What's the common practice for enums in Python?

Question

How can I implement an enumeration type (spelled enum in some languages) in Python? What is the common practice to get this functionality?

Asked By: Joan Venge

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Source

Answer 1

I’ve seen this pattern several times:

>>> class Enumeration(object):
        def __init__(self, names):  # or *names, with no .split()
            for number, name in enumerate(names.split()):
                setattr(self, name, number)

>>> foo = Enumeration("bar baz quux")
>>> foo.quux
2

You can also just use class members, though you’ll have to supply your own numbering:

>>> class Foo(object):
        bar  = 0
        baz  = 1
        quux = 2

>>> Foo.quux
2

If you’re looking for something more robust (sparse values, enum-specific exception, etc.), try this recipe.

Answered By: Ben Blank

Answer 2

I have no idea why Enums are not support natively by Python.
The best way I’ve found to emulate them is by overridding _ str _ and _ eq _ so you can compare them and when you use print() you get the string instead of the numerical value.

class enumSeason():
    Spring = 0
    Summer = 1
    Fall = 2
    Winter = 3
    def __init__(self, Type):
        self.value = Type
    def __str__(self):
        if self.value == enumSeason.Spring:
            return 'Spring'
        if self.value == enumSeason.Summer:
            return 'Summer'
        if self.value == enumSeason.Fall:
            return 'Fall'
        if self.value == enumSeason.Winter:
            return 'Winter'
    def __eq__(self,y):
       return self.value==y.value

Usage:

>>> s = enumSeason(enumSeason.Spring)

>>> print(s)

Spring

Answered By: Spell

Answer 3

class Materials:
    Shaded, Shiny, Transparent, Matte = range(4)

>>> print Materials.Matte
3

Answered By: Van Gale

Answer 4

You could probably use an inheritance structure although the more I played with this the dirtier I felt.

class AnimalEnum:
  @classmethod
  def verify(cls, other):
    return issubclass(other.__class__, cls)


class Dog(AnimalEnum):
  pass

def do_something(thing_that_should_be_an_enum):
  if not AnimalEnum.verify(thing_that_should_be_an_enum):
    raise OhGodWhy

Answered By: Trey Stout

What's the common practice for enums in Python?

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