How To Run Arbitrary Code After Django is “Fully Loaded”

Question

I need to perform some fairly simple tasks after my Django environment has been \"fully loaded\".

More specifically I need to do things like Signal.disconnect(

Answer 1

I had to do the following monkey patching. I use django 1.5 from github branch. I don't know if that's the proper way to do it, but it works for me.

I couldn't use middleware, because i also wanted the manage.py scripts to be affected.

anyway, here's this rather simple patch:

import django
from django.db.models.loading import AppCache

django_apps_loaded = django.dispatch.Signal()

def populate_with_signal(cls):
    ret = cls._populate_orig()
    if cls.app_cache_ready():
        if not hasattr(cls, '__signal_sent'):
            cls.__signal_sent = True
            django_apps_loaded.send(sender=None)
    return ret

if not hasattr(AppCache, '_populate_orig'):
    AppCache._populate_orig = AppCache._populate
    AppCache._populate = populate_with_signal

and then you could use this signal like any other:

def django_apps_loaded_receiver(sender, *args, **kwargs):
    # put your code here.
django_apps_loaded.connect(django_apps_loaded_receiver)

Answer 2

My question is a more poorly phrased duplicate of this question: Where To Put Django Startup Code. The answer comes from that question:

Write middleware that does this in init and afterwards raise django.core.exceptions.MiddlewareNotUsed from the init, django will remove it for all requests...

See the Django documentation on writing your own middleware.

Answer 3

In Django 1.7 Apps can implement the ready() method: https://docs.djangoproject.com/en/dev/ref/applications/#django.apps.AppConfig.ready

Answer 4

As far as I know there's no such thing as "fully loaded". Plenty of Django functions include import something right in the function. Those imports will only happen if you actually invoke that function. The only way to do what you want would be to explicitly import the things you want to patch (which you should be able to do anywhere) and then patch them. Thereafter any other imports will re-use them.