falcon
The no-magic web API and microservices framework for Python developers, with an emphasis on reliability and performance at scale.
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FastAPI framework, high performance, easy to learn, fast to code, ready for production
The Python micro framework for building web applications.
The Web framework for perfectionists with deadlines.
The little ASGI framework that shines. 🌟
Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed.
Asynchronous HTTP client/server framework for asyncio and Python
Quick Overview
Falcon is a high-performance Python web framework designed for building fast and scalable web APIs. It encourages the REST architectural style and aims to be both robust and minimalist, allowing developers to build clean and efficient web services.
Pros
- Extremely fast performance, often outperforming other popular Python web frameworks
- Lightweight and minimalist design, with few dependencies
- Highly customizable and extensible
- Strong focus on RESTful API development
Cons
- Steeper learning curve compared to some other Python web frameworks
- Smaller community and ecosystem compared to more established frameworks like Flask or Django
- Limited built-in features, requiring more manual implementation for complex applications
- Not ideal for full-stack web development or projects requiring a lot of built-in functionality
Code Examples
- Basic Falcon application:
import falcon
class HelloResource:
def on_get(self, req, resp):
resp.media = {"message": "Hello, World!"}
app = falcon.App()
app.add_route("/hello", HelloResource())
- Handling parameters in a route:
class ItemResource:
def on_get(self, req, resp, item_id):
resp.media = {"item_id": item_id}
app.add_route("/items/{item_id}", ItemResource())
- Using middleware:
class AuthMiddleware:
def process_request(self, req, resp):
token = req.get_header("Authorization")
if token is None:
raise falcon.HTTPUnauthorized("Auth token required")
app = falcon.App(middleware=[AuthMiddleware()])
Getting Started
To get started with Falcon, follow these steps:
-
Install Falcon:
pip install falcon
-
Create a new Python file (e.g.,
app.py
) and add the following code:import falcon class HelloResource: def on_get(self, req, resp): resp.media = {"message": "Hello, Falcon!"} app = falcon.App() app.add_route("/", HelloResource())
-
Run the application using a WSGI server like Gunicorn:
pip install gunicorn gunicorn app:app
-
Visit
http://localhost:8000
in your browser or use a tool like cURL to test the API.
Competitor Comparisons
FastAPI framework, high performance, easy to learn, fast to code, ready for production
Pros of FastAPI
- Built-in support for asynchronous programming
- Automatic API documentation with Swagger UI and ReDoc
- Type hints and data validation using Pydantic models
Cons of FastAPI
- Steeper learning curve for developers new to type annotations
- Potentially slower for simple applications due to additional overhead
- Requires Python 3.6+ (Falcon supports Python 3.5+)
Code Comparison
FastAPI example:
from fastapi import FastAPI
app = FastAPI()
@app.get("/")
async def root():
return {"message": "Hello World"}
Falcon example:
import falcon
class HelloResource:
def on_get(self, req, resp):
resp.media = {"message": "Hello World"}
app = falcon.App()
app.add_route("/", HelloResource())
Both frameworks offer lightweight and fast performance for building APIs. FastAPI provides more built-in features and automatic documentation, while Falcon focuses on simplicity and flexibility. The choice between them depends on project requirements and developer preferences.
The Python micro framework for building web applications.
Pros of Flask
- Larger community and ecosystem, with more extensions and third-party libraries
- Simpler and more intuitive API, making it easier for beginners to get started
- Better documentation and more comprehensive tutorials available
Cons of Flask
- Generally slower performance compared to Falcon, especially for high-concurrency applications
- More opinionated and less flexible in certain areas, such as request/response handling
- Heavier footprint, with more dependencies and a larger codebase
Code Comparison
Flask:
from flask import Flask, request
app = Flask(__name__)
@app.route('/hello', methods=['GET'])
def hello():
name = request.args.get('name', 'World')
return f'Hello, {name}!'
