253 lines
9.5 KiB
Python
253 lines
9.5 KiB
Python
"Utilities for loading models and the modules that contain them."
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from django.conf import settings
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from django.core.exceptions import ImproperlyConfigured
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from django.utils.datastructures import SortedDict
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from django.utils.importlib import import_module
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from django.utils.module_loading import module_has_submodule
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import sys
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import os
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import threading
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__all__ = ('get_apps', 'get_app', 'get_models', 'get_model', 'register_models',
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'load_app', 'app_cache_ready')
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class AppCache(object):
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"""
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A cache that stores installed applications and their models. Used to
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provide reverse-relations and for app introspection (e.g. admin).
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"""
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# Use the Borg pattern to share state between all instances. Details at
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# http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66531.
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__shared_state = dict(
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# Keys of app_store are the model modules for each application.
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app_store = SortedDict(),
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# Mapping of installed app_labels to model modules for that app.
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app_labels = {},
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# Mapping of app_labels to a dictionary of model names to model code.
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# May contain apps that are not installed.
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app_models = SortedDict(),
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# Mapping of app_labels to errors raised when trying to import the app.
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app_errors = {},
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# -- Everything below here is only used when populating the cache --
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loaded = False,
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handled = {},
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postponed = [],
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nesting_level = 0,
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write_lock = threading.RLock(),
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_get_models_cache = {},
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)
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def __init__(self):
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self.__dict__ = self.__shared_state
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def _populate(self):
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"""
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Fill in all the cache information. This method is threadsafe, in the
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sense that every caller will see the same state upon return, and if the
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cache is already initialised, it does no work.
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"""
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if self.loaded:
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return
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self.write_lock.acquire()
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try:
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if self.loaded:
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return
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for app_name in settings.INSTALLED_APPS:
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if app_name in self.handled:
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continue
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self.load_app(app_name, True)
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if not self.nesting_level:
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for app_name in self.postponed:
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self.load_app(app_name)
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self.loaded = True
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finally:
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self.write_lock.release()
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def _label_for(self, app_mod):
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"""
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Return app_label for given models module.
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"""
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return app_mod.__name__.split('.')[-2]
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def load_app(self, app_name, can_postpone=False):
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"""
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Loads the app with the provided fully qualified name, and returns the
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model module.
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"""
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self.handled[app_name] = None
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self.nesting_level += 1
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app_module = import_module(app_name)
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try:
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models = import_module('.models', app_name)
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except ImportError:
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self.nesting_level -= 1
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# If the app doesn't have a models module, we can just ignore the
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# ImportError and return no models for it.
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if not module_has_submodule(app_module, 'models'):
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return None
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# But if the app does have a models module, we need to figure out
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# whether to suppress or propagate the error. If can_postpone is
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# True then it may be that the package is still being imported by
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# Python and the models module isn't available yet. So we add the
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# app to the postponed list and we'll try it again after all the
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# recursion has finished (in populate). If can_postpone is False
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# then it's time to raise the ImportError.
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else:
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if can_postpone:
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self.postponed.append(app_name)
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return None
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else:
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raise
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self.nesting_level -= 1
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if models not in self.app_store:
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self.app_store[models] = len(self.app_store)
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self.app_labels[self._label_for(models)] = models
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return models
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def app_cache_ready(self):
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"""
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Returns true if the model cache is fully populated.
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Useful for code that wants to cache the results of get_models() for
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themselves once it is safe to do so.
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"""
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return self.loaded
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def get_apps(self):
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"Returns a list of all installed modules that contain models."
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self._populate()
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# Ensure the returned list is always in the same order (with new apps
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# added at the end). This avoids unstable ordering on the admin app
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# list page, for example.
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apps = [(v, k) for k, v in self.app_store.items()]
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apps.sort()
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return [elt[1] for elt in apps]
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def get_app(self, app_label, emptyOK=False):
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"""
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Returns the module containing the models for the given app_label. If
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the app has no models in it and 'emptyOK' is True, returns None.
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"""
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self._populate()
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self.write_lock.acquire()
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try:
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for app_name in settings.INSTALLED_APPS:
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if app_label == app_name.split('.')[-1]:
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mod = self.load_app(app_name, False)
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if mod is None:
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if emptyOK:
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return None
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raise ImproperlyConfigured("App with label %s is missing a models.py module." % app_label)
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else:
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return mod
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raise ImproperlyConfigured("App with label %s could not be found" % app_label)
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finally:
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self.write_lock.release()
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def get_app_errors(self):
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"Returns the map of known problems with the INSTALLED_APPS."
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self._populate()
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return self.app_errors
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def get_models(self, app_mod=None,
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include_auto_created=False, include_deferred=False,
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only_installed=True):
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"""
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Given a module containing models, returns a list of the models.
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Otherwise returns a list of all installed models.
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By default, auto-created models (i.e., m2m models without an
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explicit intermediate table) are not included. However, if you
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specify include_auto_created=True, they will be.
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By default, models created to satisfy deferred attribute
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queries are *not* included in the list of models. However, if
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you specify include_deferred, they will be.
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"""
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cache_key = (app_mod, include_auto_created, include_deferred, only_installed)
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try:
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return self._get_models_cache[cache_key]
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except KeyError:
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pass
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self._populate()
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if app_mod:
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if app_mod in self.app_store:
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app_list = [self.app_models.get(self._label_for(app_mod),
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SortedDict())]
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else:
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app_list = []
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else:
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if only_installed:
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app_list = [self.app_models.get(app_label, SortedDict())
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for app_label in self.app_labels.iterkeys()]
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else:
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app_list = self.app_models.itervalues()
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model_list = []
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for app in app_list:
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model_list.extend(
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model for model in app.values()
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if ((not model._deferred or include_deferred) and
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(not model._meta.auto_created or include_auto_created))
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)
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self._get_models_cache[cache_key] = model_list
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return model_list
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def get_model(self, app_label, model_name,
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seed_cache=True, only_installed=True):
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"""
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Returns the model matching the given app_label and case-insensitive
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model_name.
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Returns None if no model is found.
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"""
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if seed_cache:
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self._populate()
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if only_installed and app_label not in self.app_labels:
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return None
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return self.app_models.get(app_label, SortedDict()).get(model_name.lower())
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def register_models(self, app_label, *models):
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"""
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Register a set of models as belonging to an app.
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"""
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for model in models:
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# Store as 'name: model' pair in a dictionary
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# in the app_models dictionary
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model_name = model._meta.object_name.lower()
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model_dict = self.app_models.setdefault(app_label, SortedDict())
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if model_name in model_dict:
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# The same model may be imported via different paths (e.g.
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# appname.models and project.appname.models). We use the source
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# filename as a means to detect identity.
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fname1 = os.path.abspath(sys.modules[model.__module__].__file__)
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fname2 = os.path.abspath(sys.modules[model_dict[model_name].__module__].__file__)
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# Since the filename extension could be .py the first time and
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# .pyc or .pyo the second time, ignore the extension when
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# comparing.
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if os.path.splitext(fname1)[0] == os.path.splitext(fname2)[0]:
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continue
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model_dict[model_name] = model
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self._get_models_cache.clear()
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cache = AppCache()
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# These methods were always module level, so are kept that way for backwards
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# compatibility.
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get_apps = cache.get_apps
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get_app = cache.get_app
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get_app_errors = cache.get_app_errors
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get_models = cache.get_models
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get_model = cache.get_model
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register_models = cache.register_models
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load_app = cache.load_app
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app_cache_ready = cache.app_cache_ready
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