[Python-ideas] Short form for keyword arguments and dicts

[MRAB]

On 29/06/2013 17:56, Steven D'Aprano wrote:
> On 30/06/13 02:20, Joshua Landau wrote:
>
>> We*do*  have a way of extracting a submap from a dict.
>
> Er, not really. Here's a dict: {}
>
> What you talk about is extracting named attributes from a module or package namespace. That modules happen to use a dict as the storage mechanism is neither here nor there. I can do this:
>
> class NoDict(object):
>       __slots__ = ['eggs']
>
> fake_module = NoDict()
> fake_module.eggs = 42
> assert not hasattr(fake_module, '__dict__')
>
> sys.modules['spam'] = fake_module
>
> from spam import eggs
>
>
> and it all just works. But I'm no closer to extracting a subdict from a dict.
>
>
>> We*already*  have a way of writing
>>
>>      foo = foo
>>
>> across scopes, as we want to do here.
>
> We sure do. And that's by just explicitly writing foo=foo. This is not a problem that needs solving. I'm kind of astonished that so many words have been spilled on a non-problem just to save a few characters for such a special case.
>
>
>> This problem*has*  been solved before, and it looks like:
>>
>>      from module import these, are, in, the, submap
>
> As I show above, this is about named attribute access, not dicts. And as you admit below, it doesn't lead to good syntax for extracting a subdict:
>
>
>> I haven't been able to find a really good syntax from this, but something like:
>>
>> 1) foo(a, b, **(key1, key2 from locals()))
>>
>> 2) {**(key1, key2 from locals())}
>>
>> 3) import key1, key2 from {"key1": 123, "key2": 345}
>>
>> etc.
>>
You could just add a method to dict:

foo(a, b, **locals().subdict(["key1", "key2"]))

>> And, á mon avis, it's a hell of a lot better than previous proposals
>> for (1) and (2) from this thread, and (3) from other threads.
>>
>> Again, not a proposal per se but a revelation.
>
>
>