Falcon:
import falcon
class HelloResource:
def on_get(self, req, resp):
name = req.get_param('name', default='World')
resp.media = f'Hello, {name}!'
app = falcon.App()
app.add_route('/hello', HelloResource())
Both frameworks offer simple ways to create routes and handle requests, but Falcon's approach is more class-based and explicit, while Flask uses decorators and provides a more concise syntax.
The Web framework for perfectionists with deadlines.
Pros of Django
- Full-featured web framework with built-in admin interface, ORM, and authentication system
- Large ecosystem with extensive third-party packages and community support
- Batteries-included approach, providing a complete solution for web development
Cons of Django
- Can be considered heavyweight for small projects or microservices
- Steeper learning curve due to its comprehensive nature
- Less flexibility in choosing components, as many are tightly integrated
Code Comparison
Django:
from django.urls import path
from . import views
urlpatterns = [
path('', views.index, name='index'),
path('detail/<int:id>/', views.detail, name='detail'),
]
Falcon:
import falcon
class Resource:
def on_get(self, req, resp):
resp.media = {'message': 'Hello, World!'}
app = falcon.App()
app.add_route('/', Resource())
The Django code snippet demonstrates URL routing, while the Falcon example shows a simple API endpoint. Django's routing is more declarative, whereas Falcon's approach is more programmatic and lightweight.
The little ASGI framework that shines. 🌟
Pros of Starlette
- Built-in WebSocket support
- Integrated background tasks and middleware
- Seamless integration with ASGI servers like Uvicorn
Cons of Starlette
- Steeper learning curve for beginners
- Less extensive documentation compared to Falcon
- Smaller community and ecosystem
Code Comparison
Starlette:
from starlette.applications import Starlette
from starlette.responses import JSONResponse
from starlette.routing import Route
async def homepage(request):
return JSONResponse({"message": "Hello, World!"})
app = Starlette(routes=[Route("/", homepage)])
Falcon:
import falcon
class HelloResource:
def on_get(self, req, resp):
resp.media = {"message": "Hello, World!"}
app = falcon.App()
app.add_route("/", HelloResource())
Both frameworks offer lightweight and fast ASGI-compatible solutions for building web applications and APIs. Starlette provides more built-in features and async support out of the box, while Falcon focuses on simplicity and performance. The choice between them depends on specific project requirements and developer preferences.
Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed.
Pros of Tornado
- More mature and battle-tested, with a larger community and ecosystem
- Built-in support for WebSockets and long-polling
- Includes a template engine and form handling utilities
Cons of Tornado
- Heavier and more complex, with a steeper learning curve
- Less modular design, making it harder to use only specific components
- Slower performance compared to more modern ASGI frameworks
Code Comparison
Tornado:
class MainHandler(tornado.web.RequestHandler):
def get(self):
self.write("Hello, World!")
app = tornado.web.Application([
(r"/", MainHandler),
])
Falcon:
class MainResource:
def on_get(self, req, resp):
resp.text = "Hello, World!"
app = falcon.App()
app.add_route("/", MainResource())
Summary
Tornado is a more comprehensive web framework with built-in features for WebSockets and templating, making it suitable for complex applications. However, it's heavier and slower than Falcon. Falcon, on the other hand, is lightweight, fast, and focuses on building clean REST APIs. It's more modular but lacks some of Tornado's built-in features. The choice between them depends on the specific requirements of your project and your preference for simplicity versus feature completeness.
Asynchronous HTTP client/server framework for asyncio and Python
Pros of aiohttp
- Built on asyncio, providing native support for asynchronous programming
- Comprehensive library with both client and server capabilities
- Extensive documentation and large community support
Cons of aiohttp
- Steeper learning curve, especially for developers new to async programming
- More complex setup and configuration compared to Falcon's simplicity
- Potentially higher memory usage due to its broader feature set
Code Comparison
aiohttp server example:
from aiohttp import web
async def hello(request):
return web.Response(text="Hello, World!")
app = web.Application()
app.add_routes([web.get('/', hello)])
web.run_app(app)
Falcon server example:
import falcon
class HelloResource:
def on_get(self, req, resp):
resp.text = "Hello, World!"
app = falcon.App()
app.add_route('/', HelloResource())
Summary
aiohttp is a versatile async library with both client and server capabilities, built on asyncio. It offers more features but comes with increased complexity. Falcon, on the other hand, focuses on simplicity and performance for building APIs. The choice between them depends on project requirements, with aiohttp being more suitable for complex async applications and Falcon for straightforward, high-performance APIs.
