Hello World¶

Create your first REROUTE API in just 5 minutes!

What You'll Learn¶

How to create a new REROUTE project
Basic project structure
Your first API endpoint
How to test your API

Prerequisites¶

Python 3.8+ installed
REROUTE installed (pip install reroute[fastapi])
Basic command line knowledge

Watch the Video Demo¶

Visual Learner?

Prefer watching? Here's a 2-minute video showing the complete process:

Download video | Watch on GitHub

Video covers: Project initialization, first API endpoint, and testing with Swagger UI

Step 1: Create a New Project¶

Use the REROUTE CLI to create a new project:

reroute init hello-world --framework fastapi

You'll be prompted with a few questions. Answer "No" to tests and database for now.

The CLI will create your project structure:

hello-world/
├── app/
│   ├── routes/
│   │   └── hello/
│   │       └── page.py
│   ├── root.py
│   └── __init__.py
├── config.py
├── logger.py
├── main.py
├── requirements.txt
├── pyproject.toml
└── .env.example

Step 2: Navigate to Your Project¶

cd hello-world

Step 3: Install Dependencies¶

Using uv (recommended):¶

uv venv
source .venv/bin/activate  # macOS/Linux
# or
.venv\Scripts\activate  # Windows

uv sync

Using pip:¶

python -m venv venv
source venv/bin/activate  # macOS/Linux
# or
venv\Scripts\activate  # Windows

pip install -r requirements.txt

Step 4: Run Your Server¶

python main.py

You should see:

==================================================
REROUTE Server Starting
==================================================
  Framework: FastAPI
  Host: 0.0.0.0
  Port: 7376
  Docs: /docs
==================================================

INFO:     Started server process
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://0.0.0.0:7376

Step 5: Test Your API¶

Open your browser or use curl to test your endpoints:

Root Endpoint¶

curl http://localhost:7376/

Expected Output:

{
  "message": "Welcome to hello-world API",
  "docs": "/docs",
  "health": "/health"
}

Hello Endpoint¶

curl http://localhost:7376/hello

Expected Output:

{
  "message": "Hello, World!"
}

Health Check¶

curl http://localhost:7376/health

Expected Output:

{
  "status": "healthy",
  "service": "hello-world"
}

Step 6: View API Documentation¶

Open your browser and navigate to:

Swagger UI: http://localhost:7376/docs

You'll see interactive API documentation where you can test all your endpoints!

Understanding Your Code¶

main.py¶

from fastapi import FastAPI
from reroute import FastAPIAdapter
from config import AppConfig

app = FastAPI(title="hello-world")
adapter = FastAPIAdapter(
    fastapi_app=app,
    app_dir="./app",
    config=AppConfig
)
adapter.register_routes()

if __name__ == "__main__":
    adapter.run_server()

What's happening: 1. Create a FastAPI app 2. Initialize REROUTE adapter with the app 3. Register all routes from app/routes/ directory 4. Start the server

app/root.py¶

from fastapi import Request
from reroute import RouteBase

class RootRoutes(RouteBase):
    """Root and health check endpoints."""

    def get(self, request: Request):
        """Root endpoint with welcome message."""
        return {
            "message": f"Welcome to {request.app.title} API",
            "docs": "/docs",
            "health": "/health"
        }

def health():
    """Health check endpoint."""
    return {"status": "healthy", "service": "hello-world"}

app/routes/hello/page.py¶

from reroute import RouteBase

class HelloRoutes(RouteBase):
    """Hello World endpoint."""

    def get(self):
        """Return hello message."""
        return {"message": "Hello, World!"}

File-Based Routing¶

REROUTE uses file-based routing inspired by Next.js:

app/routes/
    ├── page.py              → /
    ├── users/
    │   └── page.py          → /users
    └── posts/
        ├── page.py          → /posts
        └── [id]/
            └── page.py      → /posts/{id}

Key concepts: - page.py files become routes - Folder names become URL paths - Class methods (get, post, etc.) handle HTTP methods

Troubleshooting¶

Port Already in Use¶

Error: OSError: [Errno 48] Address already in use

Solution: 1. Change port in config.py: PORT = 8080 2. Or kill the process using port 7376

Module Not Found¶

Error: ModuleNotFoundError: No module named 'fastapi'

Solution:

pip install -r requirements.txt

Routes Not Working¶

Check: 1. File is named page.py (not routes.py or other) 2. Class inherits from RouteBase 3. At least one HTTP method defined (get, post, etc.)

Next Steps¶

Congratulations! You've created your first REROUTE API!

What's next: - First Server - Learn more about running the server - Understanding Routes - Deep dive into file-based routing - Dynamic Routes - Work with path parameters

Summary¶

In just 5 minutes, you: - Created a new REROUTE project - Understood the basic project structure - Ran your development server - Tested your API endpoints - Viewed interactive API documentation

Key takeaways: - REROUTE uses file-based routing - page.py files become API endpoints - Class methods handle HTTP methods - Swagger UI documentation is automatic

Ready to learn more? Continue to First Server!