[Python-ideas] Quick idea: defining variables from functions that take the variable name

[Sjoerd Job Postmus]

> On 1 Jun 2016, at 18:14, Steven D'Aprano <steve at pearwood.info> wrote:
> 
> On Tue, May 31, 2016 at 01:09:05PM -0300, Alan Cristhian wrote:
>>> The fundamental use-case here is "any object that needs to know its own
>>> name". Most objects need more than just a name.
>> 
>> A more general solution could be:
>> 
>>    def x, y, z as <expression>
>> 
>> Where <expression> should return a callable that accept only one argument.
> 
> You should consider how your suggestion will work with the existing 
> use-cases already shown.
> 
> We've got two dead-simple use-cases to consider. If this proposal makes 
> those use-cases harder than the status quo, then this proposal is dead 
> in the water. Nobody is going to use it.
> 
> 
> # Status quo.
> T = Typevar('T')
> x = sympy.Symbol('x')
> 
> # My proposal.
> T -> Typevar()
> x -> sympy.Symbol()
> 
> 
> # Your proposal.
> def T as (lambda: Typevar)()
> def x as (lambda: sympy.Symbol)()

Correct me if I'm wrong, but wouldn't it be

    def T as Typevar

Unless you're being (rightfully) pedantic about "must return" implying that the expression will be called as a 0-argument function and that result called with the name?

> 
> You specify that the expression on the right must return a function that 
> takes one variable, so you cannot use Typevar or Symbol directly. You 
> have to call a function that returns the function you actually want.
> 
> Syntactic sugar is supposed to make things easier, not harder.
> 
> 
> 
> -- 
> Steve
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