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Custom Django field for using enumerations of named constants

Project description

Thi package is based on django-enumfield. It was extended to make django form filters happy at the time of validating input for named attributes rather than for enumerated values like 1,2,…

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Installation

Install django-enumfield-named-choices in your Python environment:

$ pip install django-enumfield-named-choices

Usage

Create an Enum-class and pass it as first argument to the Django model EnumField.

from django.db import models
from django_enumfield_named_choices import enum

class BeerStyle(enum.Enum):
    LAGER = 0
    STOUT = 1
    WEISSBIER = 2

class Beer(models.Model):
    style = enum.EnumField(BeerStyle, default=BeerStyle.LAGER)
Beer.objects.create(style=BeerStyle.STOUT)
Beer.objects.filter(style=BeerStyle.STOUT)

You can use your own labels for Enum items

class Animals(enum.Enum):
    CAT = 1
    DOG = 2

    labels = {
        CAT: 'Cat',
        DOG: 'Dog'
    }

The Enum-class provides the possibility to use transition validation.

from django.db import models
from django_enumfield_named_choices import enum

class PersonStatus(enum.Enum):
    ALIVE = 1
    DEAD = 2
    REANIMATED = 3

    _transitions = {
        DEAD: (ALIVE,),
        REANIMATED: (DEAD,)
    }

class Person(models.Model):
    status = enum.EnumField(PersonStatus)

These transitions state that a PersonStatus can only go to DEAD from ALIVE and to REANIMATED from DEAD.

person = Person.objects.create(status=PersonStatus.ALIVE)
try:
    person.status = PersonStatus.REANIMATED
    person.save()
except InvalidStatusOperationError:
    print("Person status can not go from ALIVE to REANIMATED")

The Enum-class can also be used without the EnumField. This is very useful in Django form ChoiceFields.

from django.forms import Form
from django_enumfield_named_choices import enum

class GenderEnum(enum.Enum):
    MALE = 1
    FEMALE = 2

    labels = {
        MALE: 'Male',
        FEMALE: 'Female',
    }

class PersonForm(forms.Form)
    gender = forms.TypedChoiceField(choices=GenderEnum.choices(), coerce=int)

Rendering PersonForm in a template will generate a select-box with “Male” and “Female” as option labels for the gender field.

If you want to use this package along with django restful framework and django-filter, django-url-filter, and djangorestframework-filters packages to make filtering on the named values of Enum type instead of their numerical counterparts you can use extra attribute on your enum type interface with value type str, by default it is set to int type as following.

# in enums.py

from django_enumfield_named_choices import enum

class GenderEnum(enum.Enum):
    MALE = 1
    FEMALE = 2

    labels = {
        MALE: 'Male',
        FEMALE: 'Female',
    }

    interface = str

# in models.py

from django_enumfield_named_choices.db.fields import EnumField

class Person(models.Model):
name = ...
gender = EnumField(GenderEnum)

# and then when you expose you model through API endpoint
# you can filter it with following URL request
# /person/?gender=male
# instead of
# /person/?gender=1
# thought the actual values of enum in the database are still integers.

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