Request & Response

Instances of the Request and Response classes are passed into responders as the second and third arguments, respectively.

import falcon


class Resource(object):

    def on_get(self, req, resp):
        resp.body = '{"message": "Hello world!"}'
        resp.status = falcon.HTTP_200

Request

class falcon.Request(env, options=None) [source]

Represents a client’s HTTP request.

Note

Request is not meant to be instantiated directly by responders.

Keyword Arguments:
Parameters:	env (dict) – A WSGI environment dict passed in from the server. See also PEP-3333.
	options (dict) – Set of global options passed from the API handler.

env

Reference to the WSGI environ dict passed in from the server. (See also PEP-3333.)

Type:	dict

context

Empty object to hold any data (in its attributes) about the request which is specific to your app (e.g. session object). Falcon itself will not interact with this attribute after it has been initialized.

Note

New in 2.0: the default context_type (see below) was changed from dict to a bare class, and the preferred way to pass request-specific data is now to set attributes directly on the context object, for example:

req.context.role = 'trial'
req.context.user = 'guest'

Type:	object

context_type

Class variable that determines the factory or type to use for initializing the context attribute. By default, the framework will instantiate bare objects (instances of the bare falcon.Context class). However, you may override this behavior by creating a custom child class of falcon.Request, and then passing that new class to falcon.API() by way of the latter’s request_type parameter.

Note

When overriding context_type with a factory function (as opposed to a class), the function is called like a method of the current Request instance. Therefore the first argument is the Request instance itself (self).

Type:	class

scheme

URL scheme used for the request. Either ‘http’ or ‘https’.

Note

If the request was proxied, the scheme may not match what was originally requested by the client. forwarded_scheme can be used, instead, to handle such cases.

Type:	str

forwarded_scheme

Original URL scheme requested by the user agent, if the request was proxied. Typical values are ‘http’ or ‘https’.

The following request headers are checked, in order of preference, to determine the forwarded scheme:

Forwarded
X-Forwarded-For

If none of these headers are available, or if the Forwarded header is available but does not contain a “proto” parameter in the first hop, the value of scheme is returned instead.

(See also: RFC 7239, Section 1)

Type:	str

method

HTTP method requested (e.g., ‘GET’, ‘POST’, etc.)

Type:	str

host

Host request header field

Type:	str

forwarded_host

Original host request header as received by the first proxy in front of the application server.

The following request headers are checked, in order of preference, to determine the forwarded scheme:

Forwarded
X-Forwarded-Host

If none of the above headers are available, or if the Forwarded header is available but the “host” parameter is not included in the first hop, the value of host is returned instead.

Note

Reverse proxies are often configured to set the Host header directly to the one that was originally requested by the user agent; in that case, using host is sufficient.

(See also: RFC 7239, Section 4)

Type:	str

port

Port used for the request. If the request URI does not specify a port, the default one for the given schema is returned (80 for HTTP and 443 for HTTPS).

Type:	int

netloc

Returns the ‘host:port’ portion of the request URL. The port may be ommitted if it is the default one for the URL’s schema (80 for HTTP and 443 for HTTPS).

Type:	str

subdomain

Leftmost (i.e., most specific) subdomain from the hostname. If only a single domain name is given, subdomain will be None.

Note

If the hostname in the request is an IP address, the value for subdomain is undefined.

Type:	str

app

The initial portion of the request URI’s path that corresponds to the application object, so that the application knows its virtual “location”. This may be an empty string, if the application corresponds to the “root” of the server.

(Corresponds to the “SCRIPT_NAME” environ variable defined by PEP-3333.)

Type:	str

uri

The fully-qualified URI for the request.

Type:	str

url

Alias for uri.

Type:	str

forwarded_uri

Original URI for proxied requests. Uses forwarded_scheme and forwarded_host in order to reconstruct the original URI requested by the user agent.

Type:	str

relative_uri

The path and query string portion of the request URI, omitting the scheme and host.

Type:	str

prefix

The prefix of the request URI, including scheme, host, and WSGI app (if any).

Type:	str

forwarded_prefix

The prefix of the original URI for proxied requests. Uses forwarded_scheme and forwarded_host in order to reconstruct the original URI.

Type:	str

path

Path portion of the request URI (not including query string).

Note

req.path may be set to a new value by a process_request() middleware method in order to influence routing. If the original request path was URL encoded, it will be decoded before being returned by this attribute. If this attribute is to be used by the app for any upstream requests, any non URL-safe characters in the path must be URL encoded back before making the request.

Type:	str

query_string

Query string portion of the request URI, without the preceding ‘?’ character.

Type:	str

uri_template

The template for the route that was matched for this request. May be None if the request has not yet been routed, as would be the case for process_request() middleware methods. May also be None if your app uses a custom routing engine and the engine does not provide the URI template when resolving a route.

