The App Class¶
Falcon supports both the WSGI (falcon.App
) and
ASGI (falcon.asgi.App
) protocols. This is done
by instantiating the respective App
class to create a
callable WSGI or ASGI “application”.
Because Falcon’s App
classes are built on
WSGI and
ASGI,
you can host them with any standard-compliant server.
import falcon
import falcon.asgi
wsgi_app = falcon.App()
asgi_app = falcon.asgi.App()
WSGI App¶
- class falcon.App(media_type='application/json', request_type=<class 'falcon.request.Request'>, response_type=<class 'falcon.response.Response'>, middleware=None, router=None, independent_middleware=True, cors_enable=False, sink_before_static_route=True)[source]¶
This class is the main entry point into a Falcon-based WSGI app.
Each App instance provides a callable WSGI interface and a routing engine (for ASGI applications, see
falcon.asgi.App
).Note
The
API
class was renamed toApp
in Falcon 3.0. The old class name remains available as an alias for backwards-compatibility, but will be removed in a future release.- Keyword Arguments:
media_type (str) – Default media type to use when initializing
RequestOptions
andResponseOptions
. Thefalcon
module provides a number of constants for common media types, such asfalcon.MEDIA_MSGPACK
,falcon.MEDIA_YAML
,falcon.MEDIA_XML
, etc.middleware –
Either a single middleware component object or an iterable of objects (instantiated classes) that implement the following middleware component interface. Note that it is only necessary to implement the methods for the events you would like to handle; Falcon simply skips over any missing middleware methods:
class ExampleComponent: def process_request(self, req, resp): """Process the request before routing it. Note: Because Falcon routes each request based on req.path, a request can be effectively re-routed by setting that attribute to a new value from within process_request(). Args: req: Request object that will eventually be routed to an on_* responder method. resp: Response object that will be routed to the on_* responder. """ def process_resource(self, req, resp, resource, params): """Process the request and resource *after* routing. Note: This method is only called when the request matches a route to a resource. Args: req: Request object that will be passed to the routed responder. resp: Response object that will be passed to the responder. resource: Resource object to which the request was routed. May be None if no route was found for the request. params: A dict-like object representing any additional params derived from the route's URI template fields, that will be passed to the resource's responder method as keyword arguments. """ def process_response(self, req, resp, resource, req_succeeded) """Post-processing of the response (after routing). Args: req: Request object. resp: Response object. resource: Resource object to which the request was routed. May be None if no route was found for the request. req_succeeded: True if no exceptions were raised while the framework processed and routed the request; otherwise False. """
(See also: Middleware)
request_type –
Request
-like class to use instead of Falcon’s default class. Among other things, this feature affords inheriting fromfalcon.Request
in order to override thecontext_type
class variable (default:falcon.Request
)response_type –
Response
-like class to use instead of Falcon’s default class (default:falcon.Response
)router (object) – An instance of a custom router to use in lieu of the default engine. (See also: Custom Routers)
independent_middleware (bool) – Set to
False
if response middleware should not be executed independently of whether or not request middleware raises an exception (defaultTrue
). When this option is set toFalse
, a middleware component’sprocess_response()
method will NOT be called when that same component’sprocess_request()
(or that of a component higher up in the stack) raises an exception.cors_enable (bool) – Set this flag to
True
to enable a simple CORS policy for all responses, including support for preflighted requests. An instance ofCORSMiddleware
can instead be passed to the middleware argument to customize its behaviour. (defaultFalse
). (See also: CORS)sink_before_static_route (bool) – Indicates if the sinks should be processed before (when
True
) or after (whenFalse
) the static routes. This has an effect only if no route was matched. (defaultTrue
)
- req_options¶
A set of behavioral options related to incoming requests. (See also:
RequestOptions
)
- resp_options¶
A set of behavioral options related to outgoing responses. (See also:
ResponseOptions
)
- router_options¶
Configuration options for the router. If a custom router is in use, and it does not expose any configurable options, referencing this attribute will raise an instance of
AttributeError
.(See also: CompiledRouterOptions)
- add_error_handler(exception, handler=None)[source]¶
Register a handler for one or more exception types.