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.. image:: https://raw.githubusercontent.com/falconry/falcon/master/logo/banner.jpg :align: center :alt: Falcon logo :target: https://falconframework.org/ :width: 100 %
|Build status| |Docs| |codecov.io| |PyPI package| |Python versions|
The Falcon Web Framework
Falcon <https://falconframework.org>
__ is a minimalist ASGI/WSGI framework for
building mission-critical REST APIs and microservices, with a focus on
reliability, correctness, and performance at scale.
When it comes to building HTTP APIs, other frameworks weigh you down with tons of dependencies and unnecessary abstractions. Falcon cuts to the chase with a clean design that embraces HTTP and the REST architectural style.
Falcon apps work with any WSGI <https://www.python.org/dev/peps/pep-3333/>
_
or ASGI <https://asgi.readthedocs.io/en/latest/>
_ server, and run like a
champ under CPython 3.8+ and PyPy 3.8+.
Quick Links
Read the docs <https://falcon.readthedocs.io/en/stable>
_ (FAQ <https://falcon.readthedocs.io/en/stable/user/faq.html>
_ -getting help <https://falcon.readthedocs.io/en/stable/community/help.html>
_ -reference <https://falcon.readthedocs.io/en/stable/api/index.html>
_)Falcon add-ons and complementary packages <https://github.com/falconry/falcon/wiki>
_Falcon articles, talks and podcasts <https://github.com/falconry/falcon/wiki/Articles,-Talks-and-Podcasts>
_falconry/user for Falcon users <https://gitter.im/falconry/user>
_ @ Gitterfalconry/dev for Falcon contributors <https://gitter.im/falconry/dev>
_ @ Gitter
What People are Saying
"Falcon is rock solid and it's fast."
"We have been using Falcon as a replacement for [another framework] and we simply love the performance (three times faster) and code base size (easily half of our [original] code)."
"I'm loving #falconframework! Super clean and simple, I finally have the speed and flexibility I need!"
"Falcon looks great so far. I hacked together a quick test for a tiny server of mine and was ~40% faster with only 20 minutes of work."
"I feel like I'm just talking HTTP at last, with nothing in the middle. Falcon seems like the requests of backend."
"The source code for Falcon is so good, I almost prefer it to documentation. It basically can't be wrong."
"What other framework has integrated support for 786 TRY IT NOW ?"
Features
Falcon tries to do as little as possible while remaining highly effective.
- ASGI, WSGI, and WebSocket support
- Native
asyncio
support - No reliance on magic globals for routing and state management
- Stable interfaces with an emphasis on backwards-compatibility
- Simple API modeling through centralized RESTful routing
- Highly-optimized, extensible code base
- Easy access to headers and bodies through request and response classes
- DRY request processing via middleware components and hooks
- Strict adherence to RFCs
- Idiomatic HTTP error responses
- Straightforward exception handling
- Snappy testing with WSGI/ASGI helpers and mocks
- CPython 3.8+ and PyPy 3.8+ support
.. Patron list starts here. For Python package, we substitute this section with: Support Falcon Development
A Big Thank You to Our Patrons!
|Backer:GovCert| |Backer:Sentry|
Has Falcon helped you make an awesome app? Show your support today with a one-time donation or by becoming a patron. Supporters get cool gear, an opportunity to promote their brand to Python developers, and prioritized support.
Learn how to support Falcon development <https://falconframework.org/#sectionSupportFalconDevelopment>
_
Thanks!
How is Falcon Different?
Perfection is finally attained not when there is no longer anything
to add, but when there is no longer anything to take away.