Type:	str

remote_addr

IP address of the closest client or proxy to the WSGI server.

This property is determined by the value of REMOTE_ADDR in the WSGI environment dict. Since this address is not derived from an HTTP header, clients and proxies can not forge it.

Note

If your application is behind one or more reverse proxies, you can use access_route to retrieve the real IP address of the client.

Type:	str

access_route

IP address of the original client, as well as any known addresses of proxies fronting the WSGI server.

The following request headers are checked, in order of preference, to determine the addresses:

Forwarded
X-Forwarded-For
X-Real-IP

If none of these headers are available, the value of remote_addr is used instead.

Note

Per RFC 7239, the access route may contain “unknown” and obfuscated identifiers, in addition to IPv4 and IPv6 addresses

Warning

Headers can be forged by any client or proxy. Use this property with caution and validate all values before using them. Do not rely on the access route to authorize requests.

Type:	list

forwarded

Value of the Forwarded header, as a parsed list of falcon.Forwarded objects, or None if the header is missing. If the header value is malformed, Falcon will make a best effort to parse what it can.

(See also: RFC 7239, Section 4)

Type:	list

date

Value of the Date header, converted to a datetime instance. The header value is assumed to conform to RFC 1123.

Type:	datetime

auth

Value of the Authorization header, or None if the header is missing.

Type:	str

user_agent

Value of the User-Agent header, or None if the header is missing.

Type:	str

referer

Value of the Referer header, or None if the header is missing.

Type:	str

accept

Value of the Accept header, or ‘/’ if the header is missing.

Type:	str

client_accepts_json

True if the Accept header indicates that the client is willing to receive JSON, otherwise False.

Type:	bool

client_accepts_msgpack

True if the Accept header indicates that the client is willing to receive MessagePack, otherwise False.

Type:	bool

client_accepts_xml

True if the Accept header indicates that the client is willing to receive XML, otherwise False.

Type:	bool

cookies

A dict of name/value cookie pairs. The returned object should be treated as read-only to avoid unintended side-effects. If a cookie appears more than once in the request, only the first value encountered will be made available here.

See also: get_cookie_values()

Type:	dict

content_type

Value of the Content-Type header, or None if the header is missing.

Type:	str

content_length

Value of the Content-Length header converted to an int, or None if the header is missing.

Type:	int

stream

File-like input object for reading the body of the request, if any. This object provides direct access to the server’s data stream and is non-seekable. In order to avoid unintended side effects, and to provide maximum flexibility to the application, Falcon itself does not buffer or spool the data in any way.

Since this object is provided by the WSGI server itself, rather than by Falcon, it may behave differently depending on how you host your app. For example, attempting to read more bytes than are expected (as determined by the Content-Length header) may or may not block indefinitely. It’s a good idea to test your WSGI server to find out how it behaves.

This can be particulary problematic when a request body is expected, but none is given. In this case, the following call blocks under certain WSGI servers:

# Blocks if Content-Length is 0
data = req.stream.read()

The workaround is fairly straightforward, if verbose:

# If Content-Length happens to be 0, or the header is
# missing altogether, this will not block.
data = req.stream.read(req.content_length or 0)

Alternatively, when passing the stream directly to a consumer, it may be necessary to branch off the value of the Content-Length header:

if req.content_length:
    doc = json.load(req.stream)

For a slight performance cost, you may instead wish to use bounded_stream, which wraps the native WSGI input object to normalize its behavior.

Note

If an HTML form is POSTed to the API using the application/x-www-form-urlencoded media type, and the auto_parse_form_urlencoded option is set, the framework will consume stream in order to parse the parameters and merge them into the query string parameters. In this case, the stream will be left at EOF.

bounded_stream

File-like wrapper around stream to normalize certain differences between the native input objects employed by different WSGI servers. In particular, bounded_stream is aware of the expected Content-Length of the body, and will never block on out-of-bounds reads, assuming the client does not stall while transmitting the data to the server.

For example, the following will not block when Content-Length is 0 or the header is missing altogether:

data = req.bounded_stream.read()

This is also safe:

doc = json.load(req.bounded_stream)

expect

Value of the Expect header, or None if the header is missing.

Type:	str

media

Returns a deserialized form of the request stream. When called, it will attempt to deserialize the request stream using the Content-Type header as well as the media-type handlers configured via falcon.RequestOptions.

See Media for more information regarding media handling.

Warning

This operation will consume the request stream the first time it’s called and cache the results. Follow-up calls will just retrieve a cached version of the object.

Type:	object

range

A 2-member tuple parsed from the value of the Range header.

