Routing

The Chalice.route() method is used to construct which routes you want to create for your API. The concept is the same mechanism used by Flask and bottle. You decorate a function with @app.route(...), and whenever a user requests that URL, the function you’ve decorated is called. For example, suppose you deployed this app:

from chalice import Chalice

app = Chalice(app_name='helloworld')


@app.route('/')
def index():
    return {'view': 'index'}

@app.route('/a')
def a():
    return {'view': 'a'}

@app.route('/b')
def b():
    return {'view': 'b'}

If you go to https://endpoint/, the index() function would be called. If you went to https://endpoint/a and https://endpoint/b, then the a() and b() function would be called, respectively.

Note

Do not end your route paths with a trailing slash. If you do this, the chalice deploy command will raise a validation error.

You can also create a route that captures part of the URL. This captured value will then be passed in as arguments to your view function:

from chalice import Chalice

app = Chalice(app_name='helloworld')


@app.route('/users/{name}')
def users(name):
    return {'name': name}

If you then go to https://endpoint/users/james, then the view function will be called as: users('james'). The parameters are passed as keyword parameters based on the name as they appear in the URL. The argument names for the view function must match the name of the captured argument:

from chalice import Chalice

app = Chalice(app_name='helloworld')


@app.route('/a/{first}/b/{second}')
def users(first, second):
    return {'first': first, 'second': second}

Other Request Metadata

The route path can only contain [a-zA-Z0-9._-] chars and curly braces for parts of the URL you want to capture. You do not need to model other parts of the request you want to capture, including headers and query strings. Within a view function, you can introspect the current request using the app.current_request attribute. This also means you cannot control the routing based on query strings or headers. Here’s an example for accessing query string data in a view function:

from chalice import Chalice

app = Chalice(app_name='helloworld')


@app.route('/users/{name}')
def users(name):
    result = {'name': name}
    if app.current_request.query_params.get('include-greeting') == 'true':
        result['greeting'] = 'Hello, %s' % name
    return result

In the function above, if the user provides a ?include-greeting=true in the HTTP request, then an additional greeting key will be returned:

$ http https://endpoint/api/users/bob

{
    "name": "bob"
}

$ http https://endpoint/api/users/bob?include-greeting=true

{
    "greeting": "Hello, bob",
    "name": "bob"
}
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