Error handlers may be registered for any exception type, including
HTTPError
orHTTPStatus
. This feature provides a central location for logging and otherwise handling exceptions raised by responders, hooks, and middleware components.A handler can raise an instance of
HTTPError
orHTTPStatus
to communicate information about the issue to the client. Alternatively, a handler may modify resp directly.An error handler “matches” a raised exception if the exception is an instance of the corresponding exception type. If more than one error handler matches the raised exception, the framework will choose the most specific one, as determined by the method resolution order of the raised exception type. If multiple error handlers are registered for the same exception class, then the most recently-registered handler is used.
For example, suppose we register error handlers as follows:
app = App() app.add_error_handler(falcon.HTTPNotFound, custom_handle_not_found) app.add_error_handler(falcon.HTTPError, custom_handle_http_error) app.add_error_handler(Exception, custom_handle_uncaught_exception) app.add_error_handler(falcon.HTTPNotFound, custom_handle_404)
If an instance of
falcon.HTTPForbidden
is raised, it will be handled bycustom_handle_http_error()
.falcon.HTTPError
is a superclass offalcon.HTTPForbidden
and a subclass ofException
, so it is the most specific exception type with a registered handler.If an instance of
falcon.HTTPNotFound
is raised, it will be handled bycustom_handle_404()
, not bycustom_handle_not_found()
, becausecustom_handle_404()
was registered more recently.Note
By default, the framework installs three handlers, one for
HTTPError
, one forHTTPStatus
, and one for the standardException
type, which prevents passing uncaught exceptions to the WSGI server. These can be overridden by adding a custom error handler method for the exception type in question.- Parameters:
exception (type or iterable of types) – When handling a request, whenever an error occurs that is an instance of the specified type(s), the associated handler will be called. Either a single type or an iterable of types may be specified.
handler (callable) –
A function or callable object taking the form
func(req, resp, ex, params)
.If not specified explicitly, the handler will default to
exception.handle
, whereexception
is the error type specified above, andhandle
is a static method (i.e., decorated with@staticmethod
) that accepts the same params just described. For example:class CustomException(CustomBaseException): @staticmethod def handle(req, resp, ex, params): # TODO: Log the error # Convert to an instance of falcon.HTTPError raise falcon.HTTPError(falcon.HTTP_792)
If an iterable of exception types is specified instead of a single type, the handler must be explicitly specified.
Changed in version 3.0: The error handler is now selected by the most-specific matching error class, rather than the most-recently registered matching error class.
- add_middleware(middleware)[source]¶
Add one or more additional middleware components.
- Parameters:
middleware – Either a single middleware component or an iterable of components to add. The component(s) will be invoked, in order, as if they had been appended to the original middleware list passed to the class initializer.
- add_route(uri_template, resource, **kwargs)[source]¶
Associate a templatized URI path with a resource.
Falcon routes incoming requests to resources based on a set of URI templates. If the path requested by the client matches the template for a given route, the request is then passed on to the associated resource for processing.
Note
If no route matches the request, control then passes to a default responder that simply raises an instance of
HTTPRouteNotFound
. By default, this error will be rendered as a 404 response, but this behavior can be modified by adding a custom error handler (see also this FAQ topic).On the other hand, if a route is matched but the resource does not implement a responder for the requested HTTP method, the framework invokes a default responder that raises an instance of
HTTPMethodNotAllowed
.This method delegates to the configured router’s
add_route()
method. To override the default behavior, pass a custom router object to theApp
initializer.(See also: Routing)
- Parameters:
uri_template (str) –
A templatized URI. Care must be taken to ensure the template does not mask any sink patterns, if any are registered.
(See also:
add_sink()
)Warning
If
strip_url_path_trailing_slash
is enabled, uri_template should be provided without a trailing slash.(See also: How does Falcon handle a trailing slash in the request path?)
resource (instance) –
Object which represents a REST resource. Falcon will pass GET requests to
on_get()
, PUT requests toon_put()
, etc. If any HTTP methods are not supported by your resource, simply don’t define the corresponding request handlers, and Falcon will do the right thing.Note
When using an async version of the
App
, all request handlers must be awaitable coroutine functions.
