starlette/docs/routing.md

Starlette includes a Router class which is an ASGI application that dispatches incoming requests to endpoints or submounted applications.

from starlette.routing import Mount, Route, Router
from myproject import Homepage, SubMountedApp


app = Router([
    Route('/', endpoint=Homepage, methods=['GET']),
    Mount('/mount', app=SubMountedApp)
])

Paths can use URI templating style to capture path components.

Route('/users/{username}', endpoint=User, methods=['GET'])

Convertors for int, float, and path are also available:

Route('/users/{user_id:int}', endpoint=User, methods=['GET'])

Path parameters are made available in the request, as the request.path_params dictionary.

Because the target of a Mount is an ASGI instance itself, routers allow for easy composition. For example:

app = Router([
    Route('/', endpoint=Homepage, methods=['GET']),
    Mount('/users', app=Router([
        Route('/', endpoint=Users, methods=['GET', 'POST']),
        Route('/{username}', endpoint=User, methods=['GET']),
    ]))
])

The router will respond with "404 Not found" or "405 Method not allowed" responses for requests which do not match.

Incoming paths are matched against each Route in order.

If you need to have a Route with a fixed path that would also match a Route with parameters you should add the Route with the fixed path first.

For example, with an additional Route like:

Route('/users/me', endpoint=UserMe, methods=['GET'])

You should add that route for /users/me before the one for /users/{username}:

app = Router([
    Route('/users/me', endpoint=UserMe, methods=['GET']),
    Route('/users/{username}', endpoint=User, methods=['GET']),
])