Choices Enum

Python’s Enum with extra powers to play nice with labels and choices fields.

• Free software: BSD license

• Documentation: https://python-choicesenum.readthedocs.io.

Installation

Install choicesenum using pip:

$ pip install choicesenum

Features

• An ChoicesEnum that can be used to create constant groups.

• ChoicesEnum can define labels to be used in choices fields.

• Django fields included: EnumCharField and EnumIntegerField.

• All ChoicesEnum types can be compared against their primitive values directly.

• Support (tested) for Python 2.7, 3.5, 3.6, 3.7 and 3.8.

• Support (tested) for Django 1.9, 1.10, 1.11, 2.0, 2.1, 2.2 and 3.0.

Usage examples

Example with HttpStatuses:

class HttpStatuses(ChoicesEnum):
    OK = 200
    BAD_REQUEST = 400
    UNAUTHORIZED = 401
    FORBIDDEN = 403

Example with Colors:

from choicesenum import ChoicesEnum

class Colors(ChoicesEnum):
    RED = '#f00', 'Vermelho'
    GREEN = '#0f0', 'Verde'
    BLUE = '#00f', 'Azul'

Comparison

All Enum types can be compared against their values:

assert HttpStatuses.OK == 200
assert HttpStatuses.BAD_REQUEST == 400
assert HttpStatuses.UNAUTHORIZED == 401
assert HttpStatuses.FORBIDDEN == 403

status_code = HttpStatuses.OK
assert 200 <= status_code <= 300

assert Colors.RED == '#f00'
assert Colors.GREEN == '#0f0'
assert Colors.BLUE == '#00f'

Label for free

All Enum types have by default a display derived from the enum identifier:

assert HttpStatuses.OK.display == 'Ok'
assert HttpStatuses.BAD_REQUEST.display == 'Bad request'
assert HttpStatuses.UNAUTHORIZED.display == 'Unauthorized'
assert HttpStatuses.FORBIDDEN.display == 'Forbidden'

You can easily define your own custom display for an Enum item using a tuple:

class HttpStatuses(ChoicesEnum):
    OK = 200, 'Everything is fine'
    BAD_REQUEST = 400, 'You did a mistake'
    UNAUTHORIZED = 401, 'I know your IP'
    FORBIDDEN = 403

assert HttpStatuses.OK.display == 'Everything is fine'
assert HttpStatuses.BAD_REQUEST.display == 'You did a mistake'
assert HttpStatuses.UNAUTHORIZED.display == 'I know your IP'
assert HttpStatuses.FORBIDDEN.display == 'Forbidden'

Dynamic properties

For each enum item, a dynamic property is_<enum_item> is generated to allow quick boolean checks:

color = Colors.RED
assert color.is_red
assert not color.is_blue
assert not color.is_green

This feature is usefull to avoid comparing a received enum value against a know enum item.

For example, you can replace code like this:

# status = HttpStatuses.BAD_REQUEST

def check_status(status):
    if status == HttpStatuses.OK:
        print("Ok!")

To this:

def check_status(status):
    if status.is_ok:
        print("Ok!")

Custom methods and properties

You can declare custom properties and methods:

class HttpStatuses(ChoicesEnum):
    OK = 200, 'Everything is fine'
    BAD_REQUEST = 400, 'You did a mistake'
    UNAUTHORIZED = 401, 'I know your IP'
    FORBIDDEN = 403

    @property
    def is_error(self):
        return self >= self.BAD_REQUEST

assert HttpStatuses.OK.is_error is False
assert HttpStatuses.BAD_REQUEST.is_error is True
assert HttpStatuses.UNAUTHORIZED.is_error is True

Iteration

The enum type is iterable:

>>> for color in Colors:
...     print(repr(color))
Color('#f00').RED
Color('#0f0').GREEN
Color('#00f').BLUE

Order is guaranteed only for py3.4+. For fixed order in py2.7, you can implement a magic attribute _order_:

from choicesenum import ChoicesEnum

class Colors(ChoicesEnum):
    _order_ = 'RED GREEN BLUE'

    RED = '#f00', 'Vermelho'
    GREEN = '#0f0', 'Verde'
    BLUE = '#00f', 'Azul'

Choices

Use .choices() method to receive a list of tuples (item, display):

assert list(Colors.choices()) == [
    ('#f00', 'Vermelho'),
    ('#0f0', 'Verde'),
    ('#00f', 'Azul'),
]