- Keyword Arguments:
suffix (str) –
Optional responder name suffix for this route. If a suffix is provided, Falcon will map GET requests to
on_get_{suffix}()
, POST requests toon_post_{suffix}()
, etc. In this way, multiple closely-related routes can be mapped to the same resource. For example, a single resource class can use suffixed responders to distinguish requests for a single item vs. a collection of those same items. Another class might use a suffixed responder to handle a shortlink route in addition to the regular route for the resource. For example:class Baz(object): def on_get_foo(self, req, resp): pass def on_get_bar(self, req, resp): pass baz = Baz() app = falcon.App() app.add_route('/foo', baz, suffix='foo') app.add_route('/bar', baz, suffix='bar')
compile (bool) – Optional flag that can be provided when using the default
CompiledRouter
to compile the routing logic on this call, since it will otherwise delay compilation until the first request is routed. SeeCompiledRouter.add_route()
for further details.
Note
Any additional keyword arguments not defined above are passed through to the underlying router’s
add_route()
method. The default router ignores any additional keyword arguments, but custom routers may take advantage of this feature to receive additional options when setting up routes. Custom routers MUST accept such arguments using the variadic pattern (**kwargs
), and ignore any keyword arguments that they don’t support.
- add_sink(sink, prefix='/')[source]¶
Register a sink method for the App.
If no route matches a request, but the path in the requested URI matches a sink prefix, Falcon will pass control to the associated sink, regardless of the HTTP method requested.
Using sinks, you can drain and dynamically handle a large number of routes, when creating static resources and responders would be impractical. For example, you might use a sink to create a smart proxy that forwards requests to one or more backend services.
- Parameters:
sink (callable) –
A callable taking the form
func(req, resp, **kwargs)
.Note
When using an async version of the
App
, this must be a coroutine.prefix (str) –
A regex string, typically starting with ‘/’, which will trigger the sink if it matches the path portion of the request’s URI. Both strings and precompiled regex objects may be specified. Characters are matched starting at the beginning of the URI path.
Note
Named groups are converted to kwargs and passed to the sink as such.
Warning
If the prefix overlaps a registered route template, the route will take precedence and mask the sink.
(See also:
add_route()
)
- add_static_route(prefix, directory, downloadable=False, fallback_filename=None)[source]¶
Add a route to a directory of static files.
Static routes provide a way to serve files directly. This feature provides an alternative to serving files at the web server level when you don’t have that option, when authorization is required, or for testing purposes.
Warning
Serving files directly from the web server, rather than through the Python app, will always be more efficient, and therefore should be preferred in production deployments. For security reasons, the directory and the fallback_filename (if provided) should be read only for the account running the application.
Warning
If you need to serve large files and/or progressive downloads (such as in the case of video streaming) through the Falcon app, check that your application server’s timeout settings can accomodate the expected request duration (for instance, the popular Gunicorn kills
sync
workers after 30 seconds unless configured otherwise).Note
For ASGI apps, file reads are made non-blocking by scheduling them on the default executor.
Static routes are matched in LIFO order. Therefore, if the same prefix is used for two routes, the second one will override the first. This also means that more specific routes should be added after less specific ones. For example, the following sequence would result in
'/foo/bar/thing.js'
being mapped to the'/foo/bar'
route, and'/foo/xyz/thing.js'
being mapped to the'/foo'
route:app.add_static_route('/foo', foo_path) app.add_static_route('/foo/bar', foobar_path)
- Parameters:
prefix (str) –
The path prefix to match for this route. If the path in the requested URI starts with this string, the remainder of the path will be appended to the source directory to determine the file to serve. This is done in a secure manner to prevent an attacker from requesting a file outside the specified directory.
Note that static routes are matched in LIFO order, and are only attempted after checking dynamic routes and sinks.
directory (Union[str, pathlib.Path]) – The source directory from which to serve files.
downloadable (bool) – Set to
True
to include a Content-Disposition header in the response. The “filename” directive is simply set to the name of the requested file.fallback_filename (str) – Fallback filename used when the requested file is not found. Can be a relative path inside the prefix folder or any valid absolute path.
- set_error_serializer(serializer)[source]¶
Override the default serializer for instances of
HTTPError
.When a responder raises an instance of
HTTPError
, Falcon converts it to an HTTP response automatically. The default serializer supports JSON and XML, but may be overridden by this method to use a custom serializer in order to support other media types.Note
If a custom media type is used and the type includes a “+json” or “+xml” suffix, the default serializer will convert the error to JSON or XML, respectively.
