Django Enum¶

Tip

See Migration from 1.x -> 2.x for how to update from 1.x to 2.x.

Full and natural support for PEP435 enumerations as Django model fields.

Many packages aim to ease usage of Python enumerations as model fields. Most were superseded when Django provided TextChoices and IntegerChoices types. The motivation for django-enum was to:

Work with any Enum including those that do not derive from Django’s TextChoices and IntegerChoices.
Coerce fields to instances of the Enum type by default.
Allow strict adherence to Enum values to be disabled.
Handle migrations appropriately. (See Write Migrations)
Integrate as fully as possible with Django’s existing level of enum support.
Support Enum Properties to enable richer enumeration types. (A less awkward alternative to dataclass enumerations with more features)
Represent enum fields with the smallest possible column type.
Support bit field queries using standard Python Flag enumerations.
Be as simple and light-weight an extension to core Django as possible.
Enforce enumeration value consistency at the database level using check constraints by default.
(TODO) Support native database enumeration column types when available.

django-enum provides a new model field type, EnumField, that allows you to treat almost any PEP435 enumeration as a database column. EnumField resolves the correct native Django field type for the given enumeration based on its value type and range. For example, IntegerChoices that contain values between 0 and 32767 become PositiveSmallIntegerField.

from django.db import models
from django_enum import EnumField


class BasicExample(models.Model):

    class TextEnum(models.TextChoices):

        VALUE0 = "V0", "Value 0"
        VALUE1 = "V1", "Value 1"
        VALUE2 = "V2", "Value 2"

    class IntEnum(models.IntegerChoices):

        # fmt: off
        ONE   = 1, "One"
        TWO   = 2, "Two"
        THREE = 3, "Three"
        # fmt: on

    # this is equivalent to:
    #  CharField(max_length=2, choices=TextEnum.choices, null=True, blank=True)
    txt_enum = EnumField(TextEnum, null=True, blank=True, default=None)

    # this is equivalent to
    #  PositiveSmallIntegerField(choices=IntEnum.choices, default=IntEnum.ONE.value)
    int_enum = EnumField(IntEnum, default=IntEnum.ONE)

EnumField is more than just an alias. The fields are now assignable and accessible as their enumeration type rather than by-value:

instance = BasicExample.objects.create(
    txt_enum=BasicExample.TextEnum.VALUE1,
    int_enum=3  # by-value assignment also works
)

assert instance.txt_enum is BasicExample.TextEnum('V1')
assert instance.txt_enum.label == 'Value 1'

assert instance.int_enum is BasicExample.IntEnum.THREE
assert instance.int_enum.value == 3

Flag Support (BitFields)¶

enum.Flag types are also seamlessly supported! This allows a database column to behave like a bit field and is an alternative to having multiple boolean columns. There are positive performance implications for using a bit field instead of booleans proportional on the size of the bit field and the types of queries you will run against it. For bit fields more than a few bits long the size reduction both speeds up queries and reduces the required storage space. See the documentation for discussion and benchmarks.

from django.db import models
from enum import IntFlag
from django_enum import EnumField


class Permissions(IntFlag):

    # fmt: off
    READ    = 1<<0
    WRITE   = 1<<1
    EXECUTE = 1<<2
    # fmt: on


class FlagExample(models.Model):

    permissions = EnumField(Permissions, null=True, blank=True)

instance = FlagExample.objects.create(
    permissions=Permissions.READ | Permissions.WRITE | Permissions.EXECUTE
)

# get all models with at least RW:
assert instance in FlagExample.objects.filter(
    permissions__has_all=Permissions.READ | Permissions.WRITE
)

Note

The has_all and has_any field lookups are only available for Flag enumerations.

