[Python-ideas] Assignment decorators (Re: The Descriptor Protocol...)

Tue Mar 8 02:24:49 CET 2011

On 03/07/2011 08:08 PM, Chris Kaynor wrote:
> You seemed to have missed the example of:
>> lhs = @dec1 123
>> which would produce
>> dec1(classobject, 'lhs', 123)
>> correct?

No, that was deliberately not part of my proposal. My thinking: most of 
the time, this will be used in class scope for creating objects that 
have their own reasonable default values. Why force people to type in a 
default value that 99% of the time you don't care about? Allowing you 
to override this default value would be done by making the decorator 
callable and return a callable, like
 lhs = @dec1(123)
Also, I thought the "@dec1 123" style just looked too weird. I admit it 
isn't that much weirder than what I already proposed.
However, if there are great uses for assignment decorators outside class 
scope, perhaps we need this original rhs. Other folks have pointed 
out--what does something like this mean?
 c = Class()
 c.member = @dec
Does dec get 'c.member'? Is this useful for anything? Shall we narrow 
the use of assignment decorators to just class scope?
On 03/07/2011 08:08 PM, Joao S. O. Bueno wrote:
> What you are calling "classobject" simply don't exist at this stage
> wen creating a new class.

Toldja it probably wasn't a good idea!
> This is Python, where function calls has "(" .

I'm not sure if this is part of a default signature or a rejoinder to 
me. If the latter, let me point out that class/function decorators are 
already function calls without parentheses; it seems natural enough that 
assignment decorators would similarly lack them.
/larry/