Note
A custom serializer set with this method may not be called if the default error handler for
HTTPError
has been overriden. Seeadd_error_handler()
for more details.The
HTTPError
class contains helper methods, such as to_json() and to_dict(), that can be used from within custom serializers. For example:def my_serializer(req, resp, exception): representation = None preferred = req.client_prefers((falcon.MEDIA_YAML, falcon.MEDIA_JSON)) if preferred is not None: if preferred == falcon.MEDIA_JSON: resp.data = exception.to_json() else: resp.text = yaml.dump(exception.to_dict(), encoding=None) resp.content_type = preferred resp.append_header('Vary', 'Accept')
- Parameters:
serializer (callable) – A function taking the form
func(req, resp, exception)
, where req is the request object that was passed to the responder method, resp is the response object, and exception is an instance offalcon.HTTPError
.
ASGI App¶
- class falcon.asgi.App(*args, request_type=<class 'falcon.asgi.request.Request'>, response_type=<class 'falcon.asgi.response.Response'>, **kwargs)[source]¶
This class is the main entry point into a Falcon-based ASGI app.
Each App instance provides a callable ASGI interface and a routing engine (for WSGI applications, see
falcon.App
).- Keyword Arguments:
media_type (str) – Default media type to use when initializing
RequestOptions
andResponseOptions
. Thefalcon
module provides a number of constants for common media types, such asfalcon.MEDIA_MSGPACK
,falcon.MEDIA_YAML
,falcon.MEDIA_XML
, etc.middleware –
Either a single middleware component object or an iterable of objects (instantiated classes) that implement the middleware component interface shown below.
The interface provides support for handling both ASGI worker lifespan events and per-request events. However, because lifespan events are an optional part of the ASGI specification, they may or may not fire depending on your ASGI server.
A lifespan event handler can be used to perform startup or shutdown activities for the main event loop. An example of this would be creating a connection pool and subsequently closing the connection pool to release the connections.
Note
In a multi-process environment, lifespan events will be triggered independently for the individual event loop associated with each process.
Note
The framework requires that all middleware methods be implemented as coroutine functions via async def. However, it is possible to implement middleware classes that support both ASGI and WSGI apps by distinguishing the ASGI methods with an *_async postfix (see also: Middleware).
It is only necessary to implement the methods for the events you would like to handle; Falcon simply skips over any missing middleware methods:
class ExampleComponent: async def process_startup(self, scope, event): """Process the ASGI lifespan startup event. Invoked when the server is ready to start up and receive connections, but before it has started to do so. To halt startup processing and signal to the server that it should terminate, simply raise an exception and the framework will convert it to a "lifespan.startup.failed" event for the server. Args: scope (dict): The ASGI scope dictionary for the lifespan protocol. The lifespan scope exists for the duration of the event loop. event (dict): The ASGI event dictionary for the startup event. """ async def process_shutdown(self, scope, event): """Process the ASGI lifespan shutdown event. Invoked when the server has stopped accepting connections and closed all active connections. To halt shutdown processing and signal to the server that it should immediately terminate, simply raise an exception and the framework will convert it to a "lifespan.shutdown.failed" event for the server. Args: scope (dict): The ASGI scope dictionary for the lifespan protocol. The lifespan scope exists for the duration of the event loop. event (dict): The ASGI event dictionary for the shutdown event. """ async def process_request(self, req, resp): """Process the request before routing it. Note: Because Falcon routes each request based on req.path, a request can be effectively re-routed by setting that attribute to a new value from within process_request(). Args: req: Request object that will eventually be routed to an on_* responder method. resp: Response object that will be routed to the on_* responder. """ async def process_resource(self, req, resp, resource, params): """Process the request and resource *after* routing. Note: This method is only called when the request matches a route to a resource. Args: req: Request object that will be passed to the routed responder. resp: Response object that will be passed to the responder. resource: Resource object to which the request was routed. May be ``None`` if no route was found for the request. params: A dict-like object representing any additional params derived from the route's URI template fields, that will be passed to the resource's responder method as keyword arguments. """ async def process_response(self, req, resp, resource, req_succeeded) """Post-processing of the response (after routing). Args: req: Request object. resp: Response object. resource: Resource object to which the request was routed. May be ``None`` if no route was found for the request. req_succeeded: True if no exceptions were raised while the framework processed and routed the request; otherwise False. """
