a short whirl, just trying to make __missing__ work.

The type of globals () is a dict. I was able to add a
 __missing__:myfunct to the instance but in order to work, the
 __missing__ must be added as a class attribute,  a method. And
 dict, being implemented in C, doesn't let you add class
 attributes. Presumably the C code does the equivalent of
 slots.

So the next thing to try would be to try to force the module
 dictionary to be a userdict without slots. Then we could add the
 necessary method. But that would be changing the python source. I
 wasn't sure that was within the challenge constraints.

-- 
DaveA

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