Convert enum to int in python

Question

I have an enum Nationality:

class Nationality:
        Poland='PL'
        Germany='DE'
        France='FR'

How can I convert this some enum to int in this or similar way:

position_of_enum = int(Nationality.Poland)  # here I want to get 0

I know that I can do it if I had code by:

counter=0
for member in dir(Nationality):
    if getattr(Nationality, member) == code:
        lookFor = member
        counter += 1
return counter

but I don't have, and this way looks too big for python. I'm sure that there is something much simpler .

A class is not an enum. Therefor you can't compare.

Bite code
– Bite code

2011-05-19 15:01:38 +00:00
Commented May 19, 2011 at 15:01 — Bite code
– Bite code, Commented May 19, 2011 at 15:01

David K. · Accepted Answer · 2020-09-16 21:25:48Z

160

Please use IntEnum

from enum import IntEnum

class loggertype(IntEnum):
    Info = 0
    Warning = 1
    Error = 2
    Fatal = 3

int(loggertype.Info)
0

edited Sep 16, 2020 at 21:25

David K.

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answered Apr 3, 2018 at 9:37

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3 Comments

Paulie Over a year ago

Please explain your answer.

ac3d912 Over a year ago

As of Python 3.4, this is the "more correct" answer (or, the guy who created the library, Ethan Furman's answer below).

learning2learn Over a year ago

In the above example you could also import auto, then initialize Warning, Error, Fatal, to auto().

Ethan Furman · Accepted Answer · 2017-04-07 18:15:20Z

45

Using either the enum34 backport or aenum¹ you can create a specialized Enum:

# using enum34
from enum import Enum

class Nationality(Enum):

    PL = 0, 'Poland'
    DE = 1, 'Germany'
    FR = 2, 'France'

    def __new__(cls, value, name):
        member = object.__new__(cls)
        member._value_ = value
        member.fullname = name
        return member

    def __int__(self):
        return self.value

and in use:

>>> print(Nationality.PL)
Nationality.PL
>>> print(int(Nationality.PL))
0
>>> print(Nationality.PL.fullname)
'Poland'

The above is more easily written using aenum¹:

# using aenum
from aenum import Enum, MultiValue

class Nationality(Enum):
    _init_ = 'value fullname'
    _settings_ = MultiValue

    PL = 0, 'Poland'
    DE = 1, 'Germany'
    FR = 2, 'France'

    def __int__(self):
        return self.value

which has the added functionality of:

>>> Nationality('Poland')
<Nationality.PL: 0>

¹ Disclosure: I am the author of the Python stdlib Enum, the enum34 backport, and the Advanced Enumeration (aenum) library.

edited Apr 7, 2017 at 18:15

answered Mar 13, 2016 at 0:02

Ethan Furman

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2 Comments

roschach Over a year ago

Great answer but I would like to get some details on what you are doing on __new__ in class Nationality(Enum): is object.__new__ instantiating a new generic object and then setting its attributes? If so why you set _value but then it returns value? Why it does not work if I change from fullname to name?

Ethan Furman Over a year ago

@roschach: Please ask a new question.

Morris · Accepted Answer · 2020-10-23 12:38:00Z

22

from enum import Enum

class Phone(Enum):
    APPLE = 1 #do not write comma (,)
    ANDROID = 2

#as int:
Phone.APPLE.value

Need to access tuple by index if using commas:

class Phone(Enum):
    APPLE = 1, # note: there is comma (,)
    ANDROID = 2,

#as int:
Phone.APPLE.value[0]

edited Oct 23, 2020 at 12:38

answered Oct 23, 2020 at 10:33

Morris

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Comments

per1234 · Accepted Answer · 2018-06-15 16:47:57Z

14

There are better (and more "Pythonic") ways of doing what you want.

Either use a tuple (or list if it needs to be modified), where the order will be preserved:

code_lookup = ('PL', 'DE', 'FR')
return code_lookup.index('PL')

Or use a dictionary along the lines of:

code_lookup = {'PL':0, 'FR':2, 'DE':3}
return code_lookup['PL']

The latter is preferable, in my opinion, as it's more readable and explicit.

A namedtuple might also be useful, in your specific case, though it's probably overkill:

import collections
Nationalities = collections.namedtuple('Nationalities', 
                                       ['Poland', 'France', 'Germany'])
nat = Nationalities('PL', 'FR', 'DE')
print nat.Poland
print nat.index(nat.Germany)

edited Jun 15, 2018 at 16:47

per1234

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answered May 19, 2011 at 15:07

Joe Kington

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2 Comments

user278618 Over a year ago

you miss names of nationality. I must have them

Joe Kington Over a year ago

@user278618 - I left them out for brevity. The idea was that you'd use a lookup table of some sort somewhere in your Nationality class. You could just as easily substitute in your class attributes, instead of strings.

andbmme · Accepted Answer · 2021-11-25 10:36:32Z

9

One straightforward way to achieve this:

from enum import Enum

class Nationality(Enum):
    Poland= 1, 'PL'
    Germany= 2, 'DE'
    France= 3, 'FR'

    def __int__(self):
        return self.value[0]

    def __str__(self):
        return self.value[1]

# Example use
if __name__ == "__main__":
    print(int(Nationality.Poland))
    print(Nationality.Poland)
    print(int(Nationality.Poland) == 1)

Output:

>>> 1
>>> PL
>>> True

Explanation: You can create your enum with the desired numeration and string representation as you wish and you get the desired functionality by overwriting the respective __int__ and __str__ methods. To my knowledge, this does not break any contracts of enum and I prefer to keep functionality encapsulated in their respective classes.