*- Antoine de Saint-Exupéry*
We designed Falcon to support the demanding needs of large-scale microservices and responsive app backends. Falcon complements more general Python web frameworks by providing bare-metal performance, reliability, and flexibility wherever you need it.
Reliable. We go to great lengths to avoid introducing breaking changes, and
when we do they are fully documented and only introduced (in the spirit of
SemVer <http://semver.org/>
_) with a major version increment. The code is
rigorously tested with numerous inputs and we require 100% coverage at all
times. Falcon has no dependencies outside the standard library, helping
minimize your app's attack surface while avoiding transitive bugs and breaking
changes.
Debuggable. Falcon eschews magic. It's easy to tell which inputs lead to which outputs. Unhandled exceptions are never encapsulated or masked. Potentially surprising behaviors, such as automatic request body parsing, are well-documented and disabled by default. Finally, when it comes to the framework itself, we take care to keep logic paths simple and understandable. All this makes it easier to reason about the code and to debug edge cases in large-scale deployments.
Fast. Same hardware, more requests. Falcon turns around requests
significantly faster than other popular Python frameworks like Django and
Flask. For an extra speed boost, Falcon compiles itself with Cython when
available, and also works well with PyPy <https://pypy.org>
_. Considering a
move to another programming language? Benchmark with Falcon+PyPy first!
Flexible. Falcon leaves a lot of decisions and implementation details to
you, the API developer. This gives you a lot of freedom to customize and tune
your implementation. It also helps you understand your apps at a deeper level,
making them easier to tune, debug, and refactor over the long run. Falcon's
minimalist design provides space for Python community members to independently
innovate on Falcon add-ons and complementary packages <https://github.com/falconry/falcon/wiki>
_.
Who's Using Falcon?
Falcon is used around the world by a growing number of organizations, including:
- 7ideas
- Cronitor
- EMC
- Hurricane Electric
- Leadpages
- OpenStack
- Rackspace
- Shiftgig
- tempfil.es
- Opera Software
If you are using the Falcon framework for a community or commercial
project, please consider adding your information to our wiki under
Who's Using Falcon? <https://github.com/falconry/falcon/wiki/Who's-using-Falcon%3F>
_
Community
A number of Falcon add-ons, templates, and complementary packages are
available for use in your projects. We've listed several of these on the
Falcon wiki <https://github.com/falconry/falcon/wiki>
_ as a starting
point, but you may also wish to search PyPI for additional resources.
The Falconry community on Gitter is a great place to ask questions and
share your ideas. You can find us in falconry/user <https://gitter.im/falconry/user>
. We also have a
falconry/dev <https://gitter.im/falconry/dev>
room for discussing
the design and development of the framework itself.
Per our
Code of Conduct <https://github.com/falconry/falcon/blob/master/CODEOFCONDUCT.md>
_,
we expect everyone who participates in community discussions to act
professionally, and lead by example in encouraging constructive
discussions. Each individual in the community is responsible for
creating a positive, constructive, and productive culture.
Installation
PyPy ^^^^
PyPy <http://pypy.org/>
__ is the fastest way to run your Falcon app.
PyPy3.8+ is supported as of PyPy v7.3.7+.
.. code:: bash
$ pip install falcon
Or, to install the latest beta or release candidate, if any:
.. code:: bash
$ pip install --pre falcon
CPython ^^^^^^^
Falcon also fully supports
CPython <https://www.python.org/downloads/>
__ 3.8+.
The latest stable version of Falcon can be installed directly from PyPI:
.. code:: bash
$ pip install falcon
Or, to install the latest beta or release candidate, if any:
.. code:: bash
$ pip install --pre falcon
In order to provide an extra speed boost, Falcon automatically compiles itself
with Cython <https://cython.org/>
__ under any
PEP 517 <https://peps.python.org/pep-0517/>
__-compliant installer.
For your convenience, wheels containing pre-compiled binaries are available
from PyPI for the majority of common platforms. Even if a binary build for your
platform of choice is not available, pip
will pick a pure-Python wheel.
You can also cythonize Falcon for your environment; see our
Installation docs <https://falcon.readthedocs.io/en/stable/user/install.html>
__
for more information on this and other advanced options.