(See also: Middleware)
request_type –
Request
-like class to use instead of Falcon’s default class. Among other things, this feature affords inheriting fromfalcon.asgi.Request
in order to override thecontext_type
class variable (default:falcon.asgi.Request
)response_type –
Response
-like class to use instead of Falcon’s default class (default:falcon.asgi.Response
)router (object) – An instance of a custom router to use in lieu of the default engine. (See also: Custom Routers)
independent_middleware (bool) – Set to
False
if response middleware should not be executed independently of whether or not request middleware raises an exception (defaultTrue
). When this option is set toFalse
, a middleware component’sprocess_response()
method will NOT be called when that same component’sprocess_request()
(or that of a component higher up in the stack) raises an exception.cors_enable (bool) – Set this flag to
True
to enable a simple CORS policy for all responses, including support for preflighted requests. An instance ofCORSMiddleware
can instead be passed to the middleware argument to customize its behaviour. (defaultFalse
). (See also: CORS)sink_before_static_route (bool) – Indicates if the sinks should be processed before (when
True
) or after (whenFalse
) the static routes. This has an effect only if no route was matched. (defaultTrue
)
- req_options¶
A set of behavioral options related to incoming requests. (See also:
RequestOptions
)
- resp_options¶
A set of behavioral options related to outgoing responses. (See also:
ResponseOptions
)
- ws_options¶
A set of behavioral options related to WebSocket connections. (See also:
WebSocketOptions
)
- router_options¶
Configuration options for the router. If a custom router is in use, and it does not expose any configurable options, referencing this attribute will raise an instance of
AttributeError
.(See also: CompiledRouterOptions)
- add_error_handler(exception, handler=None)[source]¶
Register a handler for one or more exception types.
Error handlers may be registered for any exception type, including
HTTPError
orHTTPStatus
. This feature provides a central location for logging and otherwise handling exceptions raised by responders, hooks, and middleware components.A handler can raise an instance of
HTTPError
orHTTPStatus
to communicate information about the issue to the client. Alternatively, a handler may modify resp directly.An error handler “matches” a raised exception if the exception is an instance of the corresponding exception type. If more than one error handler matches the raised exception, the framework will choose the most specific one, as determined by the method resolution order of the raised exception type. If multiple error handlers are registered for the same exception class, then the most recently-registered handler is used.
For example, suppose we register error handlers as follows:
app = App() app.add_error_handler(falcon.HTTPNotFound, custom_handle_not_found) app.add_error_handler(falcon.HTTPError, custom_handle_http_error) app.add_error_handler(Exception, custom_handle_uncaught_exception) app.add_error_handler(falcon.HTTPNotFound, custom_handle_404)
If an instance of
falcon.HTTPForbidden
is raised, it will be handled bycustom_handle_http_error()
.falcon.HTTPError
is a superclass offalcon.HTTPForbidden
and a subclass ofException
, so it is the most specific exception type with a registered handler.If an instance of
falcon.HTTPNotFound
is raised, it will be handled bycustom_handle_404()
, not bycustom_handle_not_found()
, becausecustom_handle_404()
was registered more recently.Note
By default, the framework installs three handlers, one for
HTTPError
, one forHTTPStatus
, and one for the standardException
type, which prevents passing uncaught exceptions to the WSGI server. These can be overridden by adding a custom error handler method for the exception type in question.When a generic unhandled exception is raised while handling a WebSocket connection, the default handler will close the connection with the standard close code
1011
(Internal Error). If your ASGI server does not support this code, the framework will use code3011
instead; or you can customize it via theerror_close_code
property ofws_options
.On the other hand, if an
on_websocket()
responder raises an instance ofHTTPError
, the default error handler will close the WebSocket connection with a framework close code derived by adding3000
to the HTTP status code (e.g.,3404
)- Parameters:
exception (type or iterable of types) – When handling a request, whenever an error occurs that is an instance of the specified type(s), the associated handler will be called. Either a single type or an iterable of types may be specified.
