Integrate flask with django orm

django-orm.md

Django ORM

(https://gist.github.com/seanbehan/168a277a5a23086e76000a59e54fb3d5)

Integration into flask

1. Create manage.py and settings.py in the root directory. Then install the dependencies in your environment.

   pip install flask django dj-database-url psycopg2
   

   # manage.py
   import os
   import sys
   import dotenv
   
   dotenv.load_dotenv()
   
   if __name__ == "__main__":
       from django.core.management import execute_from_command_line
       execute_from_command_line(sys.argv)

   # settings.py
   import os
   import dj_database_url
   
   DATABASES = { 
       'default': dj_database_url.config(default=os.environ['DATABASE_URL']) 
   }
   
   INSTALLED_APPS = ( 'instagram', )
   
   SECRET_KEY = os.environ['SECRET_KEY']

   # .env
   
   DJANGO_SETTINGS_MODULE=settings
   DATABASE_URL="postgres://localhost:5432/<db_name>"
   SECRET_KEY=""

2. Create a folder with the name state in your INSTALLED_APPS and create the file in the folder as below.

   django-nextagram/
       instagram_api/
       instagram_web/
       instagram/
           migrations/
               __init__.py     # empty file 
           models/
               __init__.py     # import models
               base_model.py
               user.py
       .env
       app.py
       config.py
       manage.py
       settings.py
       ...
   

3. Add the code below in app.py to load the apps with configuration.

   # app.py
   from django.apps import apps
   from django.conf import settings
   
   apps.populate(settings.INSTALLED_APPS)

Declaring models

1. Indexes (https://docs.djangoproject.com/en/3.0/ref/models/options/#django.db.models.Options.indexes)

   class Meta:
       indexes = [
           models.Index(fields=['username', 'email']),
       ]

2. Model field reference https://docs.djangoproject.com/en/dev/ref/models/fields/

3. Differentiate null=True and blank=True https://stackoverflow.com/questions/8609192/differentiate-null-true-blank-true-in-django

Migration

1. Creating new migrations based on the changes you have made to your models

   python manage.py makemigrations
   

2. Applying and unapplying migrations

   python manage.py migrate
   

3. lists all migrations and their status

   python manage.py showmigrations
   

4. Reversing migrations

   python manage.py migrate <installed_app_name> <migration_file>
   

CRUD

QuerySet API reference : (https://docs.djangoproject.com/en/3.0/ref/models/querysets/) Read more here : (https://books.agiliq.com/projects/django-orm-cookbook/en/latest/)

1. Create

   User(username="helloworld").save()
   User.objects.create(username="helloworld")

2. Read

   # single object
   user = User.objects.get(username="helloworld")
   # multiple object
   users = User.objects.all() # select all users
   users = User.objects.filter() # select all users
   images = Image.objects.filter(user=1, id=1) # select with filter
   images = Image.objects.filter(user=1).exclude(id=1) # select with filter and exclude

   backref => related_name

   # image.py
   class Image(BaseModel):
       user = models.ForeignKey(User, on_delete=models.CASCADE, related_name="images")
   
   # flask shell
   for image in User.objects.get(id=1).images.all():
       print(image.id)

   join => select_related

   donation = Donation.objects.select_related('image__user').get(id=1)
   image = donation.image  # Doesn't hit the database.
   user = image.user   # Doesn't hit the database.

3. Update

   user = User.objects.get(id=1)
   user.username = "new_name"
   user.save()
   # update multiple at once
   Image.objects.filter(user=1).update(user=2) # return number of rows updated

4. Delete

   # delete single object
   User.objects.get(id=1).delete()
   # delete multiple at once
   Image.objects.filter(user=1).delete()

5. Ways to get SQL query

   print(User.filter().query)
   User.filter().query.sql_with_params()
   

Deployment

Add the environment variable below to disable the collectstatic during a deploy.

# .env

DISABLE_COLLECTSTATIC=1