Dependencies ^^^^^^^^^^^^
Falcon does not require the installation of any other packages.
WSGI Server
Falcon speaks WSGI <https://www.python.org/dev/peps/pep-3333/>
_ (or
ASGI <https://asgi.readthedocs.io/en/latest/>
_; see also below). In order to
serve a Falcon app, you will need a WSGI server. Gunicorn and uWSGI are some of
the more popular ones out there, but anything that can load a WSGI app will do.
.. code:: bash
$ pip install [gunicorn|uwsgi]
ASGI Server
In order to serve a Falcon ASGI app, you will need an ASGI server. Uvicorn is a popular choice:
.. code:: bash
$ pip install uvicorn
Source Code
Falcon lives on GitHub <https://github.com/falconry/falcon>
_, making the
code easy to browse, download, fork, etc. Pull requests are always welcome! Also,
please remember to star the project if it makes you happy. :)
Once you have cloned the repo or downloaded a tarball from GitHub, you can install Falcon like this:
.. code:: bash
$ cd falcon
$ pip install .
Or, if you want to edit the code, first fork the main repo, clone the fork to your desktop, and then run the following to install it using symbolic linking, so that when you change your code, the changes will be automagically available to your app without having to reinstall the package:
.. code:: bash
$ cd falcon
$ FALCON_DISABLE_CYTHON=Y pip install -e .
You can manually test changes to the Falcon framework by switching to the directory of the cloned repo and then running pytest:
.. code:: bash
$ cd falcon
$ pip install -r requirements/tests
$ pytest tests
Or, to run the default set of tests:
.. code:: bash
$ pip install tox && tox
See also the tox.ini <https://github.com/falconry/falcon/blob/master/tox.ini>
_
file for a full list of available environments.
Read the Docs
The docstrings in the Falcon code base are quite extensive, and we recommend keeping a REPL running while learning the framework so that you can query the various modules and classes as you have questions.
Online docs are available at: https://falcon.readthedocs.io
You can build the same docs locally as follows:
.. code:: bash
$ pip install tox && tox -e docs
Once the docs have been built, you can view them by opening the following index page in your browser. On OS X it's as simple as::
$ open docs/_build/html/index.html
Or on Linux:
.. code:: bash
$ xdg-open docs/_build/html/index.html
Getting Started
Here is a simple, contrived example showing how to create a Falcon-based WSGI app (the ASGI version is included further down):
.. code:: python
# 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'
'\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
httpd.serve_forever()
You can run the above example directly using the included wsgiref server:
.. code:: bash
$ pip install falcon
$ python things.py
Then, in another terminal:
.. code:: bash
$ curl localhost:8000/things
The ASGI version of the example is similar:
.. code:: python
# examples/things_asgi.py
import falcon
import falcon.asgi
# 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:
async 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'
'\n'
' ~ Immanuel Kant\n\n')
# falcon.asgi.App instances are callable ASGI apps...
# in larger applications the app is created in a separate file
app = falcon.asgi.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)
You can run the ASGI version with uvicorn or any other ASGI server:
.. code:: bash
$ pip install falcon uvicorn
$ uvicorn things_asgi:app
A More Complex Example (WSGI)
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 <https://pypi.org/project/requests/>
_ package has been installed.
(For the equivalent ASGI app, see: A More Complex Example (ASGI)
_).
.. code:: python
# 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):
@staticmethod
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 = str(result.status_code) + ' ' + result.reason
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',
description=description,
challenges=challenges,
href='http://docs.example.com/auth')
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',
description=description,
challenges=challenges,
href='http://docs.example.com/auth')
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.',
href='http://docs.examples.com/api/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.',
href='http://docs.examples.com/api/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
return
body = req.stream.read()
if not body:
raise falcon.HTTPBadRequest(title='Empty request body',
description='A valid JSON document is required.')
try:
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 '
'UTF-8.')
