List field in model?

In my model, I want a field that has a list of triplets. e.g. [[1, 3, 4], [4, 2, 6], [8, 12, 3], [3, 3, 9]]. Is there a field that can store this data in the database?

Solution 1:

You can convert it into string by using JSON and store it as string.

For example,

In [3]: json.dumps([[1, 3, 4], [4, 2, 6], [8, 12, 3], [3, 3, 9]])

Out[3]: '[[1, 3, 4], [4, 2, 6], [8, 12, 3], [3, 3, 9]]'

You can add a method into your class to convert it automatically for you.

import json


class Foobar(models.Model):
    foo = models.CharField(max_length=200)

    def set_foo(self, x):
        self.foo = json.dumps(x)

    def get_foo(self):
        return json.loads(self.foo)

If you're using Django 1.9 or above, and you use postgresql, there is a new class called JSONField, you should use it instead. Here is a link to it

There is a good talk about PostgreSQL JSONs and Arrays on youtube. Watch it, it has very good information.

Solution 2:

If you're on Django 1.10 or newer AND Postgres as your database, you can use ArrayField. It's better to use than django-taggit or other alternatives, as it's native to the Django framework. https://docs.djangoproject.com/en/3.1/ref/contrib/postgres/fields/#arrayfield

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,
    )

If you're on Django 3.1 or newer they've added support for JSONField with most database backends (MariaDB 10.2.7+, MySQL 5.7.8+, Oracle, PostgreSQL, and SQLite 3.9.0+). You can use this to store your Array!

https://docs.djangoproject.com/en/3.1/ref/models/fields/#jsonfield

from django.db import models

class ChessBoard(models.Model):
    list_of_pieces = models.JSONField()