The two members correspond to the first and last byte positions of the requested resource, inclusive. Negative indices indicate offset from the end of the resource, where -1 is the last byte, -2 is the second-to-last byte, and so forth.

Only continous ranges are supported (e.g., “bytes=0-0,-1” would result in an HTTPBadRequest exception when the attribute is accessed.)

Type:	tuple of int

range_unit

Unit of the range parsed from the value of the Range header, or None if the header is missing

Type:	str

if_match

Value of the If-Match header, as a parsed list of falcon.ETag objects or None if the header is missing or its value is blank.

This property provides a list of all entity-tags in the header, both strong and weak, in the same order as listed in the header.

(See also: RFC 7232, Section 3.1)

Type:	list

if_none_match

Value of the If-None-Match header, as a parsed list of falcon.ETag objects or None if the header is missing or its value is blank.

This property provides a list of all entity-tags in the header, both strong and weak, in the same order as listed in the header.

(See also: RFC 7232, Section 3.2)

Type:	list

if_modified_since

Value of the If-Modified-Since header, or None if the header is missing.

Type:	datetime

if_unmodified_since

Value of the If-Unmodified-Since header, or None if the header is missing.

Type:	datetime

if_range

Value of the If-Range header, or None if the header is missing.

Type:	str

headers

Raw HTTP headers from the request with canonical dash-separated names. Parsing all the headers to create this dict is done the first time this attribute is accessed, and the returned object should be treated as read-only. Note that this parsing can be costly, so unless you need all the headers in this format, you should instead use the get_header() method or one of the convenience attributes to get a value for a specific header.

Type:	dict

params

The mapping of request query parameter names to their values. Where the parameter appears multiple times in the query string, the value mapped to that parameter key will be a list of all the values in the order seen.

Type:	dict

options

Set of global options passed from the API handler.

Type:	dict

client_accepts(media_type) [source]

Determine whether or not the client accepts a given media type.

Parameters:	media_type (str) – An Internet media type to check.
Returns:	`True` if the client has indicated in the Accept header that it accepts the specified media type. Otherwise, returns `False`.
Return type:	bool

client_prefers(media_types) [source]

Return the client’s preferred media type, given several choices.

Parameters:	media_types (iterable of str) – One or more Internet media types from which to choose the client’s preferred type. This value must be an iterable collection of strings.
Returns:	The client’s preferred media type, based on the Accept header. Returns `None` if the client does not accept any of the given types.
Return type:	str

context_type: alias of falcon.util.structures.Context

get_cookie_values(name) [source]

Return all values provided in the Cookie header for the named cookie.

(See also: Getting Cookies)

Parameters:	name (str) – Cookie name, case-sensitive.
Returns:	Ordered list of all values specified in the Cookie header for the named cookie, or `None` if the cookie was not included in the request. If the cookie is specified more than once in the header, the returned list of values will preserve the ordering of the individual `cookie-pair`’s in the header.
Return type:	list

get_header(name, required=False, default=None) [source]

Retrieve the raw string value for the given header.

Keyword Arguments:
Parameters:	name (str) – Header name, case-insensitive (e.g., ‘Content-Type’)
	required (bool) – Set to `True` to raise `HTTPBadRequest` instead of returning gracefully when the header is not found (default `False`). default (any) – Value to return if the header is not found (default `None`).
Returns:	The value of the specified header if it exists, or the default value if the header is not found and is not required.
Return type:	str
Raises:	`HTTPBadRequest` – The header was not found in the request, but it was required.

get_header_as_datetime(header, required=False, obs_date=False) [source]

Return an HTTP header with HTTP-Date values as a datetime.

Keyword Arguments:
Parameters:	name (str) – Header name, case-insensitive (e.g., ‘Date’)
	required (bool) – Set to `True` to raise `HTTPBadRequest` instead of returning gracefully when the header is not found (default `False`). obs_date (bool) – Support obs-date formats according to RFC 7231, e.g.: “Sunday, 06-Nov-94 08:49:37 GMT” (default `False`).
Returns:	The value of the specified header if it exists, or `None` if the header is not found and is not required.
Return type:	datetime
Raises:	`HTTPBadRequest` – The header was not found in the request, but it was required. `HttpInvalidHeader` – The header contained a malformed/invalid value.

get_param(name, required=False, store=None, default=None) [source]

Return the raw value of a query string parameter as a string.

Note

If an HTML form is POSTed to the API using the application/x-www-form-urlencoded media type, Falcon can automatically parse the parameters from the request body and merge them into the query string parameters. To enable this functionality, set auto_parse_form_urlencoded to True via API.req_options.

Note

Similar to the way multiple keys in form data is handled, if a query parameter is assigned a comma-separated list of values (e.g., foo=a,b,c), only one of those values will be returned, and it is undefined which one. Use get_param_as_list() to retrieve all the values.

