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

[Steven D'Aprano]

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.
>
> 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.



-- 
Steven