CharacterSeparatedField - A Django REST framework field that separates a string with a given separator into a native list and reverts a list into a string separated with a given separator.

fields.py

from rest_framework import serializers


class CharacterSeparatedField(serializers.WritableField):
    """
    A field that separates a string with a given separator into
    a native list and reverts a list into a string separated with a given
    separator.
    """
    def __init__(self, *args, **kwargs):
        self.separator = kwargs.pop('separator', ',')
        super(CharacterSeparatedField, self).__init__(*args, **kwargs)

    def to_native(self, obj):
        if obj:
            return self.separator.join(obj)

    def from_native(self, data):
        return data.split(self.separator)

    def run_validators(self, value):
        for val in value:
            super(CharacterSeparatedField, self).run_validators(val)
  

tests.py

from django.test import TestCase

from .fields import CharacterSeparatedField


class CharacterSeparatedFieldTestCase(TestCase):
    def test_field_default_separator_is_comma(self):
        """
        Tests that field should have a default comma separator specified.
        """
        field = CharacterSeparatedField()
        self.assertEqual(field.separator, ',')

    def test_field_should_accept_custom_separator(self):
        """
        Tests that field should accept a custom separator.
        """
        field = CharacterSeparatedField(separator='.')
        self.assertEqual(field.separator, '.')

    def test_field_to_native_should_return_str_for_given_list(self):
        """
        Tests that field's to_native method should return a string
        from a specified list.
        """
        field = CharacterSeparatedField()
        self.assertEqual(field.to_native(['a', 'b', 'c']), 'a,b,c')

    def test_field_from_native_should_return_list_for_given_str(self):
        """
        Tests that field's from_native method should return a list
        from a specified string.
        """
        field = CharacterSeparatedField()
        self.assertEqual(field.from_native('a,b,c'), ['a', 'b', 'c'])

@jpadilla @tomchristie here is my take on this https://gist.github.com/imomaliev/77fdfd0ab5f1b324f4e496768534737e