Keyword Arguments:
Parameters:	name (str) – Parameter name, case-sensitive (e.g., ‘sort’).
	required (bool) – Set to `True` to raise `HTTPBadRequest` instead of returning `None` when the parameter is not found (default `False`). store (dict) – A `dict`-like object in which to place the value of the param, but only if the param is present. default (any) – If the param is not found returns the given value instead of `None`
Returns:	The value of the param as a string, or `None` if param is not found and is not required.
Return type:	str
Raises:	`HTTPBadRequest` – A required param is missing from the request.

get_param_as_bool(name, required=False, store=None, blank_as_true=True, default=None) [source]

Return the value of a query string parameter as a boolean.

This method treats valueless parameters as flags. By default, if no value is provided for the parameter in the query string, True is assumed and returned. If the parameter is missing altogether, None is returned as with other get_param_*() methods, which can be easily treated as falsy by the caller as needed.

The following boolean strings are supported:

TRUE_STRINGS = ('true', 'True', 'yes', '1', 'on')
FALSE_STRINGS = ('false', 'False', 'no', '0', 'off')

Keyword Arguments:
Parameters:	name (str) – Parameter name, case-sensitive (e.g., ‘detailed’).
	required (bool) – Set to `True` to raise `HTTPBadRequest` instead of returning `None` when the parameter is not found or is not a recognized boolean string (default `False`). store (dict) – A `dict`-like object in which to place the value of the param, but only if the param is found (default `None`). blank_as_true (bool) – Valueless query string parameters are treated as flags, resulting in `True` being returned when such a parameter is present, and `False` otherwise. To require the client to explicitly opt-in to a truthy value, pass `blank_as_true=False` to return `False` when a value is not specified in the query string. default (any) – If the param is not found, return this value instead of `None`.
Returns:	The value of the param if it is found and can be converted to a `bool`. If the param is not found, returns `None` unless `required` is `True`.
Return type:	bool
Raises:	`HTTPBadRequest` – A required param is missing from the request, or can not be converted to a `bool`.

get_param_as_date(name, format_string='%Y-%m-%d', required=False, store=None, default=None) [source]

Return the value of a query string parameter as a date.

Keyword Arguments:
Parameters:	name (str) – Parameter name, case-sensitive (e.g., ‘ids’).
	format_string (str) – String used to parse the param value into a date. Any format recognized by strptime() is supported (default `"%Y-%m-%d"`). required (bool) – Set to `True` to raise `HTTPBadRequest` instead of returning `None` when the parameter is not found (default `False`). store (dict) – A `dict`-like object in which to place the value of the param, but only if the param is found (default `None`). default (any) – If the param is not found returns the given value instead of `None`
Returns:	The value of the param if it is found and can be converted to a `date` according to the supplied format string. If the param is not found, returns `None` unless required is `True`.
Return type:	datetime.date
Raises:	`HTTPBadRequest` – A required param is missing from the request, or the value could not be converted to a `date`.

get_param_as_datetime(name, format_string='%Y-%m-%dT%H:%M:%SZ', required=False, store=None, default=None) [source]

Return the value of a query string parameter as a datetime.

Keyword Arguments:
Parameters:	name (str) – Parameter name, case-sensitive (e.g., ‘ids’).
	format_string (str) – String used to parse the param value into a `datetime`. Any format recognized by strptime() is supported (default `'%Y-%m-%dT%H:%M:%SZ'`). required (bool) – Set to `True` to raise `HTTPBadRequest` instead of returning `None` when the parameter is not found (default `False`). store (dict) – A `dict`-like object in which to place the value of the param, but only if the param is found (default `None`). default (any) – If the param is not found returns the given value instead of `None`
Returns:	The value of the param if it is found and can be converted to a `datetime` according to the supplied format string. If the param is not found, returns `None` unless required is `True`.
Return type:	datetime.datetime
Raises:	`HTTPBadRequest` – A required param is missing from the request, or the value could not be converted to a `datetime`.

get_param_as_float(name, required=False, min_value=None, max_value=None, store=None, default=None) [source]

Return the value of a query string parameter as an float.

