Enum class in python

This question already has an answer here:

How can I represent an 'Enum' in Python? 43 answers

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I would recommend to achieve you goal using metaclasses, in order to minimise the client code. So first of all checkout the below metaclass:

class EnumMeta(type):
    def __getattribute__(self, name):
        actual_value = super(EnumMeta, self).__getattribute__(name)
        if isinstance(actual_value, self):
            return actual_value
        else:
            new_value = self(actual_value)
            super(EnumMeta, self).__setattr__(name, new_value)
            return new_value

It simply overrides the __getattribute__ and returns an instance of the child class using the attributes value as the constructor argument. Also it updates the original value, in order not to create a new instance every time, and besides to make equality check using the reference of the object

Then define an Enum class like this:

class Enum(object):
    __metaclass__ = EnumMeta

    def __init__(self, value):
        super(Enum, self).__init__()

        self.value = value[0]
        self.repr = value[1]

    def __repr__(self):
        return str(self.repr)

This base class implements equals ( == ) operator, to compare using the int value, and __repr__ method, to return the string representation of your enum. So here you go:

class Operation(Enum):
    START = (0, "start")
    STOP = (1, "stop")

>>> Operation.START == Operation.START
True
>>> Operation.START is Operation.START
True
>>> Operation.START == Operation.STOP
False
>>> Operation.START
"start"
>>> repr(Operation.STOP)
"stop"

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Enum s in Python are either:

built-in as of Python 3.4

available as a backport for Python 3.3 down to Python 2.4

available in an enhanced library which also includes a class-based NamedTuple and a Constant class

Using that your code would look like:

from aenum import IntEnum   # or from enum import IntEnum

class Operation(IntEnum):
    START = 0
    STOP = 1

>>> Operation.START
<Operation.START: 0>

>>> Operation['START']
<Operation.START: 0>

>>> Operation(0)
<Operation.START: 0>

>>> Operation.STOP is Operation.STOP
True

>>> list(Operation)
[<Operation.START: 0>, <Operation.STOP: 1>]

>>> Operation.STOP.name
'STOP'

>>> Operation.STOP.value
1

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