Postgress_conn.md

Connectivity between Django and PostgreSQL

1) Setting up PostgreSQL

Go to the official PostgreSQL website:

• Download PostgreSQL
• Click "Download the Installer" (redirects to EDB website).
• Choose the latest version and your Windows architecture (64-bit recommended).

Run the Installer:

• Open the downloaded .exe file.
• Click Next to proceed with the installation.
• Select Components:
  • Keep the default selection (PostgreSQL Server, pgAdmin, Stack Builder).
  • Click Next.

Choose Installation Directory:

• Select where PostgreSQL will be installed or keep the default location.
• Click Next.

Set a Password for the PostgreSQL User:

• Enter a strong password for the superuser (postgres).
• Remember this password; you’ll need it to log in.
• Click Next.

Choose Port Number:

• Default port is 5432 (keep it unless needed).
• Click Next.

Finish the Installation:

• Click Next → Finish after installation.

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2) Setting up Django

What is Django?

• Python web framework
• Follows Model View Template (MVT) architecture.
• Easy to develop, high security, and high scalability.
• Has ORM (Object Relational Mapping) for database interaction.

What is MVT?

• Similar to MVC (Model View Controller).
  • Model → Defines Database Structure.
  • View → Handles logic.
  • Template → Controls frontend.

Flow of Django and Database:

Request → Django API → Django → Database → Django converts the data into JSON → Django API → User

Why Django?

• Compared to other frameworks (Flask, Tornado, Pyramid), it has:
  • High security.
  • More features.
  • Ability to handle large projects.
  • High scalability.

Django Setup:

• Install Python and pip.
• Create a main folder for the project.
• Create a virtual environment (venv):

  python -m venv env

• Activate the virtual environment:

  env\Scripts\activate  # Windows
  source env/bin/activate  # macOS/Linux

• Install Django:

  pip install Django

• Verify installation:

  django-admin --version

• Create a new Django project:

  django-admin startproject projectname

• Navigate to the project folder and perform initial migrations:

  python manage.py migrate

• Start the server:

  python manage.py runserver

• Check the status using the following URL in the browser:

  http://127.0.0.1:8000/
  

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3) Connectivity between Django and PostgreSQL

Create a Database & User

• Create a user in PostgreSQL:

  CREATE USER username WITH PASSWORD 'your_password';

• Grant user access to the database:

  ALTER ROLE username SET client_encoding TO 'utf8';
  ALTER ROLE username SET default_transaction_isolation TO 'read committed';
  ALTER ROLE username SET timezone TO 'UTC';
  GRANT ALL PRIVILEGES ON DATABASE databasename TO username;

Configure Django Settings

• Open settings.py and update the DATABASES section:

  DATABASES = {
      'default': {
          'ENGINE': 'django.db.backends.postgresql',
          'NAME': 'database_name',
          'USER': 'username',
          'PASSWORD': 'password',
          'HOST': 'localhost',  # If running PostgreSQL locally
          'PORT': '5432',       # Default PostgreSQL port
      }
  }

• Apply migrations:

  python manage.py migrate

• Run the server to verify:

  python manage.py runserver

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4) Django REST API

Install Django REST Framework

pip install djangorestframework

• Check installation:

  python -m django --version

• Add 'rest_framework' to INSTALLED_APPS in settings.py.
• Install psycopg (PostgreSQL adapter for Python):

  pip install psycopg[binary]

• Apply migrations:

  python manage.py migrate

Create a Superuser

python manage.py createsuperuser

Create a Django App for API

python manage.py startapp appname

• Add 'appname' to INSTALLED_APPS in settings.py.

Define Models in models.py

from django.db import models

class Product(models.Model):
    name = models.CharField(max_length=100)
    description = models.TextField()
    price = models.DecimalField(max_digits=10, decimal_places=2)
    stock = models.IntegerField()

    def __str__(self):
        return self.name

• Apply migrations:

  python manage.py makemigrations
  python manage.py migrate

Register Model in admin.py

from django.contrib import admin
from .models import Product
admin.site.register(Product)

Serialize the Model (serializers.py)

from rest_framework import serializers
from .models import Product

class ProductSerializer(serializers.ModelSerializer):
    class Meta:
        model = Product
        fields = '__all__'

Create API Views (views.py)

from rest_framework.decorators import api_view
from rest_framework.response import Response
from rest_framework import status
from .models import Product
from .serializers import ProductSerializer

@api_view(['GET', 'POST'])
def product_list(request):
    if request.method == 'GET':
        products = Product.objects.all()
        serializer = ProductSerializer(products, many=True)
        return Response(serializer.data)
    elif request.method == 'POST':
        serializer = ProductSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

Define URLs (urls.py in appname)

from django.urls import path
from .views import product_list

urlpatterns = [
    path('products/', product_list, name='product-list'),
]

Register API Routes in Project urls.py

from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('api/', include('appname.urls')),  # Include API URLs
]

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Notes

• Adjust file names and paths as per your project structure.
• The API endpoints can be tested using Postman or Django Admin Panel.
• Django REST API helps in building scalable web services efficiently.