- Keyword Arguments:
handler (callable) –
A coroutine function taking the form:
async def func(req, resp, ex, params, ws=None): pass
In the case of a WebSocket connection, the resp argument will be
None
, while the ws keyword argument will receive theWebSocket
object representing the connection.If the handler keyword argument is not provided to
add_error_handler()
, the handler will default toexception.handle
, whereexception
is the error type specified above, andhandle
is a static method (i.e., decorated with@staticmethod
) that accepts the params just described. For example:class CustomException(CustomBaseException): @staticmethod async def handle(req, resp, ex, params): # TODO: Log the error # Convert to an instance of falcon.HTTPError raise falcon.HTTPError(falcon.HTTP_792)
Note, however, that if an iterable of exception types is specified instead of a single type, the handler must be explicitly specified using the handler keyword argument.
- add_route(uri_template, resource, **kwargs)[source]¶
Associate a templatized URI path with a resource.
Falcon routes incoming requests to resources based on a set of URI templates. If the path requested by the client matches the template for a given route, the request is then passed on to the associated resource for processing.
Note
If no route matches the request, control then passes to a default responder that simply raises an instance of
HTTPRouteNotFound
. By default, this error will be rendered as a 404 response, but this behavior can be modified by adding a custom error handler (see also this FAQ topic).On the other hand, if a route is matched but the resource does not implement a responder for the requested HTTP method, the framework invokes a default responder that raises an instance of
HTTPMethodNotAllowed
.This method delegates to the configured router’s
add_route()
method. To override the default behavior, pass a custom router object to theApp
initializer.(See also: Routing)
- Parameters:
uri_template (str) –
A templatized URI. Care must be taken to ensure the template does not mask any sink patterns, if any are registered.
(See also:
add_sink()
)Warning
If
strip_url_path_trailing_slash
is enabled, uri_template should be provided without a trailing slash.(See also: How does Falcon handle a trailing slash in the request path?)
resource (instance) –
Object which represents a REST resource. Falcon will pass GET requests to
on_get()
, PUT requests toon_put()
, etc. If any HTTP methods are not supported by your resource, simply don’t define the corresponding request handlers, and Falcon will do the right thing.Note
When using an async version of the
App
, all request handlers must be awaitable coroutine functions.
- Keyword Arguments:
suffix (str) –
Optional responder name suffix for this route. If a suffix is provided, Falcon will map GET requests to
on_get_{suffix}()
, POST requests toon_post_{suffix}()
, etc. In this way, multiple closely-related routes can be mapped to the same resource. For example, a single resource class can use suffixed responders to distinguish requests for a single item vs. a collection of those same items. Another class might use a suffixed responder to handle a shortlink route in addition to the regular route for the resource. For example:class Baz(object): def on_get_foo(self, req, resp): pass def on_get_bar(self, req, resp): pass baz = Baz() app = falcon.App() app.add_route('/foo', baz, suffix='foo') app.add_route('/bar', baz, suffix='bar')
compile (bool) – Optional flag that can be provided when using the default
CompiledRouter
to compile the routing logic on this call, since it will otherwise delay compilation until the first request is routed. SeeCompiledRouter.add_route()
for further details.
Note
Any additional keyword arguments not defined above are passed through to the underlying router’s
add_route()
method. The default router ignores any additional keyword arguments, but custom routers may take advantage of this feature to receive additional options when setting up routes. Custom routers MUST accept such arguments using the variadic pattern (**kwargs
), and ignore any keyword arguments that they don’t support.
- add_sink(sink, prefix='/')[source]¶
Register a sink method for the App.
If no route matches a request, but the path in the requested URI matches a sink prefix, Falcon will pass control to the associated sink, regardless of the HTTP method requested.
Using sinks, you can drain and dynamically handle a large number of routes, when creating static resources and responders would be impractical. For example, you might use a sink to create a smart proxy that forwards requests to one or more backend services.
- Parameters:
sink (callable) –
A callable taking the form
func(req, resp, **kwargs)
.Note
When using an async version of the
App
, this must be a coroutine.prefix (str) –
A regex string, typically starting with ‘/’, which will trigger the sink if it matches the path portion of the request’s URI. Both strings and precompiled regex objects may be specified. Characters are matched starting at the beginning of the URI path.
Note
Named groups are converted to kwargs and passed to the sink as such.
Warning
If the prefix overlaps a registered route template, the route will take precedence and mask the sink.
(See also:
add_route()
)
Options¶
- class falcon.RequestOptions[source]¶
Defines a set of configurable request options.
