[Python-ideas] Unpack of sequences

[Steven D'Aprano]

On 30/08/12 02:10, Mike Graham wrote:
> On Wed, Aug 29, 2012 at 11:45 AM, Masklinn<masklinn at masklinn.net>  wrote:
>> On 2012-08-29, at 17:03 , Guido van Rossum wrote:
>>>
>>> Also of course assignment has no equivalent to keyword parameters
>>
>> I've always thought it would be a rather neat way to unpack
>> dictionaries, instead of doing it by hand or abusing `itemgetter` to get
>> values in a known order.
>
> Do you have a suggestion of a nice syntax for a thing to unpack
> mappings (or to unpack things by attributes)?


a, b, x, y = **mapping

could be equivalent to:

a, b, x, y = mapping['a'], mapping['b'], mapping['x'], mapping['y']


I don't have good syntax for the attribute equivalent, but I do have
bad syntax for it:

a, b, x, y = **.obj

# like a, b, x, y = obj.a, obj.b, obj.x, obj.y


Or you could use wrap your object in a helper class:

class AttrGetter:
     def __init__(self, obj):
         self.obj = obj
     def __getitem__(self, key):
         return getattr(self.obj, key)

a, b, x, y = **AttrGetter(obj)



-- 
Steven