Keyword Arguments:
Parameters:	name (str) – Parameter name, case-sensitive (e.g., ‘limit’).
	required (bool) – Set to `True` to raise `HTTPBadRequest` instead of returning `None` when the parameter is not found or is not an float (default `False`). min_value (float) – Set to the minimum value allowed for this param. If the param is found and it is less than min_value, an `HTTPError` is raised. max_value (float) – Set to the maximum value allowed for this param. If the param is found and its value is greater than max_value, an `HTTPError` is raised. store (dict) – A `dict`-like object in which to place the value of the param, but only if the param is found (default `None`). default (any) – If the param is not found returns the given value instead of `None`
Returns:	The value of the param if it is found and can be converted to an `float`. If the param is not found, returns `None`, unless `required` is `True`.
Return type:	float

Raises

HTTPBadRequest: The param was not found in the request, even though: it was required to be there, or it was found but could not be converted to an float. Also raised if the param’s value falls outside the given interval, i.e., the value must be in the interval: min_value <= value <= max_value to avoid triggering an error.

get_param_as_int(name, required=False, min_value=None, max_value=None, store=None, default=None) [source]

Return the value of a query string parameter as an int.

Keyword Arguments:
Parameters:	name (str) – Parameter name, case-sensitive (e.g., ‘limit’).
	required (bool) – Set to `True` to raise `HTTPBadRequest` instead of returning `None` when the parameter is not found or is not an integer (default `False`). min_value (int) – Set to the minimum value allowed for this param. If the param is found and it is less than min_value, an `HTTPError` is raised. max_value (int) – Set to the maximum value allowed for this param. If the param is found and its value is greater than max_value, an `HTTPError` is raised. store (dict) – A `dict`-like object in which to place the value of the param, but only if the param is found (default `None`). default (any) – If the param is not found returns the given value instead of `None`
Returns:	The value of the param if it is found and can be converted to an `int`. If the param is not found, returns `None`, unless `required` is `True`.
Return type:	int

Raises

HTTPBadRequest: The param was not found in the request, even though: it was required to be there, or it was found but could not be converted to an int. Also raised if the param’s value falls outside the given interval, i.e., the value must be in the interval: min_value <= value <= max_value to avoid triggering an error.

get_param_as_json(name, required=False, store=None, default=None) [source]

Return the decoded JSON value of a query string parameter.

Given a JSON value, decode it to an appropriate Python type, (e.g., dict, list, str, int, bool, etc.)

Keyword Arguments:
Parameters:	name (str) – Parameter name, case-sensitive (e.g., ‘payload’).
	required (bool) – Set to `True` to raise `HTTPBadRequest` instead of returning `None` when the parameter is not found (default `False`). store (dict) – A `dict`-like object in which to place the value of the param, but only if the param is found (default `None`). default (any) – If the param is not found returns the given value instead of `None`
Returns:	The value of the param if it is found. Otherwise, returns `None` unless required is `True`.
Return type:	dict
Raises:	`HTTPBadRequest` – A required param is missing from the request, or the value could not be parsed as JSON.

get_param_as_list(name, transform=None, required=False, store=None, default=None) [source]

Return the value of a query string parameter as a list.

List items must be comma-separated or must be provided as multiple instances of the same param in the query string ala application/x-www-form-urlencoded.

Keyword Arguments:
Parameters:	name (str) – Parameter name, case-sensitive (e.g., ‘ids’).
	transform (callable) – An optional transform function that takes as input each element in the list as a `str` and outputs a transformed element for inclusion in the list that will be returned. For example, passing `int` will transform list items into numbers. required (bool) – Set to `True` to raise `HTTPBadRequest` instead of returning `None` when the parameter is not found (default `False`). store (dict) – A `dict`-like object in which to place the value of the param, but only if the param is found (default `None`). default (any) – If the param is not found returns the given value instead of `None`
Returns:	The value of the param if it is found. Otherwise, returns `None` unless required is True. Empty list elements will be discarded. For example, the following query strings would both result in `[‘1’, ‘3’]`: things=1,,3 things=1&things=&things=3
Return type:	list
Raises:	`HTTPBadRequest` – A required param is missing from the request, or a transform function raised an instance of `ValueError`.

get_param_as_uuid(name, required=False, store=None, default=None) [source]

Return the value of a query string parameter as an UUID.

The value to convert must conform to the standard UUID string representation per RFC 4122. For example, the following strings are all valid:

# Lowercase
'64be949b-3433-4d36-a4a8-9f19d352fee8'

# Uppercase
'BE71ECAA-F719-4D42-87FD-32613C2EEB60'

# Mixed
'81c8155C-D6de-443B-9495-39Fa8FB239b5'

Keyword Arguments:
Parameters:	name (str) – Parameter name, case-sensitive (e.g., ‘id’).
	required (bool) – Set to `True` to raise `HTTPBadRequest` instead of returning `None` when the parameter is not found or is not a UUID (default `False`). store (dict) – A `dict`-like object in which to place the value of the param, but only if the param is found (default `None`). default (any) – If the param is not found returns the given value instead of `None`
Returns:	The value of the param if it is found and can be converted to a `UUID`. If the param is not found, returns `default` (default `None`), unless `required` is `True`.
Return type:	UUID

Raises

HTTPBadRequest: The param was not found in the request, even though: it was required to be there, or it was found but could not be converted to a UUID.

has_param(name) [source]

Determine whether or not the query string parameter already exists.