Values

Use .values() method to receive a list of the inner values:

assert Colors.values() == ['#f00', '#0f0', '#00f', ]

Options

Even if a ChoicesEnum class is an iterator by itself, you can use .options() to convert the enum items to a list:

assert Colors.options() == [Colors.RED, Colors.GREEN, Colors.BLUE]

A “dict like” get

Use .get(value, default=None) method to receive default if value is not an item of enum:

assert Colors.get(Colors.RED) == Colors.RED
assert Colors.get('#f00') == Colors.RED
assert Colors.get('undefined_color') is None
assert Colors.get('undefined_color', Colors.RED) == Colors.RED

Compatibility

The enum item can be used whenever the value is needed:

assert u'Currrent color is {c} ({c.display})'.format(c=color) ==\
       u'Currrent color is #f00 (Vermelho)'

Even in dicts and sets, as it shares the same hash() from his value:

d = {
    HttpStatuses.OK.value: "using value",
    HttpStatuses.BAD_REQUEST: "using enum",
    401: "from original value",
}
assert d[HttpStatuses.OK] == "using value"
assert d[HttpStatuses.BAD_REQUEST.value] == "using enum"
assert d[HttpStatuses.OK] == d[HttpStatuses.OK.value]
assert d[HttpStatuses.UNAUTHORIZED] == d[401]

There’s also optimistic casting of inner types:

assert int(HttpStatuses.OK) == 200
assert float(HttpStatuses.OK) == 200.0
assert str(HttpStatuses.BAD_REQUEST) == "400"

Check membership:

assert HttpStatuses.OK in HttpStatuses
assert 200 in HttpStatuses
assert 999 not in HttpStatuses

JSON

If you want json serialization, you have at least two options:

1. Patch the default serializer.

2. Write a custom JSONEncoder.

ChoicesEnum comes with a handy patch funtion, you need to add this code to somewhere at the top of everything to automagically add json serialization capabilities:

from choicesenum.patches import patch_json
patch_json()

Note

Eventually __json__ will be added to the stdlib, see https://bugs.python.org/issue27362

Django

Fields

Usage with the custom Django fields:

from django.db import models
from choicesenum.django.fields import EnumCharField

class ColorModel(models.Model):
    color = EnumCharField(
        max_length=100,
        enum=Colors,
        default=Colors.GREEN,
    )

instance = ColorModel()
assert instance.color ==  Colors.GREEN
assert instance.color.is_green is True
assert instance.color.value == Colors.GREEN.value == '#0f0'
assert instance.color.display == Colors.GREEN.display

instance.color = '#f00'
assert instance.color == '#f00'
assert instance.color.value == '#f00'
assert instance.color.display == 'Vermelho'

Is guaranteed that the field value is always a ChoicesEnum item. Pay attention that the field will only accept valid values for the Enum in use, so if your field allow null, your enum should also:

from django.db import models
from choicesenum import ChoicesEnum
from choicesenum.django.fields import EnumIntegerField

class UserStatus(ChoicesEnum):
    UNDEFINED = None
    PENDING = 1
    ACTIVE = 2
    INACTIVE = 3
    DELETED = 4


class User(models.Model):
    status = EnumIntegerField(enum=UserStatus, null=True, )

instance = User()
assert instance.status.is_undefined is True
assert instance.status.value is None
assert instance.status == UserStatus.UNDEFINED
assert instance.status.display == 'Undefined'

# again...
instance.status = None
assert instance.status.is_undefined is True

Graphene

Usage with Graphene Enums:

UserStatusEnum = graphene.Enum.from_enum(UserStatus)

Schematics

Usage with Schematics Enums:

from schematics.models import Model as SchematicModel
from schematics.types import StringType, DateTimeType
from choicesenum import ChoicesEnum
from choicesenum.schematics.types import ChoicesEnumType

class HttpStatus(ChoicesEnum):
    OK = 200
    BAD_REQUEST = 400
    UNAUTHORIZED = 401
    FORBIDDEN = 403

class CustomSchematicModel(SchematicModel):
    name = StringType(required=True, max_length=255)
    created = DateTimeType(required=True, formats=('%d/%m/%Y', ''))
    http = ChoicesEnumType(HttpStatuses, required=True)