[Python-ideas] namedtuple literals [Was: RE a new namedtuple]

[MRAB]

On 2017-07-23 17:08, Todd wrote:
> 
> On Jul 20, 2017 1:13 AM, "David Mertz" <mertz at gnosis.cx 
> <mailto:mertz at gnosis.cx>> wrote:
> 
>     I'm concerned in the proposal about losing access to type
>     information (i.e. name) in this proposal.  For example, I might
>     write some code like this now:
> 
>      >>> from collections import namedtuple
>      >>> Car = namedtuple("Car", "cost hp weight")
>      >>> Motorcycle = namedtuple("Motorcycle", "cost hp weight")
>      >>> smart = Car(18_900, 89, 949)
>      >>> harley = Motorcyle(18_900, 89, 949)
>      >>> if smart==harley and type(smart)==type(harley):
>     ...     print("These are identical vehicles")
> 
>     The proposal to define this as:
> 
>      >>> smart = (cost=18_900, hp=89, weight=949)
>      >>> harley = (cost=18_900, hp=89, weight=949)
> 
>     Doesn't seem to leave any way to distinguish the objects of
>     different types that happen to have the same fields.  Comparing
>     `smart._fields==harley._fields` doesn't help here, nor does any type
>     constructed solely from the fields.
> 
> 
> What about making a syntax to declare a type? The ones that come to mind are
> 
>      name = (x=, y=)
> 
> Or
> 
>      name = (x=pass, y=pass)
> 
> They may not be clear enough, though.
> 
Guido has already declared that he doesn't like those bare forms, so 
it'll probably be something like ntuple(...).