[Python-Dev] [Python-checkins] peps: Pre-alpha draft for PEP 435 (enum). The name is not important at the moment, as
ethan at stoneleaf.us
Tue Feb 26 22:55:57 CET 2013
On 02/26/2013 12:52 PM, Tim Delaney wrote:
> On 27 February 2013 01:50, Terry Reedy <tjreedy at udel.edu <mailto:tjreedy at udel.edu>> wrote:
>> We should NOT knowingly re-introduce the same problem again! If color and animal are isolated from each other, they
>> should each be isolated from everything, including int.
> FWIW the only reason I made my enums int-based (and comparable with ints) was because I read somewhere that Guido had
> said that any stdlib enum would have to be an int subclass.
I recall that as well.
> I have no problems with having int-like enums that:
> 1. Are not int subclasses;
> 2. Do not compare equal with ints unless explicitly converted.
> I do think an int-like enum should implement both __int__ and __index__.
I think it will take more than one type of Enum to handle the myriad needs.
1) Default enumeration: valueless, unordered:
eggs = 'from a chicken'
ham = 'from a pig'
spam = 'from a ... um ... '
2) non-valued, yet ordered:
sunday = 'last day of weekend'
monday = 'is it the 13th??'
tuesday = 'not as bad as monday'
wednesday = 'halfway through!'
thursday = 'almost there...'
friday = 'thank goodness'
saturday = 'sleeping in!'
3) bitmask: sub-classes int, but not directly interactable (except for shifts)
binary = 'no unicode translation'
nullable = 'can store None'
system = 'internal use only'
4) named string (based on str, basically a named constant)
top = north = 'top'
bottom = south = 'bottom'
left = west = 'left'
right = east = 'right'
5) named integer (based on int, basically a named constant)
name = 0
address = 1
city = 2
state = 3
zip = 4
In the first three examples the data in quotes is the doc string; in examples 4 and 5 the RHS is the actual value
assigned. For that matter, 4 and 5 could be compacted into a NamedValue class, allowing whatever type is needed (since
set membership is not restricted anyway):
top = 'top', 'top, or north, edge'
bottom = 'bottom', 'bottom, or south, edge'
pi = 3.14159, "circle's circumference divided by it's radius"
lucky = 7, 'come on, 7!'
unlucky = 2, 'snake eyes!'
That would get us to three enum classes and one namedvalue class, and should cover 99% of the use cases out there.
Does anyone still reading this thread have a use case not covered by the above?
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