[Python-ideas] Let's be more orderly!

[Terry Jan Reedy]

On 5/23/2013 12:36 PM, Haoyi Li wrote:
>  >The question is, how would you _specify_ that option?
>
> This seems like the perfect use case for function annotations, or a
> decorator. I imagine both cases would look rather pretty
>
> def func(**kwargs: ordered):
>      ...

Guido has more or less rejected annotations because checking for an 
anotation would slow down every function call for the benefit of very few.

> @ordered_kwargs
> def func(**kwargs):
>      ...

Returning a function with a custom ordered kwargs .__call__ method would 
not affect normal functions. func.__class__ cannot be changed from 
Python code (non-heap type) but I don't know about from C. In any case, 
the attributes (components) of func could be fed to an okw_function 
(ordered keyword function) class to produce an new object.

The decorator approach immediately fails for a system without the 
decorator. Since it should only be used for funcs that require the 
ordering, I think that would be appropriate.

tjr