edited Nov 25, 2021 at 10:36

answered Nov 24, 2021 at 18:23

andbmme

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Comments

andrewdski · Accepted Answer · 2011-05-19 15:06:36Z

7

Why don't you just define the values as numbers instead of strings:

class Nationality:
    POLAND = 0
    GERMANY = 1
    FRANCE = 2

If you need to access the two-letter names, you can simply provide a table that maps them. (Or a dictionary that maps the other way, etc.)

answered May 19, 2011 at 15:06

andrewdski

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1 Comment

Michael Dorner Over a year ago

Don't do that because you can change it after definition without any sanity checks: Nationality.GERMANY = 0. This doesn't work in enum, it is WORM (en.wikipedia.org/wiki/Write_once_read_many). The same goes with dicts. Enum is the right choice. :)

blubb · Accepted Answer · 2011-05-19 15:10:08Z

5

You can't. Python does not store the order of class elements and dir() will return them in any order.

Seeing from your comment that you really do require a mapping from strings to integers, you should in fact do exactly that:

code_lookup = {
    'PL': ("Poland", 0), 
    'DE': ("Germany", 1), 
    'FR': ("France", 2), 
    ... 
}

edited May 19, 2011 at 15:10

answered May 19, 2011 at 15:00

blubb

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1 Comment

user278618 Over a year ago

I'm using this enum to set value of select which is at few sites with different css and language, and only value property is at each site the same. From this select I must select nationality, and values of options are 0,1,2. I use this casting in c#, so this is from I took this idea.

janislaw · Accepted Answer · 2011-05-19 15:18:06Z

4

I have seen something like:

PL, FR, DE = range(3)

Wrap it in a class and viola, you have a namespace for the enumeration.

answered May 19, 2011 at 15:18

janislaw

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Comments

Andrzej Piasecki · Accepted Answer · 2020-03-19 08:08:11Z

3

from enum import Enum

class Nationality(Enum):
    Poland = 'PL'
    Germany = 'DE'
    France = 'FR'

    @classmethod
    def get_index(cls, type):
        return list(cls).index(type)

and then:

Nationality.get_index(Nationality.Poland)
0

answered Mar 19, 2020 at 8:08

Andrzej Piasecki

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Comments

AboSari · Accepted Answer · 2022-07-15 03:50:56Z

2

class Nationality(Enum):
    Poland = 'PL'
    Germany = 'DE'
    France = 'FR'

    @property
    def ordinal(self):
        return list(self.__class__).index(self)

    @classmethod
    def get(cls, index):
        return list(cls)[index]

and then:

>>> Nationality.Poland.ordinal
0

also

>>> Nationality.get(2)
Nationality.France

answered Jul 15, 2022 at 3:50

AboSari

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3 Comments

rachwa Over a year ago

Please don't post only code as answer, but also provide an explanation what your code does and how it solves the problem of the question. Answers with an explanation are usually more helpful and of better quality, and are more likely to attract upvotes.

David Lotts Over a year ago

If you add the def __int__() it will do what the op specifically wanted. right? I think this is best answer. I think it might be undervalued because it uses ordinal instead of int.

David Lotts Over a year ago

If you want to keep going down this awesome goose trail, you could replace your get with __call__ to handle Nationality(2) -> Nationality.France. I think you'd need to call super.__call__() for all the non-int args it handles.

Thinkal VB · Accepted Answer · 2022-09-04 19:57:29Z

0

This method is something I am using

from enum import Enum
ClientType_DICT = {
    "1": 'webapp',
    "2": 'application',
    "3": 'embedded'
}
ClientType_ENUM: Enum = Enum('ClientType_ENUM', ClientType_DICT)
print(int(ClientType_ENUM('webapp').name))

@app.post("/example")
def login(device_type: ClientType_ENUM):
    deviceType = int(device_type.name) # print 1

edited Sep 4, 2022 at 19:57

answered Sep 4, 2022 at 19:48

Thinkal VB

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Comments

David Lotts · Accepted Answer · 2024-06-19 05:56:36Z

0

I would recommend using an enum. Instead of values of integers, use values of named-tuples with the integer as one of the tuple values. You can add any amount of data to your tuple. Add capital city, language, and population! The the enum and namedTuple work very well together:

from enum import Enum
from collections import namedtuple

Nat = namedtuple('Nat', ['id', 'abbr'])

class Nationality(Enum):
    Poland = Nat(0,'PL')
    Germany = Nat(1,'DE')
    France = Nat(2,'FR')

    def __int__(self):
        return self.value.id

    def __str__(self):
        return self.value.abbr

The __int__ and __str__ are really optional, but allow you to use the int() and str() functions to access your id and abbr.

Look at all the functionality you get! The first one is what you wanted.

>>> position_of_enum = int(Nationality.Poland)  # here I want to get 0
>>> abbr_of_enum = str(Nationality.Poland)  #  "PL"
>>> print(position_of_enum,abbr_of_enum)
0 PL

>>> home=Nationality.France
>>> print(home)
FR

>>> print(int(home)) 
2

>>> print(home.name)
France

>>> print(home.value)
Nat(id=2, abbr='FR')

>>> print(home.value.id)
2

>>> print(home.value.abbr)
FR

edited Jun 19, 2024 at 5:56

answered Jun 19, 2024 at 5:45

David Lotts

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1 Comment

David Lotts Over a year ago

This is just like @ndbmme's answer except they used regular tuples. Where they have self.value[0], I have the equivalent self.value.id.

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