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Introduction to demo fixtures

A fixture, in real life, is a piece of furniture in a house, such as a kitchen, that is considered an integral part of the house. Django uses the word to designate a collection of data records that can be loaded into the database of a new site.

Fixtures are part of the application code

Every plugin can have a subdirectory named fixtures.


A subdirectory of a plugin that contains a number of fixture files in different formats. Django will discover this directory when you run the loaddata command. Read more about it in the Django documentation.

In Lino we usually don’t write fixtures in XML or JSON but in Python. That’s why our fixtures directories also contain a __init__.py file.

Demo fixtures

Lino extends Django’s fixtures by defining the concept of demo fixtures.

demo fixtures

The list of fixtures to be loaded by pm prep when a new Lino site gets installed.

For example, the chatter application has the following value for this attribute:

>>> from lino_book.projects.chatter.settings import Site
>>> Site.demo_fixtures
['std', 'demo', 'demo2']

This means that saying pm prep on a site that runs chatter is equivalent to saying pm initdb std demo demo2

If the new site runs a Lino Così, the list of demo fixtures is different:

>>> from lino_cosi.lib.cosi.settings import Site
>>> Site.demo_fixtures
['std', 'minimal_ledger', 'furniture', 'demo', 'demo2', 'demo3', 'checkdata']

The list of demo fixtures of an application is defined by the application developer in the demo_fixtures site attribute.

The advantage of this approach is that the system administrator doesn’t need to know the list of demo fixtures when setting up a Lino site. The default list of demo fixtures to load for initializing a “clean” demo database can be long and difficult to remember, and (more importantly) it can change when an application evolves. As a system administrator you usually don’t want to know such details.

As a future application developer you can learn more about them in Writing Python fixtures.