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#!/usr/bin/env python | |
# -*- coding:utf-8 -*- | |
# Stolen from: https://mlvin.xyz/django-single-file-project.html | |
import datetime | |
import inspect | |
import os | |
import sys | |
from types import ModuleType | |
import django | |
from django.conf import settings | |
BASE_DIR = os.path.dirname(os.path.abspath(__file__)) | |
# The current name of the file, which will be the name of our app | |
APP_LABEL, _ = os.path.splitext(os.path.basename(os.path.abspath(__file__))) | |
# Migrations folder need to be created, and django needs to be told where it is | |
APP_MIGRATION_MODULE = '%s_migrations' % APP_LABEL | |
APP_MIGRATION_PATH = os.path.join(BASE_DIR, APP_MIGRATION_MODULE) | |
# Create the folder and a __init__.py if they don't exist | |
if not os.path.exists(APP_MIGRATION_PATH): | |
os.makedirs(APP_MIGRATION_PATH) | |
open(os.path.join(APP_MIGRATION_PATH, '__init__.py'), 'w').close() | |
# Hack to trick Django into thinking this file is actually a package | |
sys.modules[APP_LABEL] = sys.modules[__name__] | |
sys.modules[APP_LABEL].__path__ = [os.path.abspath(__file__)] | |
settings.configure( | |
DEBUG=True, | |
ROOT_URLCONF='%s.urls' % APP_LABEL, | |
MIDDLEWARE=(), | |
INSTALLED_APPS=[APP_LABEL], | |
MIGRATION_MODULES={APP_LABEL: APP_MIGRATION_MODULE}, | |
SITE_ID=1, | |
DATABASES={ | |
'default': { | |
'ENGINE': 'django.db.backends.sqlite3', | |
'NAME': os.path.join(BASE_DIR, 'db.sqlite3'), | |
} | |
}, | |
LOGGING={ | |
'version': 1, | |
'disable_existing_loggers': False, | |
'formatters': { | |
'simple': { | |
'format': "%(levelname)s %(message)s", | |
}, | |
}, | |
'handlers': { | |
'console': { | |
'level': 'DEBUG', | |
'class': 'logging.StreamHandler', | |
'formatter': 'simple', | |
} | |
}, | |
'loggers': { | |
'django.db.backends': {'handlers': ['console'], 'level': 'DEBUG', 'propagate': False}, | |
'django.db.backends.schema': {'level': 'ERROR'}, # Causes sql logs to duplicate -- really annoying | |
} | |
}, | |
STATIC_URL='/static/' | |
) | |
django.setup() | |
from django.apps import apps # noqa: E402 isort:skip | |
# Setup the AppConfig so we don't have to add the app_label to all our models | |
def get_containing_app_config(module): | |
if module == '__main__': | |
return apps.get_app_config(APP_LABEL) | |
return apps._get_containing_app_config(module) | |
apps._get_containing_app_config = apps.get_containing_app_config | |
apps.get_containing_app_config = get_containing_app_config | |
# Your code below this line | |
# ############################################################################## | |
from django.db import models # noqa: E402 isort:skip | |
from django.test import TestCase # noqa: E402 isort:skip | |
class ModelA(models.Model): | |
somecriteria = models.CharField(max_length=50) | |
class ModelB(models.Model): | |
somerelation = models.ForeignKey(ModelA, on_delete=models.CASCADE) | |
someattribute = models.CharField(max_length=50) | |
urlpatterns = [] | |
class SimpleTestCase(TestCase): | |
def setUp(self): | |
one = ModelA.objects.create(somecriteria='1') | |
ModelB.objects.create(somerelation=one, someattribute='1') | |
ModelB.objects.create(somerelation=one, someattribute='2') | |
ModelB.objects.create(somerelation=one, someattribute='1') | |
two = ModelA.objects.create(somecriteria='2') | |
ModelB.objects.create(somerelation=two, someattribute='2') | |
ModelB.objects.create(somerelation=two, someattribute='1') | |
three = ModelA.objects.create(somecriteria='3') | |
# Note this doesn't have any ModelB intensionally | |
def test_solution(self): | |
from django.db import models # needs to be here becuase of the hack that is having a single django file # noqa | |
expected = [('1', ['1', '1']), ('2', ['2']), ('3', [])] | |
actual = [] | |
with self.assertNumQueries(2): | |
modelb_qs = models.Subquery(ModelB.objects.filter(someattribute=models.OuterRef('somerelation__somecriteria')).values('id')) | |
qs = ModelA.objects.prefetch_related(models.Prefetch('modelb_set', queryset=ModelB.objects.filter(id__in=modelb_qs))) | |
for obj in qs: | |
temp = (obj.somecriteria, []) | |
if len(obj.modelb_set.all()): | |
temp[1].extend([x.someattribute for x in obj.modelb_set.all()]) | |
actual.append(temp) | |
self.assertEqual(actual, expected) | |
# Your code above this line | |
# ############################################################################## | |
# Used so you can do 'from <name of file>.models import *' | |
models_module = ModuleType('%s.models' % (APP_LABEL)) | |
tests_module = ModuleType('%s.tests' % (APP_LABEL)) | |
urls_module = ModuleType('%s.urls' % (APP_LABEL)) | |
urls_module.urlpatterns = urlpatterns | |
for variable_name, value in list(locals().items()): | |
# We are only interested in models | |
if inspect.isclass(value) and issubclass(value, models.Model): | |
setattr(models_module, variable_name, value) | |
# We are only interested in tests | |
if inspect.isclass(value) and issubclass(value, TestCase): | |
setattr(tests_module, variable_name, value) | |
# Setup the fake modules | |
sys.modules[models_module.__name__] = models_module | |
sys.modules[tests_module.__name__] = tests_module | |
sys.modules[urls_module.__name__] = urls_module | |
sys.modules[APP_LABEL].models = models_module | |
sys.modules[APP_LABEL].tests = tests_module | |
sys.modules[APP_LABEL].urls = urls_module | |
if __name__ == "__main__": | |
# Hack to fix tests | |
argv = [arg for arg in sys.argv if not arg.startswith('-')] | |
if len(argv) == 2 and argv[1] == 'test': | |
sys.argv.append(APP_LABEL) | |
from django.core.management import execute_from_command_line | |
execute_from_command_line(sys.argv) | |
else: | |
from django.core.wsgi import get_wsgi_application | |
get_wsgi_application() |
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In order to run the code above run the following:
If you want the REAL copy and paste version:
Answers stackoverflow question: https://stackoverflow.com/questions/57461476/prefetch-related-with-a-filter-that-contains-a-field-of-the-original-model/57463113#57463113