On 29/04/13 10:29, Ethan Furman wrote:
On 04/28/2013 04:37 PM, Steven D'Aprano wrote:
On Sun, Apr 28, 2013 at 12:32 PM, Ethan Furman <ethan@stoneleaf.us> wrote:
- should an enum item be selectable via __call__ instead of __getitem__ (i.e. Seasons(3) is AUTUMN)
Does anyone know why this is even an issue? Is this pure bike-shedding over the API, or are there technical reasons for choosing one over the other?
This is an issue because currently every other type* in Python creates (or selects ;) its instances via the call syntax:
- bool(1) # True - int('11') # 11 - str(var) # whatever var had in it, now as a str
I think that's a red herring, because you're comparing the use of the object constructor with look-up by name. Seasons[3] should not be considered as constructing an instance from argument 3, but a reverse lookup from raw value to enum value. Hence the use of __getitem__ rather than __call__.
But one of the latest changes to flufl.enum was to take out the call syntax, and have only getitem syntax
- Season('AUTUMN') # raises an exception - Season['AUTUMN'] # Season.AUTUMN
I'm not sure whether flufl.enums support creating additional instances after the event, but if it did, I would expect that I could say Season('WET') to get a new instance. I am indifferent to whether or not Season('AUTUMN') should return the existing AUTUMN enum value. I think that I lean very slightly to these rules: - Season(x) constructs new instances. If x is already a Season enum, it returns x; otherwise if x is a value already used for a Season enum, it raises. - Season[x] looks up existing instances, and raises if x is not already a Season value. but only very slightly.
Not only is this inconsistent with the rest of Python*, but it's going to be a PITA for data storage/retrieval:
datastore = dbf.Table('storage.dbf', 'event_name C(50); date D; season SEASON')
def retrieve_record(...): result = [] for field_type, field_data in record: result.append(field_type(field_data))
Instead of having field_type be Season, couldn't you make it Season.__getitem__ ? -- Steven