Python ORMs

• Django ORM
• SQLAlchemy ORM

Django is a high-level Python web framework that encourages rapid development and clean, pragmatic design.

CRUD operations with Django ORM

Learn how to establish a connection to YugabyteDB database and begin basic CRUD operations using the steps in the Build an application page under the Quick start section.

The following sections demonstrate how to perform common tasks required for Python application development using the Django ORM.

Add the Dependencies

To download the Django Rest Framework to your project, run the following command:

pip3 install djangorestframework

In addition, install the YB backend for Django by following the steps in the README. This backend has specific changes with respect to features either not supported by YugabyteDB or supported differently than PostgreSQL. For more information on these features, visit this GitHub issue.

Install the psycopg2 dependency by running the following command:

pip3 install psycopg2

Implement ORM mapping for YugabyteDB

Once all the dependencies are installed, start a Django project and create a new application. To start the project, run the following command:

django-admin startproject yugabyteTest && cd yugabyteTest/

Set up a new Django application using the following command:

python manage.py startapp testdb

After creating the application, configure it to connect to the database. To do this, change the application settings to provide the database credentials. In the file yugabyteTest/settings.py add the following code:

DATABASES = {
    'default': {
        'ENGINE': 'yb_backend',
        'NAME': 'yugabyte',
        'HOST': 'localhost',
        'PORT': 5433,
        'USER': 'yugabyte',
        'CONN_MAX_AGE': None,
        'PASSWORD': 'yugabyte'
    }
}

For better performance with YugabyteDB, use persistent connections (set CONN_MAX_AGE).

You also need the application and rest framework in the INSTALLED_APPS field. Replace the existing code with the following:

INSTALLED_APPS = [
    'rest_framework',
    'testdb.apps.TestdbConfig',
    'django.contrib.contenttypes',
    'django.contrib.auth',
]

REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': [],
    'DEFAULT_PERMISSION_CLASSES': [],
    'UNAUTHENTICATED_USER': None,
}

The next step is to create a model for the table. The table name is users and contains four columns -user_id,firstName,lastName, and email.

Add the following code to testdb/models.py:

rom django.db import models

class Users(models.Model):
    userId = models.AutoField(db_column='user_id', primary_key=True, serialize=False)
    firstName = models.CharField(max_length=50, db_column='first_name')
    lastName = models.CharField(max_length=50, db_column='last_name')
    email = models.CharField(max_length=100, db_column='user_email')

    class Meta:
        db_table = "users"

    def __str__(self):
        return '%d %s %s %s' % (self.userId, self.firstName, self.lastName, self.email)

After creating the model, you need to create a Serializer. Serializers allow complex data such as querysets and model instances to be converted to native Python datatypes, which can then be rendered into JSON, XML, or other content types. Serializers also provide deserialization, allowing parsed data to be converted back into complex types, after first validating the incoming data.

Copy the following code into testdb\serializers.py:

from rest_framework import serializers, status
from testdb.models import Users
from django.core.exceptions import ValidationError

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = Users
        fields = ('userId', 'firstName', 'lastName', 'email')

To finish all the elements of the application, create a ViewSet. In testdb/views.py, add the following:

from django.shortcuts import render
from testdb.models import Users
from rest_framework import viewsets
from testdb.serializers import UserSerializer

class UserViewSet(viewsets.ModelViewSet):
    queryset = Users.objects.all()
    serializer_class = UserSerializer

Finally map the URLs in yugabyteTest/urls.py by adding the following code:

from django.urls import include, re_path
from rest_framework import routers
from testdb.views import UserViewSet

router = routers.SimpleRouter(trailing_slash=False)
router.register(r'users', UserViewSet)
urlpatterns = [
    re_path(r'^', include(router.urls))
]

For Django versions earlier than 4.0, use the following code instead, as you can import the URLs using django.conf.urls:

from django.urls import path, include
from django.conf.urls import url, include
from rest_framework import routers
from testdb.views import UserViewSet

router = routers.SimpleRouter(trailing_slash=False)
router.register(r'users', UserViewSet)

urlpatterns = [
    url(r'^', include(router.urls))
]

This completes the configuration of your test application. The next steps create the migration files and apply the migrations to the database. To do this, run the following command:

python3 manage.py makemigrations
python3 manage.py migrate

A users table should be created in your database. Use the ysqlsh client shell to verify that the users table has been created.

Run the application

To run the application and insert a new row, execute the following steps.

1. Run the Django project using the following command:

   python3 manage.py runserver 8080
   

2. Insert a row using the following command:

   curl --data '{ "firstName" : "John", "lastName" : "Smith", "email" : "[email protected]" }' \
         -v -X POST -H 'Content-Type:application/json' http://localhost:8080/users
   

3. Verify that the new row is inserted by executing the following command:

   curl http://localhost:8080/users
   

You should see the following output:

[{"userId":1,"firstName":"John","lastName":"Smith","email":"[email protected]"}]

You can also verify this using the ysqlsh client shell.

Next steps

• Explore Scaling Python Applications with YugabyteDB.
• Learn how to develop Python applications with YugabyteDB Managed.