Get next enumerator constant/property

问题

Lets's say I have an enumerator, is it possible to get the property that follows? So if I had today=Days.Sunday would I be able to do something like tomorrow=today.next()?

example:

class Days(Enum):
     Sunday = 'S'
     Monday = 'M'
     ...
     Saturday = 'Sa'

I know I could use tuples (like below) to do something like tomorrow=today[1], but I was hoping there was something built in or more elegant.

class Days(Enum):
     Sunday = ('S','Monday')
     Monday = ('M','Tuesday')
     ...
     Saturday = ('Sa','Sunday')

回答1:

Absolutely.

Just add the desired functionality to your Days class:

class Days(Enum):

    Sunday = 'S'
    Monday = 'M'
    Tuesday = 'T'
    Wednesday = 'W'
    Thursday = 'Th'
    Friday = 'F'
    Saturday = 'Sa'

    def next(self):
        cls = self.__class__
        members = list(cls)
        index = members.index(self) + 1
        if index >= len(members):
            index = 0
        return members[index]

and is use:

today = Days.Wednesday
print(today.next())
# Days.Thursday

回答2:

You can create a dictionary to lookup the next day like so:

In [10]: class Days(Enum):
    Sun = 'Su'
    Mon = 'M'
    Tue = 'Tu'
    Wed = 'W'
    Thu = 'Th'
    Fri = 'F'
    Sat = 'Sa'

In [11]: days = list(Days)

In [12]: nxt = dict((day, days[(i+1) % len(days)]) for i, day in enumerate(days))

Quick test:

In [13]: nxt[Days.Tue]
Out[13]: <Days.Wed: 'W'>

In [14]: nxt[Days.Sat]
Out[14]: <Days.Sun: 'Su'>

回答3:

#ENUM CLASS

#colors
import enum

class Color(enum.Enum):
    turquoise = 1
    indigo = 2
    magenta = 3
    cyan = 4
    teal = 5
    azure = 6
    rose = 7
    amber = 8
    vermillon = 9
    plum = 10
    russet = 11
    slate = 12

    def __iter__(self):
        self.idx_current = self.value
        return self

    def __next__(self):
        if (self.idx_current > 12):
            return None

        self.idx_current = self.idx_current + 1
        return Color (self.idx_current - 1)

#CLIENT CODE
    #iterate colors starting from cyan
    it = iter (Color.cyan)
    while True:
        #print (v.get_id())
        c = next (it)
        if c is None:
            break
        print(c)

#OUTPUT
Color.cyan
Color.teal
Color.azure
Color.rose
Color.amber
Color.vermillon
Color.plum
Color.russet
Color.slate

来源：https://stackoverflow.com/questions/26577621/get-next-enumerator-constant-property