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

[Amaury Forgeot d'Arc]

2013/5/15 Don Spaulding <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.

-- 
Amaury Forgeot d'Arc
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