RouteLit FastAPI Adapter¶

A FastAPI adapter for the RouteLit framework, enabling seamless integration of RouteLit's reactive UI components with FastAPI web applications.

Installation¶

pip install routelit routelit-fastapi

Quick Start¶

Here's a complete example to get you started:

from fastapi import FastAPI, Request
import uvicorn
from routelit import RouteLit, RouteLitBuilder
from routelit_fastapi import RouteLitFastAPIAdapter

# Create FastAPI app
app = FastAPI()

# Create RouteLit instance
routelit = RouteLit()

# Create and configure the adapter
adapter = RouteLitFastAPIAdapter(routelit).configure(app)

# Define your view function
def build_hello_view(rl: RouteLitBuilder):
    name = rl.text_input(label="What is your name", placeholder="John", default_value="")
    rl.write(f"Hello {name}")
    if rl.button("Submit"):
        rl.write("Thanks for your submission!")

# Option 1: Traditional approach with explicit route registration
@app.api_route("/", methods=["GET", "POST"])
async def hello(request: Request):
    return await adapter.response(build_hello_view, request)

# Option 2: Simplified decorator approach (recommended)
@adapter.route("/")
def hello_view(rl: RouteLitBuilder):
    name = rl.text_input(label="What is your name", placeholder="John", default_value="")
    rl.write(f"Hello {name}")
    if rl.button("Submit"):
        rl.write("Thanks for your submission!")

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000)

Features¶

Framework Agnostic: Works seamlessly with FastAPI
Declarative UI: Build interfaces using simple Python functions with a builder pattern
Interactive Components: Buttons, forms, inputs, selects, checkboxes, containers, columns, etc.
State Management: Built-in session state management with cookie-based sessions
Reactive Updates: Automatic UI updates based on user interactions
HTTP Streaming: Support for streaming responses using JSONL
Development Mode: Hot reloading support for frontend development

Usage¶

Basic Route Registration¶

You can register routes in two ways:

Option 1: Traditional Approach

@app.api_route("/counter", methods=["GET", "POST"])
async def counter(request: Request):
    return await adapter.response(build_counter_view, request)

Option 2: Simplified Decorator (Recommended)

@adapter.route("/counter")
def counter_view(rl: RouteLitBuilder):
    if "counter" not in rl.session_state:
        rl.session_state["counter"] = 0

    counter = rl.session_state["counter"]
    rl.markdown(f"## Count: {counter}")

    if rl.button("Increment", key="inc"):
        rl.session_state["counter"] = counter + 1
        rl.rerun()

Streaming Routes¶

For HTTP streaming responses using JSONL:

# Traditional approach
@app.api_route("/stream", methods=["GET", "POST"])
async def stream_endpoint(request: Request):
    return await adapter.stream_response(build_stream_view, request)

# Simplified decorator (recommended)
@adapter.stream_route("/stream")
async def stream_view(rl: RouteLitBuilder):
    for i in range(10):
        rl.text(f"Count: {i}")

Development Mode¶

For development with hot reloading of the frontend:

adapter = RouteLitFastAPIAdapter(
    routelit,
    run_mode="dev_client",
    local_frontend_server="http://localhost:5173"
).configure(app)

Configuration Options¶

When creating the adapter, you can configure the following options:

Parameter	Type	Default	Description
`static_path`	`str \\| None`	Auto-detected	Custom path for static assets
`template_path`	`str`	Auto-detected	Custom path for templates
`run_mode`	`str`	`"prod"`	One of `"prod"`, `"dev_client"`, `"dev_components"`
`local_frontend_server`	`str \\| None`	`None`	URL of local Vite dev server (for dev mode)
`local_components_server`	`str \\| None`	`None`	URL of local components dev server (for dev mode)
`cookie_config`	`CookieConfig \\| None`	Production defaults	Custom cookie configuration

Run Modes¶

prod: Production mode with secure cookie settings
dev_client: Development mode for the client with hot reloading
dev_components: Development mode for the components

In production mode, the default cookie configuration is:

{
    "secure": True,
    "samesite": "none",
    "httponly": True,
    "max_age": 60 * 60 * 24 * 1,  # 1 day
}

You can override these settings:

adapter = RouteLitFastAPIAdapter(
    routelit,
    cookie_config={
        "secure": False,
        "max_age": 3600,  # 1 hour
    }
).configure(app)

API Reference¶

For detailed API documentation, see the Modules page.

Example Application¶

Check out the example application in the repository for a complete working example with:

Counter example using standard responses
Streaming counter example with real-time updates
Multiple route patterns

License¶

Apache-2.0 License

Maintainer¶

Maintained by @rolangom.