Parameters:	name (str) – Parameter name, case-sensitive (e.g., ‘sort’).
Returns:	`True` if param is found, or `False` if param is not found.
Return type:	bool

log_error(message) [source]

Write an error message to the server’s log.

Prepends timestamp and request info to message, and writes the result out to the WSGI server’s error stream (wsgi.error).

Parameters:	message (str or unicode) – Description of the problem. On Python 2, instances of `unicode` will be converted to UTF-8.

class falcon.Forwarded [source]

Represents a parsed Forwarded header.

(See also: RFC 7239, Section 4)

src

The value of the “for” parameter, or None if the parameter is absent. Identifies the node making the request to the proxy.

Type:	str

dest

The value of the “by” parameter, or None if the parameter is absent. Identifies the client-facing interface of the proxy.

Type:	str

host

The value of the “host” parameter, or None if the parameter is absent. Provides the host request header field as received by the proxy.

Type:	str

scheme

The value of the “proto” parameter, or None if the parameter is absent. Indicates the protocol that was used to make the request to the proxy.

Type:	str

Response

class falcon.Response(options=None) [source]

Represents an HTTP response to a client request.

Note

Response is not meant to be instantiated directly by responders.

Keyword Arguments:
	options (dict) – Set of global options passed from the API handler.

status

HTTP status line (e.g., ‘200 OK’). Falcon requires the full status line, not just the code (e.g., 200). This design makes the framework more efficient because it does not have to do any kind of conversion or lookup when composing the WSGI response.

If not set explicitly, the status defaults to ‘200 OK’.

Note

Falcon provides a number of constants for common status codes. They all start with the HTTP_ prefix, as in: falcon.HTTP_204.

Type:	str

media

A serializable object supported by the media handlers configured via falcon.RequestOptions.

See Media for more information regarding media handling.

Type:	object

body

String representing response content.

If set to a Unicode type (unicode in Python 2, or str in Python 3), Falcon will encode the text as UTF-8 in the response. If the content is already a byte string, use the data attribute instead (it’s faster).

Type:	str or unicode

data

Byte string representing response content.

Use this attribute in lieu of body when your content is already a byte string (str or bytes in Python 2, or simply bytes in Python 3). See also the note below.

Note

Under Python 2.x, if your content is of type str, using the data attribute instead of body is the most efficient approach. However, if your text is of type unicode, you will need to use the body attribute instead.

Under Python 3.x, on the other hand, the 2.x str type can be thought of as having been replaced by what was once the unicode type, and so you will need to always use the body attribute for strings to ensure Unicode characters are properly encoded in the HTTP response.

Type:	bytes

stream: Either a file-like object with a read() method that takes an optional size argument and returns a block of bytes, or an iterable object, representing response content, and yielding blocks as byte strings. Falcon will use wsgi.file_wrapper, if provided by the WSGI server, in order to efficiently serve file-like objects.

Note

If the stream is set to an iterable object that requires resource cleanup, it can implement a close() method to do so. The close() method will be called upon completion of the request.

stream_len

Deprecated alias for content_length.

Type:	int

context

Dictionary to hold any data about the response which is specific to your app. Falcon itself will not interact with this attribute after it has been initialized.

Type:	dict

context

Empty object to hold any data (in its attributes) about the response which is specific to your app (e.g. session object). Falcon itself will not interact with this attribute after it has been initialized.

Note

New in 2.0: the default context_type (see below) was changed from dict to a bare class, and the preferred way to pass response-specific data is now to set attributes directly on the context object, for example:

resp.context.cache_strategy = 'lru'

Type:	object

context_type

Class variable that determines the factory or type to use for initializing the context attribute. By default, the framework will instantiate bare objects (instances of the bare falcon.Context class). However, you may override this behavior by creating a custom child class of falcon.Response, and then passing that new class to falcon.API() by way of the latter’s response_type parameter.

Note

When overriding context_type with a factory function (as opposed to a class), the function is called like a method of the current Response instance. Therefore the first argument is the Response instance itself (self).

Type:	class

options

Set of global options passed from the API handler.

Type:	dict

headers

Copy of all headers set for the response, sans cookies. Note that a new copy is created and returned each time this property is referenced.

Type:	dict

complete

Set to True from within a middleware method to signal to the framework that request processing should be short-circuited (see also Middleware).

Type:	bool

accept_ranges

Set the Accept-Ranges header.

The Accept-Ranges header field indicates to the client which range units are supported (e.g. “bytes”) for the target resource.