Enums with Properties¶

django-enum supports enum types that do not derive from Django’s IntegerChoices and TextChoices. This allows us to use other libs like Enum Properties which makes possible very rich enumeration fields:

> pip install enum-properties

import typing as t
from django.db import models
from enum_properties import Symmetric, StrEnumProperties
from typing_extensions import Annotated
from django_enum import EnumField


class PropertyExample(models.Model):

    class Color(StrEnumProperties):

        label: str
        rgb: Annotated[t.Tuple[int, int, int], Symmetric()]
        hex: Annotated[str, Symmetric(case_fold=True)]

        # fmt: off
        # name value label       rgb       hex
        RED   = "R", "Red",   (1, 0, 0), "ff0000"
        GREEN = "G", "Green", (0, 1, 0), "00ff00"
        BLUE  = "B", "Blue",  (0, 0, 1), "0000ff"
        # fmt: on

        # any type hints before the values in the Enum's definition become
        # properties on each value, and the enumeration value may be
        # instantiated from any symmetric property's value

    color = EnumField(Color)

instance = PropertyExample.objects.create(
    color=PropertyExample.Color('FF0000')
)
assert instance.color is PropertyExample.Color['RED']
assert instance.color is PropertyExample.Color('R')
assert instance.color is PropertyExample.Color((1, 0, 0))
# note that we did not make label symmetric, so this does not work:
# PropertyExample.Color('Red')

# direct comparison to any symmetric value also works
assert instance.color == 'FF0000'
assert instance.color == 'R'
assert instance.color == (1, 0, 0)
assert instance.color != 'Red'  # because label is not symmetric

# save by any symmetric value
instance.color = 'FF0000'

# access any enum property right from the model field
assert instance.color.hex == 'ff0000'

# this also works!
assert instance.color == 'ff0000'

# and so does this!
assert instance.color == 'FF0000'

instance.save()

# filtering works by any symmetric value or enum type instance
assert PropertyExample.objects.filter(
    color=PropertyExample.Color.RED
).first() == instance

assert PropertyExample.objects.filter(color=(1, 0, 0)).first() == instance

assert PropertyExample.objects.filter(color='FF0000').first() == instance

While they should be unnecessary, if you need to integrate with code that expects an interface fully compatible with Django’s TextChoices and IntegerChoices django-enum provides TextChoices, IntegerChoices, FlagChoices and FloatChoices types that derive from Enum Properties and Django’s Choices. So the above enumeration could also be written:

from django_enum.choices import TextChoices

class ChoicesWithProperties(models.Model):

    class Color(TextChoices):

        # label is added as a symmetric property by the base class
        rgb: Annotated[t.Tuple[int, int, int], Symmetric()]
        hex: Annotated[str, Symmetric(case_fold=True)]

        # fmt: off
        # name value label       rgb       hex
        RED   = "R", "Red",   (1, 0, 0), "ff0000"
        GREEN = "G", "Green", (0, 1, 0), "00ff00"
        BLUE  = "B", "Blue",  (0, 0, 1), "0000ff"
        # fmt: on

    color = EnumField(Color)

Installation¶

Clone django-enum from GitHub or install a release off PyPI:

> pip install django-enum

django-enum has several optional dependencies that are not installed by default. EnumField works seamlessly with all Django apps that work with model fields with choices without any additional work. Optional integrations are provided with several popular libraries to extend this basic functionality, these include:

enum-properties

> pip install "django-enum[properties]"

django-filter
djangorestframework.

Database Support¶

Like with Django, PostgreSQL is the preferred database for support. The full test suite is run against all combinations of currently supported versions of Django, Python, and PostgreSQL as well as psycopg3 and psycopg2. The other RDBMS supported by Django are also tested including SQLite, MySQL, MariaDB and Oracle. For these RDBMS (with the exception of Oracle), tests are run against the minimum and maximum supported version combinations to maximize coverage breadth.

See the latest test runs for our current test matrix

Note

For Oracle, only the latest version of the free database is tested against the minimum and maximum supported versions of Python, Django and the cx-Oracle driver.

Django Enum¶

Flag Support (BitFields)¶

Enums with Properties¶

Installation¶

Database Support¶

Further Reading¶