How to set the default of a JSONField to empty list in Django and django-jsonfield?

Question

What is the best way to set a JSONField to have the default value of a new list in django?

Context

There is a model where one of the fields is a list of items. In the case where there are no items set, the model should have an empty list.

Current solution

from django.models import Model

class MyModel(Model):
    the_list_field = JSONField(default=[])

Is this the best way to do it? Should it be switched to use list instead?

Thanks!

Solution

According to the Django documentation for JSONField you should indeed use default=list because using default=[] would create a mutable object that is shared between all instances of your field and could lead to some objects not having an empty list as a default.

Please note that this does not only apply for django.contrib.postgres.fields.JSONField but for all other kinds of objects and functions in Python in general.

Quote from the docs:

If you give the field a default, ensure it’s a callable such as list (for an empty default) or a callable that returns a list (such as a function). Incorrectly using default=[] creates a mutable default that is shared between all instances of