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

[Steven D'Aprano]

On 25/06/13 03:58, Andrew McNabb wrote:
> I'm not even sure I like it, but many of the responses have denied the
> existence of the use case rather than criticizing the solution.

I haven't seen anyone deny that it is possible to write code like

spam(ham=ham, eggs=eggs, toast=toast)

What I've seen is people deny that it happens *often enough* to deserve 
dedicated syntax to "fix" it. (I use scare quotes here because I don't 
actually think that repeating the name that way is a problem that needs 
fixing.)

People have criticized the solution, for its lack of explicitness, for 
being focused on such a narrow special case, for its (subjective) 
ugliness, and for its fragility. Refactoring a variable name shouldn't 
require you to change the way you pass it to a function, but with this 
proposal, it does. If you refactor the name "ham" to "spam" in

func(=ham, eggs=SCRAMBLED, toast=None, coffee='white')

you also need to change the implicit keyword syntax back to ordinary 
explicit keyword syntax, or it will break. (Worse than breaking, if func 
happens to have a parameter "spam" as well, it will silently do the 
wrong thing.) That's a "feature smell", like a code smell but for 
features. I cannot think of any other feature, in any other language, 
where changing a variable's name requires you to change the syntax you 
can use on it.

The OP seems to believe that the existence of an occasional function 
call with a spam=spam parameter is a major factor in discouraging the 
use of keyword arguments everywhere. I do not believe this is the case, 
but even if it were, I say, oh well. We shouldn't want keyword arguments 
*everywhere*, but only where they add clarity rather than mere 
verbosity.


-- 
Steven