Wsrtjtyk

If you are using PostgreSQL, you can use ArrayField with a nested ArrayField: https://docs.djangoproject.com/en/1.8/ref/contrib/postgres/fields/

This way, the data structure will be known to the underlying database. Also, the ORM brings special functionality for it.

Note that you will have to create a GIN index by yourself, though (see the above link, further down: https://docs.djangoproject.com/en/1.8/ref/contrib/postgres/fields/#indexing-arrayfield).

If you're using a more modern version of Django like 1.10 and your DB is Postgres, there is a new ArrayField that is better to use than django-taggit or other alternatives, as it's native to the Django framework.

from django.db import models

from django.contrib.postgres.fields import ArrayField



class ChessBoard(models.Model):

    board = ArrayField(

        ArrayField(

            models.CharField(max_length=10, blank=True),

            size=8,

        ),

        size=8,

    )

I think it will help you.

from django.db import models

import ast



class ListField(models.TextField):

    __metaclass__ = models.SubfieldBase

    description = "Stores a python list"



    def __init__(self, *args, **kwargs):

        super(ListField, self).__init__(*args, **kwargs)



    def to_python(self, value):

        if not value:

            value = 



        if isinstance(value, list):

            return value



        return ast.literal_eval(value)



    def get_prep_value(self, value):

        if value is None:

            return value



        return unicode(value)



    def value_to_string(self, obj):

        value = self._get_val_from_obj(obj)

        return self.get_db_prep_value(value)



class ListModel(models.Model):

    test_list = ListField()

Example :

>>> ListModel.objects.create(test_list= [[1,2,3], [2,3,4,4]])



>>> ListModel.objects.get(id=1)



>>> o = ListModel.objects.get(id=1)

>>> o.id

1L

>>> o.test_list

[[1, 2, 3], [2, 3, 4, 4]]

>>> 

Just use a JSON field that these third-party packages provide:

• django-jsonfield


• django-annoying

In this case, you don't need to care about the field value serialization - it'll happen under-the-hood.

Hope that helps.

You can flatten the list and then store the values to a CommaSeparatedIntegerField. When you read back from the database, just group the values back into threes.

Disclaimer: according to database normalization theory, it is better not to store collections in single fields; instead you would be encouraged to store the values in those triplets in their own fields and link them via foreign keys. In the real world, though, sometimes that is too cumbersome/slow.

If you are using Google App Engine or MongoDB as your backend, and you are using the djangoappengine library, there is a built in ListField that does exactly what you want. Further, it's easy to query the Listfield to find all objects that contain an element in the list.

With my current reputation I have no ability to comment, so I choose answer referencing comments for sample code in reply by Prashant Gaur (thanks, Gaur - this was helpful!) - his sample is for python2, since python3 has no

unicode

The replacement below for function

get_prep_value(self, value):

encoding='utf-8', errors='ignore'

decode()

unicode() methods

errors='ignore'

import sys



...



    def get_prep_value(self, value):

        if value is None:

            return value

        if sys.version_info[0] >= 3:

            if isinstance(out_data, type(b'')):

                return value.decode(encoding='utf-8', errors='ignore')

        else:

            if isinstance(out_data, type(b'')):

                return unicode(value, encoding='utf-8', errors='ignore')

        return str(value)

...

It's quite an old topic, but since it is returned when searching for "django list field" I'll share the custom django list field code I modified to work with Python 3 and Django 2. It supports the admin interface now and not uses eval (which is a huge security breach in Prashant Gaur's code).

from django.db import models

from typing import Iterable



class ListField(models.TextField):

    """

    A custom Django field to represent lists as comma separated strings

    """



    def __init__(self, *args, **kwargs):

        self.token = kwargs.pop('token', ',')

        super().__init__(*args, **kwargs)



    def deconstruct(self):

        name, path, args, kwargs = super().deconstruct()

        kwargs['token'] = self.token

        return name, path, args, kwargs



    def to_python(self, value):



        class SubList(list):

            def __init__(self, token, *args):

                self.token = token

                super().__init__(*args)



            def __str__(self):

                return self.token.join(self)



        if isinstance(value, list):

            return value

        if value is None:

            return SubList(self.token)

        return SubList(self.token, value.split(self.token))



    def from_db_value(self, value, expression, connection):

        return self.to_python(value)



    def get_prep_value(self, value):

        if not value:

            return

        assert(isinstance(value, Iterable))

        return self.token.join(value)



    def value_to_string(self, obj):

        value = self.value_from_object(obj)

        return self.get_prep_value(value)