💰 Smart Expense Tracker REST API

A RESTful expense management API built with FastAPI that allows users to create, view, filter, summarize, and delete personal expense records. The project demonstrates REST API design, request validation, modular backend architecture, JSON-based data persistence, and automated testing.

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🌐 Live Demo

• Live API: https://smart-expense-tracker-mpo7.onrender.com
• Swagger UI: https://smart-expense-tracker-mpo7.onrender.com/docs

🚀 Features

• ✅ Add a new expense
• ✅ View all expenses
• ✅ Filter expenses by category
• ✅ Calculate total expenses
• ✅ Calculate category-wise expense totals
• ✅ Delete an expense
• ✅ Automatic request validation using Pydantic
• ✅ Interactive Swagger/OpenAPI documentation
• ✅ Automated API testing using Pytest

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🏗️ System Architecture

                    Client
                       │
                HTTP Requests
                       │
               FastAPI Application
                       │
                  APIRouter
                       │
        ┌──────────────┴──────────────┐
        │                             │
 Request Validation            Storage Layer
   (Pydantic)                     (JSON)
        │                             │
        └──────────────┬──────────────┘
                       │
                 expenses.json

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🛠️ Technology Stack

• Python 3
• FastAPI
• Pydantic
• Pytest
• Uvicorn
• JSON (Local Storage)

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📁 Project Structure

smart-expense-tracker/
│
├── README.md
├── AI_NOTES.md
├── requirements.txt
├── pytest.ini
├── .gitignore
│
├── src/
│   ├── __init__.py
│   ├── main.py
│   ├── routes.py
│   ├── models.py
│   ├── storage.py
│   └── expenses.json
│
└── tests/
    └── test_api.py

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⚙️ Installation

Clone the repository:

git clone https://github.com/DecodingAzero/smart-expense-tracker.git
cd smart-expense-tracker

Install the required dependencies:

pip install -r requirements.txt

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▶️ Running the Application

Start the FastAPI development server:

uvicorn src.main:app --reload

The application will be available at:

http://127.0.0.1:8000

Interactive API documentation (Swagger UI):

http://127.0.0.1:8000/docs

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🧪 Running the Tests

Execute the automated test suite:

pytest

All API endpoints and request validation are covered by automated tests.

Test Results

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📚 API Endpoints

Method	Endpoint	Description
GET	/	Welcome endpoint
POST	/expenses	Create a new expense
GET	/expenses	Retrieve all expenses
GET	/expenses?category=Food	Filter expenses by category
GET	/expenses/total	Calculate total expenses
GET	/expenses/total?category=Food	Calculate category-wise totals
DELETE	/expenses/{expense_id}	Delete an expense

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📖 API Documentation

FastAPI automatically generates interactive API documentation using Swagger UI and OpenAPI.

After starting the server, visit:

http://127.0.0.1:8000/docs

The Swagger interface allows you to explore and test every endpoint directly from your browser.

Swagger UI

🔍 Testing

The project includes automated tests covering:

• API availability
• Creating expenses
• Retrieving expenses
• Filtering by category
• Calculating totals
• Deleting expenses
• Request validation

Consider adding a screenshot of the successful pytest output to showcase the passing test suite.

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🚀 Future Improvements

Potential enhancements for future versions include:

• PostgreSQL or SQLite database integration
• User authentication with JWT
• Expense update endpoint (PUT/PATCH)
• Pagination and sorting
• Monthly expense analytics
• Docker support
• Cloud deployment (Render/Railway)
• CI/CD using GitHub Actions

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🤖 AI Assistance

AI was used as a development and learning assistant throughout this project. Details about AI-assisted development, code verification, and design decisions are documented in AI_NOTES.md.

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📄 License

This project is intended for educational and portfolio purposes.