python - 获取下一个枚举器常量/属性

Question

假设我有一个枚举器，是否有可能获得后面的属性？因此，如果我有 today=Days.Sunday，我是否能够执行类似 tomorrow=today.next() 的操作？

例子:

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

我知道我可以使用元组(如下所示)来执行类似 tomorrow=today[1] 的操作，但我希望有一些内置的或更优雅的东西。

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

Answer 1

当然。

只需将所需的功能添加到您的 Days 类中:

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]

并在使用中:

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

---

虽然上面的内容可能更容易理解，但可以通过向每个成员添加一个 next 属性(和 previous 当我们这样做的时候)。

class Days(Enum):
    #
    Sunday = 'S'
    Monday = 'M'
    Tuesday = 'T'
    Wednesday = 'W'
    Thursday = 'Th'
    Friday = 'F'
    Saturday = 'Sa'
    #
    def __init__(self, value):
        if len(self.__class__):
            # make links
            all = list(self.__class__)
            first, previous = all[0], all[-1]
            previous.next = self
            self.previous = previous
            self.next = first

并在使用中:

>>> Days.Tuesday.next
<Days.Wednesday: 'W'>

>>> Days.Tuesday.previous
<Days.Monday: 'M'>

>>> Days.Saturday.next
<Days.Sunday: 'S'>

>>> Days.Saturday.previous
<Days.Friday: 'F'>

NB 使用属性的这个方法意味着我们不再需要 next/previous 之后的 () >.