How to set initial data for Django admin model add instance form?

Alasdair's approach is nice but outdated. Radev's approach looks quite nice and as mentioned in the comment, it strikes me that there is nothing about this in the documentation.

Apart from those, since Django 1.7 there is a function get_changeform_initial_data in ModelAdmin that sets initial form values:

def get_changeform_initial_data(self, request):
    return {'name': 'custom_initial_value'}

You need to include self as the first argument in your __init__ method definition, but should not include it when you call the superclass' method.

def __init__(self, *args, **kwargs):
    # We can't assume that kwargs['initial'] exists! 
    if 'initial' not in kwargs:
        kwargs['initial'] = {}
    kwargs['initial'].update({'description': get_default_content()})
    super(FooAdminForm, self).__init__(*args, **kwargs)

Having said that, a model field can take a callable for its default, so you may not have to define a custom admin form at all.

class Foo(models.Model):
    title = models.CharField(max_length=50)
    description = models.TextField(default=get_default_content)