If you haven’t done so already, please take a moment to install the Falcon web framework before continuing.

Learning by Example

Here is a simple example from Falcon’s README, showing how to get started writing an app.

# examples/things.py

# Let's get this party started!
from wsgiref.simple_server import make_server

import falcon

# Falcon follows the REST architectural style, meaning (among
# other things) that you think in terms of resources and state
# transitions, which map to HTTP verbs.
class ThingsResource:
    def on_get(self, req, resp):
        """Handles GET requests"""
        resp.status = falcon.HTTP_200  # This is the default status
        resp.content_type = falcon.MEDIA_TEXT  # Default is JSON, so override
        resp.text = (
            '\nTwo things awe me most, the starry sky '
            'above me and the moral law within me.\n'
            '    ~ Immanuel Kant\n\n'

# falcon.App instances are callable WSGI apps
# in larger applications the app is created in a separate file
app = falcon.App()

# Resources are represented by long-lived class instances
things = ThingsResource()

# things will handle all requests to the '/things' URL path
app.add_route('/things', things)

if __name__ == '__main__':
    with make_server('', 8000, app) as httpd:
        print('Serving on port 8000...')

        # Serve until process is killed

You can run the above example directly using the included wsgiref server:

$ pip install falcon
$ python things.py

Then, in another terminal:

$ curl localhost:8000/things

As an alternative to Curl, you might want to give HTTPie a try:

$ pip install --upgrade httpie
$ http localhost:8000/things

A More Complex Example

Here is a more involved example that demonstrates reading headers and query parameters, handling errors, and working with request and response bodies.

Note that this example assumes that the requests package has been installed.

# examples/things_advanced.py

import json
import logging
import uuid
from wsgiref import simple_server

import falcon
import requests

class StorageEngine:
    def get_things(self, marker, limit):
        return [{'id': str(uuid.uuid4()), 'color': 'green'}]

    def add_thing(self, thing):
        thing['id'] = str(uuid.uuid4())
        return thing

class StorageError(Exception):
    def handle(ex, req, resp, params):
        # TODO: Log the error, clean up, etc. before raising
        raise falcon.HTTPInternalServerError()

class SinkAdapter:

    engines = {
        'ddg': 'https://duckduckgo.com',
        'y': 'https://search.yahoo.com/search',

    def __call__(self, req, resp, engine):
        url = self.engines[engine]
        params = {'q': req.get_param('q', True)}
        result = requests.get(url, params=params)

        resp.status = falcon.code_to_http_status(result.status_code)
        resp.content_type = result.headers['content-type']
        resp.text = result.text

class AuthMiddleware:
    def process_request(self, req, resp):
        token = req.get_header('Authorization')
        account_id = req.get_header('Account-ID')

        challenges = ['Token type="Fernet"']

        if token is None:
            description = 'Please provide an auth token as part of the request.'

            raise falcon.HTTPUnauthorized(
                title='Auth token required',

        if not self._token_is_valid(token, account_id):
            description = (
                'The provided auth token is not valid. '
                'Please request a new token and try again.'

            raise falcon.HTTPUnauthorized(
                title='Authentication required',

    def _token_is_valid(self, token, account_id):
        return True  # Suuuuuure it's valid...

class RequireJSON:
    def process_request(self, req, resp):
        if not req.client_accepts_json:
            raise falcon.HTTPNotAcceptable(
                description='This API only supports responses encoded as JSON.',

        if req.method in ('POST', 'PUT'):
            if 'application/json' not in req.content_type:
                raise falcon.HTTPUnsupportedMediaType(
                    title='This API only supports requests encoded as JSON.',

class JSONTranslator:
    # NOTE: Normally you would simply use req.media and resp.media for
    # this particular use case; this example serves only to illustrate
    # what is possible.

