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register_model is called exactly once in the entire Django code base, at the
bottom of ModelBase.__new__:
new_class._meta.apps.register_model(new_class._meta.app_label, new_class)
ModelBase.__new__ exits prematurely 120 lines earlier (sigh) if a model with
the same name is already registered:
if new_class._meta.apps.get_registered_model(new_class._meta.app_label, name):
return
(This isn't the exact code, but it's equivalent.)
apps.register_model and apps.get_registered_model are essentially a setter and
a getter for apps.all_models, and apps.register_model is the only setter. As a
consequence, new_class._meta.apps.all_models cannot change in-between.
Considering that name == new_class.__name__, we can conclude that
register_model(app_label, model) is always called with such arguments that
get_registered_model(app_label, model.__name__) returns None.
Considering that model._meta.model_name == model.__name__.lower(), and looking
at the implementation of register_model and get_registered_model, this proves
that self.all_models[app_label] doesn't contain model._meta.model_name in
register_model, allowing us to simplify the implementation.
Django is a high-level Python Web framework that encourages rapid development and clean, pragmatic design. Thanks for checking it out. All documentation is in the "docs" directory and online at http://docs.djangoproject.com/en/dev/. If you're just getting started, here's how we recommend you read the docs: * First, read docs/intro/install.txt for instructions on installing Django. * Next, work through the tutorials in order (docs/intro/tutorial01.txt, docs/intro/tutorial02.txt, etc.). * If you want to set up an actual deployment server, read docs/howto/deployment/index.txt for instructions. * You'll probably want to read through the topical guides (in docs/topics) next; from there you can jump to the HOWTOs (in docs/howto) for specific problems, and check out the reference (docs/ref) for gory details. * See docs/README for instructions on building an HTML version of the docs. Docs are updated rigorously. If you find any problems in the docs, or think they should be clarified in any way, please take 30 seconds to fill out a ticket here: http://code.djangoproject.com/newticket To get more help: * Join the #django channel on irc.freenode.net. Lots of helpful people hang out there. Read the archives at http://django-irc-logs.com/. * Join the django-users mailing list, or read the archives, at http://groups.google.com/group/django-users. To contribute to Django: * Check out http://www.djangoproject.com/community/ for information about getting involved. To run Django's test suite: * Follow the instructions in the "Unit tests" section of docs/internals/contributing/writing-code/unit-tests.txt, published online at https://docs.djangoproject.com/en/dev/internals/contributing/writing-code/unit-tests/#running-the-unit-tests