An instance of this class is exposed via
falcon.App.req_options
andfalcon.asgi.App.req_options
for configuring certainRequest
andfalcon.asgi.Request
behaviors, respectively.- keep_blank_qs_values¶
Set to
False
to ignore query string params that have missing or blank values (defaultTrue
). For comma-separated values, this option also determines whether or not empty elements in the parsed list are retained.- Type:
- auto_parse_form_urlencoded¶
Set to
True
in order to automatically consume the request stream and merge the results into the request’s query string params when the request’s content type is application/x-www-form-urlencoded (defaultFalse
).Enabling this option for WSGI apps makes the form parameters accessible via
params
,get_param()
, etc.Warning
The auto_parse_form_urlencoded option is not supported for ASGI apps, and is considered deprecated for WSGI apps as of Falcon 3.0, in favor of accessing URL-encoded forms through
media
.See also: How can I access POSTed form params?
Warning
When this option is enabled, the request’s body stream will be left at EOF. The original data is not retained by the framework.
Note
The character encoding for fields, before percent-encoding non-ASCII bytes, is assumed to be UTF-8. The special _charset_ field is ignored if present.
Falcon expects form-encoded request bodies to be encoded according to the standard W3C algorithm (see also http://goo.gl/6rlcux).
- auto_parse_qs_csv¶
Set to
True
to split query string values on any non-percent-encoded commas (defaultFalse
).When
False
, values containing commas are left as-is. In this mode, list items are taken only from multiples of the same parameter name within the query string (i.e.t=1,2,3&t=4
becomes['1,2,3', '4']
).When auto_parse_qs_csv is set to
True
, the query string value is also split on non-percent-encoded commas and these items are added to the final list (i.e.t=1,2,3&t=4,5
becomes['1', '2', '3', '4', '5']
).Warning
Enabling this option will cause the framework to misinterpret any JSON values that include literal (non-percent-encoded) commas. If the query string may include JSON, you can use JSON array syntax in lieu of CSV as a workaround.
- strip_url_path_trailing_slash¶
Set to
True
in order to strip the trailing slash, if present, at the end of the URL path (defaultFalse
). When this option is enabled, the URL path is normalized by stripping the trailing slash character. This lets the application define a single route to a resource for a path that may or may not end in a forward slash. However, this behavior can be problematic in certain cases, such as when working with authentication schemes that employ URL-based signatures.
- default_media_type¶
The default media-type used to deserialize a request body, when the Content-Type header is missing or ambiguous. This value is normally set to the media type provided to the
falcon.App
orfalcon.asgi.App
initializer; however, if created independently, this will default tofalcon.DEFAULT_MEDIA_TYPE
.- Type:
- class falcon.ResponseOptions[source]¶
Defines a set of configurable response options.
An instance of this class is exposed via
falcon.App.resp_options
andfalcon.asgi.App.resp_options
for configuring certainResponse
behaviors.- secure_cookies_by_default¶
Set to
False
in development environments to make the secure attribute for all cookies default toFalse
. This can make testing easier by not requiring HTTPS. Note, however, that this setting can be overridden via set_cookie()’s secure kwarg.- Type:
- default_media_type¶
The default Internet media type (RFC 2046) to use when rendering a response, when the Content-Type header is not set explicitly. This value is normally set to the media type provided when a
falcon.App
is initialized; however, if created independently, this will default tofalcon.DEFAULT_MEDIA_TYPE
..- Type:
- media_handlers¶
A dict-like object for configuring the media-types to handle. By default, handlers are provided for the
application/json
,application/x-www-form-urlencoded
andmultipart/form-data
media types.- Type:
- class falcon.routing.CompiledRouterOptions[source]
Defines a set of configurable router options.
An instance of this class is exposed via
falcon.App.router_options
andfalcon.asgi.App.router_options
for configuring certainCompiledRouter
behaviors.- converters
Represents the collection of named converters that may be referenced in URI template field expressions. Adding additional converters is simply a matter of mapping an identifier to a converter class:
app.router_options.converters['mc'] = MyConverter
The identifier can then be used to employ the converter within a URI template:
app.add_route('/{some_field:mc}', some_resource)
Converter names may only contain ASCII letters, digits, and underscores, and must start with either a letter or an underscore.
Warning
Converter instances are shared between requests. Therefore, in threaded deployments, care must be taken to implement custom converters in a thread-safe manner.
(See also: Field Converters)