There are currently a few locations in the stdlib, such as http and socket, that are now using Enums to replace constants; those names are all upper-case -- those aren't the names I am speaking of.
The names I am speaking of are those in brand-new enumerations where we have full control.
As an example:
class FederalHoliday(AutoNumberEnum): NewYear = "First day of the year.", 'absolute', JANUARY, 1 MartinLutherKingJr = "Birth of Civil Rights leader.", 'relative', JANUARY, MONDAY, 3 President = "Birth of George Washington", 'relative', FEBRUARY, MONDAY, 3 Memorial = "Memory of fallen soldiers", 'relative', MAY, MONDAY, 5 Independence = "Declaration of Independence", 'absolute', JULY, 4 Labor = "American Labor Movement", 'relative', SEPTEMBER, MONDAY, 1 Columbus = "Americas discovered", 'relative', OCTOBER, MONDAY, 2 Veterans = "Recognition of Armed Forces service", 'relative', NOVEMBER, 11, 1 Thanksgiving = "Day of Thanks", 'relative', NOVEMBER, THURSDAY, 4 Christmas = "Birth of Jesus Christ", 'absolute', DECEMBER, 25
def __init__(self, doc, type, month, day, occurance=None): self.__doc__ = doc self.type = type self.month = month self.day = day self.occurance = occurance
def date(self, year): """ returns the observed date of the holiday for `year` """" ...
@classmethod def next_business_day(cls, date, days=1): """ Return the next `days` business day from date. """ ... @classmethod def count_business_days(cls, date1, date2): """ Return the number of business days between 'date1' and 'date2'. """ ... @classmethod def year(cls, year): """ Return a list of the actual FederalHoliday dates for `year`. """ ... Take the name "NewYear": if it had been a global constant I would have named it "NEWYEAR"; if it had been a normal class attribute I would have named it "new_year"; however, being an Enum member, it is neither of those things.
<context switch> I've written some custom data types as part of my dbf package, and a few of them have instances that are singletons that are created in the global (okay, module) namespace, and for them I followed Python's lead in naming singletons: Python has used Title Case in such things as None, True, and False, so I followed suit and named mine -- Null, NullDate, NullTime, NullDateTime, etc. </context switch>
Given my past history with using and creating singleton objects, I followed suit when creating my own Enum classes.
I was recently queried about my apparent break with PEP 8 for naming Enum members, to which I replied:
Considering the strange beast that an Enum is, there is not much precedent for it anywhere.
Enum is a class
but it is a container
and can be iterated over
and it has a length (which can be zero)
but it's always True in a boolean sense
Enum members are instances of the Enum class
but are pre-created
and new ones cannot be created
but are available as attributes on the class
Given all that I have been using Title case (or CamelCase) to name the members as it helps distinguish an Enum member from an ordinary attribute (which Enum classes can also have).
I forgot to include in that reply that I think CamelCase also helps to emphasize the special singleton nature of Enum members.
My question for the community: Your thoughts/opinions of my reasoning, and if you don't agree then which casing choice would you recommend and use, and why? (Reminder: this question does not include Enums whose names are replacements for existing constants and so the names cannot be changed.)