raise falcon.HTTPBadRequest(title='Malformed JSON',
description=description)
def process_response(self, req, resp, resource, req_succeeded):
if not hasattr(resp.context, 'result'):
return
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.HTTPContentTooLarge(
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
try:
result = self.db.get_things(marker, limit)
except Exception as ex:
self.logger.error(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):
try:
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(middleware=[
AuthMiddleware(),
RequireJSON(),
JSONTranslator(),
])
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('127.0.0.1', 8000, app)
httpd.serve_forever()
Again this code uses wsgiref, but you can also run the above example using any WSGI server, such as uWSGI or Gunicorn. For example:
.. code:: bash
$ pip install requests gunicorn
$ gunicorn things:app
On Windows you can run Gunicorn and uWSGI via WSL, or you might try Waitress:
.. code:: bash
$ pip install requests waitress
$ waitress-serve --port=8000 things:app
To test this example, open another terminal and run:
.. code:: bash
$ http localhost:8000/1/things authorization:custom-token
You can also view the application configuration from the CLI via the
falcon-inspect-app
script that is bundled with the framework:
.. code:: bash
falcon-inspect-app things_advanced:app
A More Complex Example (ASGI)
Here's the ASGI version of the app from above. Note that it uses the
httpx <https://pypi.org/project/httpx/>
_ package in lieu of
requests <https://pypi.org/project/requests/>
_.
.. code:: python
# examples/things_advanced_asgi.py
import json
import logging
import uuid
import falcon
import falcon.asgi
import httpx
class StorageEngine:
async def get_things(self, marker, limit):
return [{'id': str(uuid.uuid4()), 'color': 'green'}]
async def add_thing(self, thing):
thing['id'] = str(uuid.uuid4())
return thing
class StorageError(Exception):
@staticmethod
async 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',
}
async def __call__(self, req, resp, engine):
url = self.engines[engine]
params = {'q': req.get_param('q', True)}
async with httpx.AsyncClient() as client:
result = await client.get(url, params=params)
resp.status = result.status_code
resp.content_type = result.headers['content-type']
resp.text = result.text
class AuthMiddleware:
async 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',
description=description,
challenges=challenges,
href='http://docs.example.com/auth')
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',
description=description,
challenges=challenges,
href='http://docs.example.com/auth')
def _token_is_valid(self, token, account_id):
return True # Suuuuuure it's valid...
class RequireJSON:
async def process_request(self, req, resp):
if not req.client_accepts_json:
raise falcon.HTTPNotAcceptable(
description='This API only supports responses encoded as JSON.',
href='http://docs.examples.com/api/json')
if req.method in ('POST', 'PUT'):
if 'application/json' not in req.content_type:
raise falcon.HTTPUnsupportedMediaType(
description='This API only supports requests encoded as JSON.',
href='http://docs.examples.com/api/json')
class JSONTranslator:
# NOTE: Normally you would simply use req.get_media() and resp.media for
# this particular use case; this example serves only to illustrate
# what is possible.
async def process_request(self, req, resp):
# NOTE: Test explicitly for 0, since this property could be None in
# the case that the Content-Length header is missing (in which case we
# can't know if there is a body without actually attempting to read
# it from the request stream.)
if req.content_length == 0:
# Nothing to do
return
body = await req.stream.read()
if not body:
raise falcon.HTTPBadRequest(title='Empty request body',
description='A valid JSON document is required.')
try:
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 '
'UTF-8.')
raise falcon.HTTPBadRequest(title='Malformed JSON',
description=description)
async def process_response(self, req, resp, resource, req_succeeded):
if not hasattr(resp.context, 'result'):
return
resp.text = json.dumps(resp.context.result)
def max_body(limit):
async 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.HTTPContentTooLarge(
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__)
async def on_get(self, req, resp, user_id):
marker = req.get_param('marker') or ''
limit = req.get_param_as_int('limit') or 50
try:
result = await self.db.get_things(marker, limit)
except Exception as ex:
self.logger.error(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))
async def on_post(self, req, resp, user_id):
try:
doc = req.context.doc
except AttributeError:
raise falcon.HTTPBadRequest(
title='Missing thing',
description='A thing must be submitted in the request body.')