If range requests are not supported for the target resource, the header may be set to “none” to advise the client not to attempt any such requests.

Note

“none” is the literal string, not Python’s built-in None type.

add_link(target, rel, title=None, title_star=None, anchor=None, hreflang=None, type_hint=None) [source]

Add a link header to the response.

(See also: RFC 5988, Section 1)

Note

Calling this method repeatedly will cause each link to be appended to the Link header value, separated by commas.

Note

So-called “link-extension” elements, as defined by RFC 5988, are not yet supported. See also Issue #288.

Parameters:

target (str) – Target IRI for the resource identified by the link. Will be converted to a URI, if necessary, per RFC 3987, Section 3.1.
rel (str) –
Relation type of the link, such as “next” or “bookmark”.

(See also: http://www.iana.org/assignments/link-relations/link-relations.xhtml)

Keyword Arguments:

title (str) – Human-readable label for the destination of the link (default None). If the title includes non-ASCII characters, you will need to use title_star instead, or provide both a US-ASCII version using title and a Unicode version using title_star.
title_star (tuple of str) –
Localized title describing the destination of the link (default None). The value must be a two-member tuple in the form of (language-tag, text), where language-tag is a standard language identifier as defined in RFC 5646, Section 2.1, and text is a Unicode string.

Note

language-tag may be an empty string, in which case the client will assume the language from the general context of the current request.

Note

text will always be encoded as UTF-8. If the string contains non-ASCII characters, it should be passed as a unicode type string (requires the ‘u’ prefix in Python 2).
anchor (str) – Override the context IRI with a different URI (default None). By default, the context IRI for the link is simply the IRI of the requested resource. The value provided may be a relative URI.
hreflang (str or iterable) – Either a single language-tag, or a list or tuple of such tags to provide a hint to the client as to the language of the result of following the link. A list of tags may be given in order to indicate to the client that the target resource is available in multiple languages.
type_hint (str) – Provides a hint as to the media type of the result of dereferencing the link (default None). As noted in RFC 5988, this is only a hint and does not override the Content-Type header returned when the link is followed.

append_header(name, value) [source]

Set or append a header for this response.

If the header already exists, the new value will normally be appended to it, delimited by a comma. The notable exception to this rule is Set-Cookie, in which case a separate header line for each value will be included in the response.

Note

While this method can be used to efficiently append raw Set-Cookie headers to the response, you may find set_cookie() to be more convenient.

Parameters:	name (str) – Header name (case-insensitive). The restrictions noted below for the header’s value also apply here. value (str) – Value for the header. Must be convertable to `str` or be of type `str` or `StringType`. Strings must contain only US-ASCII characters. Under Python 2.x, the `unicode` type is also accepted, although such strings are also limited to US-ASCII.

cache_control

Set the Cache-Control header.

Used to set a list of cache directives to use as the value of the Cache-Control header. The list will be joined with “, ” to produce the value for the header.

content_length

Set the Content-Length header.

This property can be used for responding to HEAD requests when you aren’t actually providing the response body, or when streaming the response. If either the body property or the data property is set on the response, the framework will force Content-Length to be the length of the given body bytes. Therefore, it is only necessary to manually set the content length when those properties are not used.

Note

In cases where the response content is a stream (readable file-like object), Falcon will not supply a Content-Length header to the WSGI server unless content_length is explicitly set. Consequently, the server may choose to use chunked encoding or one of the other strategies suggested by PEP-3333.

content_location

Set the Content-Location header.

This value will be URI encoded per RFC 3986. If the value that is being set is already URI encoded it should be decoded first or the header should be set manually using the set_header method.

content_range

A tuple to use in constructing a value for the Content-Range header.

The tuple has the form (start, end, length, [unit]), where start and end designate the range (inclusive), and length is the total length, or ‘*’ if unknown. You may pass int’s for these numbers (no need to convert to str beforehand). The optional value unit describes the range unit and defaults to ‘bytes’

Note

You only need to use the alternate form, ‘bytes */1234’, for responses that use the status ‘416 Range Not Satisfiable’. In this case, raising falcon.HTTPRangeNotSatisfiable will do the right thing.

(See also: RFC 7233, Section 4.2)

content_type

Sets the Content-Type header.

The falcon module provides a number of constants for common media types, including falcon.MEDIA_JSON, falcon.MEDIA_MSGPACK, falcon.MEDIA_YAML, falcon.MEDIA_XML, falcon.MEDIA_HTML, falcon.MEDIA_JS, falcon.MEDIA_TEXT, falcon.MEDIA_JPEG, falcon.MEDIA_PNG, and falcon.MEDIA_GIF.

context_type: alias of falcon.util.structures.Context

delete_header(name) [source]

Delete a header that was previously set for this response.

