[Python-ideas] Let's be more orderly!

[Ethan Furman]

On 05/15/2013 09:27 AM, Amaury Forgeot d'Arc wrote:
> 2013/5/15 Don Spaulding <donspauldingii at gmail.com <mailto:donspauldingii at gmail.com>>
>
>     Even if the only ordering change that was made was to magically give OrderedDict.__init__ its **kwargs in order, it
>     would clean up these instances, which I initially referred to as literals.
>
>     foo = OrderedDict(
>          b=1,
>          a=2
>     )
>
>
> Since PEP3115, classes can __prepare__ a custom dict:
>
> from collections import OrderedDict
> class OrderedDictBuilder(type):
>      @classmethod
>      def __prepare__(metacls, name, bases):
>          return OrderedDict()
>      def __new__(cls, name, bases, classdict):
>          del classdict['__module__']  # ugh
>          return classdict
>
> Then we can (ab)use the Class syntax to preserve the order!
>
> class foo(metaclass=OrderedDictBuilder):
>      b = 1
>      a = 2
>
> assert repr(foo) == "OrderedDict([('b', 1), ('a', 2)])"
>
> There is probably a way to get rid of the "metaclass=" part.
> I'm not sure to like it, though.

class OrderedDict(metaclass=OrderedDictBuilder):
     pass

class foo(OrderedDict):
     b = 1
     a = 2

--
~Ethan~