This backend powers a simple product selling website using:

• FastAPI — high-performance Python web framework

• Uvicorn — ASGI server to run the app

• SQLModel — modern ORM combining SQLAlchemy + Pydantic

• PostgreSQL — as the database

• psycopg2-binary — PostgreSQL database adapter

• python-dotenv — to manage environment variables

bash

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product_site/
└── backend/
    ├── env/             # Python virtual environment
    ├── .env             # Environment variables
    ├── main.py          # FastAPI application
    └── models.py        # SQLModel models

Create the project directories:

bash

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mkdir -p product_site/backend
cd product_site/backend

Create a Python virtual environment:

bash

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python3 -m venv env
source env/bin/activate

Install required dependencies via pip:

php

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pip install fastapi uvicorn sqlmodel psycopg2-binary python-multipart python-dotenv

Create a .env file to store your database connection string:

bash

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DATABASE_URL=postgresql+psycopg2://shop_admin:secure_password@localhost/product_store

Access PostgreSQL:

nginx

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sudo -u postgres psql

Inside the prompt:

pgsql

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CREATE USER shop_admin WITH PASSWORD 'secure_password';
CREATE DATABASE product_store OWNER shop_admin;
GRANT ALL PRIVILEGES ON DATABASE product_store TO shop_admin;
\q

Example product table structure:

Check table structure:

nginx

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sudo -u postgres psql product_store
\d product;

models.py — defines the Product model using SQLModel.
main.py — contains FastAPI app, routes, and database session management.

A Session is a temporary connection to the database that lets you:

• Perform SQL queries

• Add, delete, or update records

• Control transactions

Each API route gets its own session. Sessions must be opened, used, and closed properly to avoid database connection issues.

Use Uvicorn to serve the FastAPI app:

css

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uvicorn main:app --reload

Open:

arduino

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http://127.0.0.1:8000/docs

Use Swagger UI to test:

• GET /products/ — List all products

• POST /products/ — Add a product

• FastAPI + Uvicorn set up for backend API

• SQLModel integrated with PostgreSQL via psycopg2

• Database connection string secured using .env

• PostgreSQL database and product table configured

• API endpoints operational and testable via Swagger UI

• Add .env to .gitignore to avoid exposing credentials.

• Use --reload flag with Uvicorn during development only.

• Swagger UI is automatically generated at /docs.

• SQLModel uses Pydantic models for validation and SQLAlchemy ORM under the hood.