    def process_request(self, req, resp):
        # req.stream corresponds to the WSGI wsgi.input environ variable,
        # and allows you to read bytes from the request body.
        # See also: PEP 3333
        if req.content_length in (None, 0):
            # Nothing to do

        body = req.stream.read()
        if not body:
            raise falcon.HTTPBadRequest(
                title='Empty request body',
                description='A valid JSON document is required.',

            req.context.doc = json.loads(body.decode('utf-8'))

        except (ValueError, UnicodeDecodeError):
            description = (
                'Could not decode the request body. The '
                'JSON was incorrect or not encoded as '

            raise falcon.HTTPBadRequest(title='Malformed JSON', description=description)

    def process_response(self, req, resp, resource, req_succeeded):
        if not hasattr(resp.context, 'result'):

        resp.text = json.dumps(resp.context.result)

def max_body(limit):
    def hook(req, resp, resource, params):
        length = req.content_length
        if length is not None and length > limit:
            msg = (
                'The size of the request is too large. The body must not '
                'exceed ' + str(limit) + ' bytes in length.'

            raise falcon.HTTPPayloadTooLarge(
                title='Request body is too large', description=msg

    return hook

class ThingsResource:
    def __init__(self, db):
        self.db = db
        self.logger = logging.getLogger('thingsapp.' + __name__)

    def on_get(self, req, resp, user_id):
        marker = req.get_param('marker') or ''
        limit = req.get_param_as_int('limit') or 50

            result = self.db.get_things(marker, limit)
        except Exception as ex:

            description = (
                'Aliens have attacked our base! We will '
                'be back as soon as we fight them off. '
                'We appreciate your patience.'

            raise falcon.HTTPServiceUnavailable(
                title='Service Outage', description=description, retry_after=30

        # NOTE: Normally you would use resp.media for this sort of thing;
        # this example serves only to demonstrate how the context can be
        # used to pass arbitrary values between middleware components,
        # hooks, and resources.
        resp.context.result = result

        resp.set_header('Powered-By', 'Falcon')
        resp.status = falcon.HTTP_200

    @falcon.before(max_body(64 * 1024))
    def on_post(self, req, resp, user_id):
            doc = req.context.doc
        except AttributeError:
            raise falcon.HTTPBadRequest(
                title='Missing thing',
                description='A thing must be submitted in the request body.',

        proper_thing = self.db.add_thing(doc)

        resp.status = falcon.HTTP_201
        resp.location = '/%s/things/%s' % (user_id, proper_thing['id'])

# Configure your WSGI server to load "things.app" (app is a WSGI callable)
app = falcon.App(

db = StorageEngine()
things = ThingsResource(db)
app.add_route('/{user_id}/things', things)

# If a responder ever raises an instance of StorageError, pass control to
# the given handler.
app.add_error_handler(StorageError, StorageError.handle)

# Proxy some things to another service; this example shows how you might
# send parts of an API off to a legacy system that hasn't been upgraded
# yet, or perhaps is a single cluster that all data centers have to share.
sink = SinkAdapter()
app.add_sink(sink, r'/search/(?P<engine>ddg|y)\Z')

# Useful for debugging problems in your API; works with pdb.set_trace(). You
# can also use Gunicorn to host your app. Gunicorn can be configured to
# auto-restart workers when it detects a code change, and it also works
# with pdb.
if __name__ == '__main__':
    httpd = simple_server.make_server('', 8000, app)

Again this code uses wsgiref, but you can also run the above example using any WSGI server, such as uWSGI or Gunicorn. For example:

$ pip install requests gunicorn
$ gunicorn things:app

On Windows you can run Gunicorn and uWSGI via WSL, or you might try Waitress:

$ pip install requests waitress
$ waitress-serve --port=8000 things:app

To test this example go to the another terminal and run:

$ http localhost:8000/1/things authorization:custom-token

To visualize the application configuration the Inspect Module can be used:

falcon-inspect-app things_advanced:app

This would print for this example application:

Falcon App (WSGI)
• Routes:
    ⇒ /{user_id}/things - ThingsResource:
       ├── GET - on_get
       └── POST - on_post
• Middleware (Middleware are independent):
    → AuthMiddleware.process_request
      → RequireJSON.process_request
        → JSONTranslator.process_request

            ├── Process route responder

        ↢ JSONTranslator.process_response
• Sinks:
    ⇥ /search/(?P<engine>ddg|y)\Z SinkAdapter
• Error handlers:
    ⇜ StorageError handle