Ordering python sets

[Terry Reedy]

Lie Ryan wrote:
> On Sat, 25 Oct 2008 18:20:46 -0400, Terry Reedy wrote:

>>> a = list([1, 2, 3, 4, 5], implementation = 'linkedlist')
>> For this to work, the abstract list would have to know about all
>> implementations of the abstraction.
> 
> /the exact syntax isn't really important/
> /abstract type and implementation separation is the important point/
> 
> Actually, if I want to force it, that syntax could work using the same 
> magic used by event-based systems: registration. 

ABCs have registration method.  The builtin ABCs have appropriate 
builtin classes preregistered.
 >>> import collections as co
 >>> mu = co.MutableSequence
 >>> issubclass(list, mu)
True

I believe user classes that inherit from an ABC are also registered, and 
other can be registered explicitly.

>Although I agree it 
> might be a bit cumbersome to do registration for something like this, but 
> as I've said before, exact syntax is not really important.

Then why do you object to current
   	mylist = linkedlist(data)
and request the harder to write and implement
   	mylist = list(data, implementation = 'linkedlist')
?

tjr