python

Python App Sample

Prerequisites

Refer to the README doc for preparation.

Quick Start

1. Install Dependencies

Using uv (recommended):

Linux/macOS:

# Install uv if you haven't already
curl -LsSf https://astral.sh/uv/install.sh | sh

# Navigate to the python directory
cd complete/python

# Install dependencies from pyproject.toml
uv sync

Windows (PowerShell):

# Install uv if you haven't already
powershell -c "irm https://astral.sh/uv/install.ps1 | iex"

# Navigate to the python directory
cd python

# Install dependencies from pyproject.toml
uv sync

Using pip:

Linux/macOS:

# Create virtual environment
python -m venv .venv
source .venv/bin/activate

# Install dependencies
pip install fastapi uvicorn sqlalchemy

Windows (Command Prompt):

# Create virtual environment
python -m venv .venv
.venv\Scripts\activate

# Install dependencies
pip install fastapi uvicorn sqlalchemy

Windows (PowerShell):

# Create virtual environment
python -m venv .venv
.venv\Scripts\Activate.ps1

# Install dependencies
pip install fastapi uvicorn sqlalchemy

2. Run the Application

Create a database

Linux/macOS:

touch sns_api.db

Windows (PowerShell):

New-Item -Name sns_api.db -Force

Using uv:

# Start the development server
uv run uvicorn main:app --host 0.0.0.0 --port 8000 --reload

Using pip:

Linux/macOS:

# Ensure virtual environment is activated
source .venv/bin/activate

# Start the development server
uvicorn main:app --host 0.0.0.0 --port 8000 --reload

Windows (Command Prompt):

# Ensure virtual environment is activated
.venv\Scripts\activate

# Start the development server
uvicorn main:app --host 0.0.0.0 --port 8000 --reload

Windows (PowerShell):

# Ensure virtual environment is activated
.venv\Scripts\Activate.ps1

# Start the development server
uvicorn main:app --host 0.0.0.0 --port 8000 --reload

The API will be available at: http://localhost:8000

3. Access Documentation

• Swagger UI: http://localhost:8000/docs
• OpenAPI JSON: http://localhost:8000/openapi.json

API Endpoints

Posts

• GET /api/posts - List all posts
• POST /api/posts - Create a new post
• GET /api/posts/{postId} - Get a specific post
• PATCH /api/posts/{postId} - Update a post
• DELETE /api/posts/{postId} - Delete a post

Comments

• GET /api/posts/{postId}/comments - List comments for a post
• POST /api/posts/{postId}/comments - Create a comment
• GET /api/posts/{postId}/comments/{commentId} - Get a specific comment
• PATCH /api/posts/{postId}/comments/{commentId} - Update a comment
• DELETE /api/posts/{postId}/comments/{commentId} - Delete a comment

Likes

• POST /api/posts/{postId}/likes - Like a post
• DELETE /api/posts/{postId}/likes - Unlike a post

Example Usage

Create a Post

Linux/macOS/Windows (Git Bash):

curl -X POST "http://localhost:8000/api/posts" \
  -H "Content-Type: application/json" \
  -d '{
    "username": "john_doe",
    "content": "Hello, world! This is my first post."
  }'

Windows (PowerShell):

Invoke-RestMethod -Uri "http://localhost:8000/api/posts" -Method POST `
  -ContentType "application/json" `
  -Body '{"username": "john_doe", "content": "Hello, world! This is my first post."}'

Windows (Command Prompt):

curl -X POST "http://localhost:8000/api/posts" ^
  -H "Content-Type: application/json" ^
  -d "{\"username\": \"john_doe\", \"content\": \"Hello, world! This is my first post.\"}"

Get All Posts

Linux/macOS/Windows (Git Bash):

curl -X GET "http://localhost:8000/api/posts"

Windows (PowerShell):

Invoke-RestMethod -Uri "http://localhost:8000/api/posts" -Method GET

Windows (Command Prompt):

curl -X GET "http://localhost:8000/api/posts"

Add a Comment

Linux/macOS/Windows (Git Bash):

curl -X POST "http://localhost:8000/api/posts/{postId}/comments" \
  -H "Content-Type: application/json" \
  -d '{
    "username": "jane_smith",
    "content": "Great post!"
  }'

Windows (PowerShell):

Invoke-RestMethod -Uri "http://localhost:8000/api/posts/{postId}/comments" -Method POST `
  -ContentType "application/json" `
  -Body '{"username": "jane_smith", "content": "Great post!"}'

Like a Post

Linux/macOS/Windows (Git Bash):

curl -X POST "http://localhost:8000/api/posts/{postId}/likes" \
  -H "Content-Type: application/json" \
  -d '{
    "username": "jane_smith"
  }'

Windows (PowerShell):

Invoke-RestMethod -Uri "http://localhost:8000/api/posts/{postId}/likes" -Method POST `
  -ContentType "application/json" `
  -Body '{"username": "jane_smith"}'

Project Structure

python/
├── main.py              # FastAPI application entry point
├── pyproject.toml       # Project dependencies and configuration
├── README.md           # This file
├── sns_api.db          # SQLite database (created on first run)
└── .venv/              # Virtual environment (if using pip)

Database

The application uses SQLite for data persistence with the following models:

• Posts: Store user posts with username, content, and timestamps
• Comments: Store comments linked to posts with relationships
• Likes: Track user likes on posts with timestamp information

The database is automatically created on application startup with all necessary tables.

Development

Running Tests

With uv:

# Install test dependencies (if added)
uv add pytest httpx

# Run tests
uv run pytest

With pip (after activating virtual environment):

# Install test dependencies
pip install pytest httpx

# Run tests
pytest

Code Quality

The codebase follows Python best practices:

• Type hints for all functions
• Pydantic models for data validation
• SQLAlchemy for database operations
• FastAPI dependency injection for database sessions

Deployment

Production Setup

For production deployment:

Linux/macOS:

export DATABASE_URL="sqlite:///./sns_api.db"
export HOST="0.0.0.0"
export PORT="8000"

# Run with production settings
uvicorn main:app --host 0.0.0.0 --port 8000

Windows (Command Prompt):

set DATABASE_URL=sqlite:///./sns_api.db
set HOST=0.0.0.0
set PORT=8000

# Run with production settings
uvicorn main:app --host 0.0.0.0 --port 8000

Windows (PowerShell):

$env:DATABASE_URL="sqlite:///./sns_api.db"
$env:HOST="0.0.0.0"
$env:PORT="8000"

# Run with production settings
uvicorn main:app --host 0.0.0.0 --port 8000

Docker (Optional)

FROM python:3.12-slim

WORKDIR /app
COPY pyproject.toml uv.lock ./
RUN pip install uv && uv sync --frozen

COPY main.py ./
EXPOSE 8000

CMD ["uv", "run", "uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

Troubleshooting

Common Issues

1. Port already in use: If port 8000 is busy, use a different port:

   All platforms:

   uvicorn main:app --host 0.0.0.0 --port 8001 --reload

2. Database permission errors: Ensure write permissions in the project directory

3. Import errors: Make sure virtual environment is activated and dependencies are installed

4. Virtual environment activation issues on Windows:

   • If PowerShell execution policy prevents script execution, run:

   Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

   • Alternative: Use Command Prompt instead of PowerShell

5. curl not found on Windows:

   • Install curl from https://curl.se/windows/
   • Or use PowerShell's Invoke-RestMethod as shown in examples
   • Or install Git Bash which includes curl

Logs

Enable detailed logging by setting echo=True in the database engine configuration in main.py.