Enum is great! Okay, okay, my opinion might be biased. ;)
There is one area where Enum is not great -- for a bunch of unrelated values. What would be nice is if we had something
similar to Enum for the
- repr()
- constantness of the name/value relationship
While I was looking in the stdlib for an example, I came across sre_constants, which was chock full of constants -- and
it even has a minimal version of what I'm proposing:
class _NamedIntConstant(int):
def __new__(cls, value, name):
self = super(_NamedIntConstant, cls).__new__(cls, value)
self.name = name
return self
def __repr__(self):
return self.name
My proposal, compared/contrasted with Enum:
like Enum, NamedValues will be in collections (a class) that will keep those names from being deleted or rebound to
other values
like Enum, NamedValues will have `value` and `name` attributes, and also a
`type` attribute
like Enum, NamedValues are attributes of their containing class
like Enum, iterating over the containing class will yield the names/values
defined
like Enum, a class of NamedValues do not have to all be the same data type
unless one is mixed in
like Enum, a particular name/value combination is a singleton
unlike Enum, duplicates are allowed
unlike Enum, new values can be added after class definition
unlike Enum, a NamedValue can always be used as-is, even if no data type has been mixed in -- in other words, there is
no functional difference between MyIntConstants(int, NamedValue) and MyConstants(NamedValue).
If sre_constants was using a new data type, it should probably be IntEnum instead. But sre_parse is a good candidate
for NamedValues:
class K(NamedValues):
DIGITS = frozenset("0123456789")
OCTDIGITS = frozenset("01234567")
HEXDIGITS = frozenset("0123456789abcdefABCDEF")
ASCIILETTERS =
frozenset("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
WHITESPACE = frozenset(" \t\n\r\v\f")
_REPEATCODES = frozenset({MIN_REPEAT, MAX_REPEAT})
_UNITCODES = frozenset({ANY, RANGE, IN, LITERAL, NOT_LITERAL, CATEGORY})
and in use:
>>> K.DIGITS
K.DIGITS
>>> K.DIGITS.name
'DIGITS'
>>> K.DIGITS.value
frozenset("0123456789")
Thoughts?
--
~Ethan~
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