[Python-Dev] PEP 435 -- Adding an Enum type to the Python standard library
barry at python.org
Thu Apr 25 23:39:45 CEST 2013
On Apr 25, 2013, at 02:25 PM, Eli Bendersky wrote:
>I think it's important to stress what this syntax is actually going to be
>used for. No one (I hope) is actually going to write Animals(1) or
>Animals. They will write Animals.ant - this is what enums are for in the
>first place! The way I see it, this syntax is for enabling *programmatic
>access* - if you pull the value from a DB and want to convert it to an
>actual enum value, etc. So do we really need to have two syntaxes for this?
Excellent point, and no, we don't :).
>The call syntax already has other uses, and it's weird because:
>Enum(....) -> Creates new enums
>Animals(....) --> accesses values ?! This is contradictory
>Animals[...] to serve as a by-value lookup makes sense, though.
I think so too. :)
Note that I discovered that the same two-value call syntax on Enum can be used
on the derived classes. It's exactly the same as using subclassing syntax to
extend an existing enum. E.g.
>>> class A(Enum):
... a = 1
... b = 2
... c = 3
>>> class B(A):
... d = 4
... e = 5
>>> B.a is A.a
>>> X = Enum('X', 'a b c')
>>> Y = X('Y', (('d', 4), ('e', 5)))
>>> Y.a is X.a
That's a nice symmetry.
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