If the header was not previously set, nothing is done (no error is raised). Otherwise, all values set for the header will be removed from the response.

Note that calling this method is equivalent to setting the corresponding header property (when said property is available) to None. For example:

resp.etag = None

Warning

This method cannot be used with the Set-Cookie header. Instead, use unset_cookie() to remove a cookie and ensure that the user agent expires its own copy of the data as well.

Parameters:	name (str) – Header name (case-insensitive). Must be of type `str` or `StringType` and contain only US-ASCII characters. Under Python 2.x, the `unicode` type is also accepted, although such strings are also limited to US-ASCII.
Raises:	`ValueError` – `name` cannot be `'Set-Cookie'`.

downloadable_as

Set the Content-Disposition header using the given filename.

The value will be used for the filename directive. For example, given 'report.pdf', the Content-Disposition header would be set to: 'attachment; filename="report.pdf"'.

etag

Set the ETag header.

The ETag header will be wrapped with double quotes "value" in case the user didn’t pass it.

expires: Set the Expires header. Set to a datetime (UTC) instance.

Note

Falcon will format the datetime as an HTTP date string.

get_header(name, default=None) [source]

Retrieve the raw string value for the given header.

Normally, when a header has multiple values, they will be returned as a single, comma-delimited string. However, the Set-Cookie header does not support this format, and so attempting to retrieve it will raise an error.

Keyword Arguments:
Parameters:	name (str) – Header name, case-insensitive. Must be of type `str` or `StringType`, and only character values 0x00 through 0xFF may be used on platforms that use wide characters.
	default – Value to return if the header is not found (default `None`).
Raises:	`ValueError` – The value of the ‘Set-Cookie’ header(s) was requested.
Returns:	The value of the specified header if set, or the default value if not set.
Return type:	str

last_modified: Set the Last-Modified header. Set to a datetime (UTC) instance.

Note

Falcon will format the datetime as an HTTP date string.

location

Set the Location header.

This value will be URI encoded per RFC 3986. If the value that is being set is already URI encoded it should be decoded first or the header should be set manually using the set_header method.

retry_after

Set the Retry-After header.

The expected value is an integral number of seconds to use as the value for the header. The HTTP-date syntax is not supported.

set_cookie(name, value, expires=None, max_age=None, domain=None, path=None, secure=None, http_only=True) [source]

Set a response cookie.

Note

This method can be called multiple times to add one or more cookies to the response.

Keyword Arguments:
Parameters:	name (str) – Cookie name value (str) – Cookie value
	expires (datetime) – Specifies when the cookie should expire. By default, cookies expire when the user agent exits. (See also: RFC 6265, Section 4.1.2.1) max_age (int) – Defines the lifetime of the cookie in seconds. By default, cookies expire when the user agent exits. If both `max_age` and `expires` are set, the latter is ignored by the user agent. Note Coercion to `int` is attempted if provided with `float` or `str`. (See also: RFC 6265, Section 4.1.2.2) domain (str) – Restricts the cookie to a specific domain and any subdomains of that domain. By default, the user agent will return the cookie only to the origin server. When overriding this default behavior, the specified domain must include the origin server. Otherwise, the user agent will reject the cookie. (See also: RFC 6265, Section 4.1.2.3) path (str) – Scopes the cookie to the given path plus any subdirectories under that path (the “/” character is interpreted as a directory separator). If the cookie does not specify a path, the user agent defaults to the path component of the requested URI. Warning User agent interfaces do not always isolate cookies by path, and so this should not be considered an effective security measure. (See also: RFC 6265, Section 4.1.2.4) secure (bool) – Direct the client to only return the cookie in subsequent requests if they are made over HTTPS (default: `True`). This prevents attackers from reading sensitive cookie data. Note The default value for this argument is normally `True`, but can be modified by setting `secure_cookies_by_default` via `API.resp_options`. Warning For the `secure` cookie attribute to be effective, your application will need to enforce HTTPS. (See also: RFC 6265, Section 4.1.2.5) http_only (bool) – Direct the client to only transfer the cookie with unscripted HTTP requests (default: `True`). This is intended to mitigate some forms of cross-site scripting. (See also: RFC 6265, Section 4.1.2.6)
Raises:	`KeyError` – `name` is not a valid cookie name. `ValueError` – `value` is not a valid cookie value.

Parameters:	headers (dict or list) – A dictionary of header names and values to set, or a `list` of (name, value) tuples. Both name and value must be of type `str` or `StringType` and contain only US-ASCII characters. Under Python 2.x, the `unicode` type is also accepted, although such strings are also limited to US-ASCII. Note Falcon can process a list of tuples slightly faster than a dict.
Raises:	`ValueError` – `headers` was not a `dict` or `list` of `tuple`.