dynamically loading django apps at runtime

Is it possible to dynamically load Django apps at runtime? Usually, apps are loaded at initialization, using the INSTALLED_APPS tuple in settings.py. However, is it possible to load additional apps at runtime? I am encountering this issue in different situations. One situation, for example, arises during testing, when I would like to dynamically load or unload apps.

In order to make the problem more concrete, imagine I have a directory called apps where I put my apps and I would like to automatically install any new app that goes in there without manually editing the settings.py.

This is easy enough. Following the example code in

Django: Dynamically add apps as plugin, building urls and other settings automatically

we put the following code in settings.py to could loop over the names of all sub-directories in the app directory and increment the INSTALLED_APPS tuple in settings.py like this:

APPS_DIR = '/path_to/apps/'

for item in os.listdir(APPS_DIR):
    if os.path.isdir(os.path.join(APPS_DIR, item)):
        app_name = 'apps.%s' % item
    if app_name not in INSTALLED_APPS:
        INSTALLED_APPS += (app_name, )

After that, if I was in a Django shell, I could something like

from django.conf import settings

and the apps would be listed in settings.INSTALLED_APPS. And if I did

from django.core import management
management.call_command('syncdb', interactive=False)

that would create the necessary DB tables for the apps.

However, if I were to now add some more apps to the apps/ directory, without re-starting, these would not be listed in settings.INSTALLED_APPS, and so a subsequent call to the syncdb would have no effect.

What I would like to know is if there is something I could do --- without restarting --- to reload the settings and load/install new apps.

I have tried to directly import my settings.py, i.e. from myproject import settings

and then reload that settings using the python builtin after any app directory changes. Although settings.INSTALLED_APPS is now changed to include the newly added apps, this ultimately makes no difference. For example,

from django.db import models
models.get_apps()

shows only the original apps in apps and not the newly added ones and likewise

management.call_command('syncdb', interactive=False)

will not see the newly added apps.

As I stated above, I am thinking about this situation particularly in the context of testings where I dynamically would add or remove apps.

Ps. I working with Django 1.6, but on the advice of @RickyA, I see that there are some substantial changes to Django's treatment of applications in 1.7

https://docs.djangoproject.com/en/1.7/ref/applications/

I'm still not sure what this might mean for the problem I am facing.

To answer my own question...

While I do not have a completely general solution to this problem, I do have one that is sufficient for the purposes of dynamically loading apps during testing.

The basic solution is simple, and I found it at a wee little bixly blog.

Continuing with my example above, if I was in a django shell and wanted to add and load some new apps that were added to my apps directory, I could do

import os
from django.conf import settings
from django.db.models import loading
from django.core import management

APPS_DIR = '/path_to/apps/'

for item in os.listdir(APPS_DIR):
    if os.path.isdir(os.path.join(APPS_DIR, item)):
        app_name = 'apps.%s' % item
    if app_name not in settings.INSTALLED_APPS:
        settings.INSTALLED_APPS += (app_name, )

and then

loading.cache.loaded = False
management.call_command('syncdb', interactive=False)