proper_thing = await self.db.add_thing(doc)
resp.status = falcon.HTTP_201
resp.location = '/%s/things/%s' % (user_id, proper_thing['id'])
# The app instance is an ASGI callable
app = falcon.asgi.App(middleware=[
# AuthMiddleware(),
RequireJSON(),
JSONTranslator(),
])
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')
You can run the ASGI version with any ASGI server, such as uvicorn:
.. code:: bash
$ pip install falcon httpx uvicorn
$ uvicorn things_advanced_asgi:app
Contributing
Thanks for your interest in the project! We welcome pull requests from developers of all skill levels. To get started, simply fork the master branch on GitHub to your personal account and then clone the fork into your development environment.
If you would like to contribute but don't already have something in mind,
we invite you to take a look at the issues listed under our
next milestone <https://github.com/falconry/falcon/milestones>
_.
If you see one you'd like to work on, please leave a quick comment so that we don't
end up with duplicated effort. Thanks in advance!
Please note that all contributors and maintainers of this project are subject to our
Code of Conduct <https://github.com/falconry/falcon/blob/master/CODEOFCONDUCT.md>
_.
Before submitting a pull request, please ensure you have added/updated the appropriate tests (and that all existing tests still pass with your changes), and that your coding style follows PEP 8 and doesn't cause pyflakes to complain.
Commit messages should be formatted using AngularJS conventions <https://github.com/angular/angular.js/blob/master/DEVELOPERS.md#-git-commit-guidelines>
__.
Comments follow Google's style guide <https://google.github.io/styleguide/pyguide.html?showone=Comments#Comments>
__,
with the additional requirement of prefixing inline comments using your
GitHub nick and an appropriate prefix:
- TODO(riker): Damage report!
- NOTE(riker): Well, that's certainly good to know.
- PERF(riker): Travel time to the nearest starbase?
- APPSEC(riker): In all trust, there is the possibility for betrayal.
The core Falcon project maintainers are:
- Kurt Griffiths, Project Lead (kgriffs on GH, Gitter, and Twitter)
- John Vrbanac (jmvrbanac on GH, Gitter, and Twitter)
- Vytautas Liuolia (vytas7 on GH and Gitter, and vliuolia on Twitter)
- Nick Zaccardi (nZac on GH and Gitter)
- Federico Caselli (CaselIT on GH and Gitter)
Please don't hesitate to reach out if you have any questions, or just need a
little help getting started. You can find us in
falconry/dev <https://gitter.im/falconry/dev>
_ on Gitter.
See also: CONTRIBUTING.md <https://github.com/falconry/falcon/blob/master/CONTRIBUTING.md>
__
Legal
Copyright 2013-2025 by Individual and corporate contributors as noted in the individual source files.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use any portion of the Falcon framework except in compliance with the License. Contributors agree to license their work under the same License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
.. |Build status| image:: https://github.com/falconry/falcon/actions/workflows/tests.yaml/badge.svg :target: https://github.com/falconry/falcon/actions/workflows/tests.yaml .. |Docs| image:: https://readthedocs.org/projects/falcon/badge/?version=stable :alt: Falcon web framework docs :target: https://falcon.readthedocs.io/en/stable/?badge=stable .. |codecov.io| image:: https://codecov.io/gh/falconry/falcon/branch/master/graphs/badge.svg :target: https://codecov.io/gh/falconry/falcon .. |PyPI package| image:: https://badge.fury.io/py/falcon.svg :target: https://pypi.org/project/falcon/ .. |Python versions| image:: https://img.shields.io/pypi/pyversions/falcon.svg :target: https://pypi.org/project/falcon/ .. |Backer:GovCert| image:: https://falconframework.org/assets/govcert.png :alt: CERT Gouvernemental Luxembourg :height: 60px :target: https://www.govcert.lu/ .. |Backer:Sentry| image:: https://falconframework.org/assets/sentry-dark.svg :alt: Sentry :height: 60px :target: https://sentry.io
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