Day 14 — User Course API

A REST API built with FastAPI and SQLAlchemy demonstrating One-to-Many database relationships. A User can own many Courses. Built as part of a 60-day Python learning streak.

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Features

• Create users and courses
• One-to-Many relationship between User and Course
• Nested response — fetching a user returns their courses automatically
• Cascade delete — deleting a user removes all their courses
• Input validation with Pydantic v2
• Eager loading with joinedload for optimised queries

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Project Structure

day14-user-course-api/
├── database.py     # SQLite engine, SessionLocal, Base
├── models.py       # User and Course ORM models with relationship
├── schemas.py      # Pydantic schemas including nested UserOut
└── main.py         # FastAPI app with all endpoints

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Tech Stack

• Python 3.11+
• FastAPI
• SQLAlchemy
• SQLite
• Pydantic v2
• Uvicorn

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Setup & Run

# Clone the repo
git clone https://github.com/studyhaxer/day14-user-course-api.git
cd day14-user-course-api

# Install dependencies
pip install fastapi sqlalchemy uvicorn

# Run the server
uvicorn main:app --reload

Open http://127.0.0.1:8000/docs to explore the API via Swagger UI.

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API Endpoints

Method	Endpoint	Description
POST	/users	Create a new user
GET	/users	List all users
GET	/users/{id}	Get user with nested courses
POST	/users/{id}/courses	Add a course to a user
DELETE	/users/{id}	Delete user and all their courses

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Key Concepts Practised

• ForeignKey linking Course to User
• relationship() with back_populates for bidirectional access
• cascade="all, delete-orphan" for automatic child deletion
• joinedload() for eager loading related records
• Nested Pydantic schemas (List[CourseOut] inside UserOut)
• from_attributes = True for ORM object serialisation

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Example Request

Create a user:

POST /users
{
  "name": "Ati",
  "email": "ati@example.com"
}

Add a course to user with id=1:

POST /users/1/courses
{
  "title": "FastAPI Mastery"
}

Get user with all courses:

GET /users/1

{
  "id": 1,
  "name": "Ati",
  "email": "ati@example.com",
  "courses": [
    { "id": 1, "title": "FastAPI Mastery" }
  ]
}

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Part of the Python Learning Streak

This project is Day 14 of a structured 60-day Python → FastAPI → AI Platform journey.

Author

Hafiz Atta ur Rahman (Ati)
M.Phil CS — Gold Medalist · Senior Subject Expert, Punjab Education Department
Founder, Umar Science Academy Chunian
GitHub: @studyhaxer