Re: Django 1.9 Apps aren't loaded yet

On Mon, Apr 25, 2016 at 8:13 AM, <marcin.j.nowak@gmail.com> wrote:

The initialization process of models seems to be good step in cleaning many problems, but I don't understant why I can't import models.

The usage of the model should raise exception when it is not loaded/initialized, but not importing a model class!

Django needs to maintain a registry of all the models found in all the installed applications, and it needs each model to go into that registry once and only once (you don't want a model being registered multiple times). This requires there to be some period in time during which models are essentially "locked", so that Django has the ability to build the model registry without any other code interfering or causing duplicate copies of model classes to be floating around from stray import statements. That period occurs as Django is starting up, and until it's done you are not permitted to do anything that imports a model class.

Typically the only way to actually run into a problem with this is to be importing models inside the __init__.py file of an application, since that causes an import at the time Django is loading and inspecting the application. Avoiding imports of models at the top level of __init__.py is the solution to this (and code which needs to get a list of all applications/models should just use the API Django exposes for that rather than trying to do all the imports itself; there's a reason why Django provides introspection APIs for this).

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