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
class falcon.Request(env, options=None)
[source]
Represents a client’s HTTP request.
Note
Request
is not meant to be instantiated directly by responders.
Parameters: | env (dict) – A WSGI environment dict passed in from the server. See also PEP-3333. |
---|---|
Keyword Arguments: | |
options (dict) – Set of global options passed from the API handler. |
env
dict – Reference to the WSGI environ dict
passed in from the server. (See also PEP-3333.)
context
dict – Dictionary to hold any data 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.
context_type
class – Class variable that determines the factory or type to use for initializing the context
attribute. By default, the framework will instantiate standard dict
objects. 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).
scheme
str – 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.
forwarded_scheme
str – 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)
protocol
str – Deprecated alias for scheme
. Will be removed in a future release.
method
str – HTTP method requested (e.g., ‘GET’, ‘POST’, etc.)
host
str – Host request header field
forwarded_host
str – 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)
port
int – 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).
netloc
str – 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).
subdomain
str – 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.
app
str – 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.)
uri
str – The fully-qualified URI for the request.
url
str – Alias for uri
.
forwarded_uri
str – Original URI for proxied requests. Uses forwarded_scheme
and forwarded_host
in order to reconstruct the original URI requested by the user agent.
relative_uri
str – The path and query string portion of the request URI, omitting the scheme and host.
prefix
str – The prefix of the request URI, including scheme, host, and WSGI app (if any).
forwarded_prefix
str – The prefix of the original URI for proxied requests. Uses forwarded_scheme
and forwarded_host
in order to reconstruct the original URI.
path
str – 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.
query_string
str – Query string portion of the request URI, without the preceding ‘?’ character.
uri_template
str – 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.
remote_addr
str – 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.
access_route
list – 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.
forwarded
list – 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)
date
datetime – Value of the Date header, converted to a datetime
instance. The header value is assumed to conform to RFC 1123.
auth
str – Value of the Authorization header, or None
if the header is missing.
user_agent
str – Value of the User-Agent header, or None
if the header is missing.
referer
str – Value of the Referer header, or None
if the header is missing.
accept
str – Value of the Accept header, or ‘/’ if the header is missing.
client_accepts_json
bool – True
if the Accept header indicates that the client is willing to receive JSON, otherwise False
.
client_accepts_msgpack
bool – True
if the Accept header indicates that the client is willing to receive MessagePack, otherwise False
.
client_accepts_xml
bool – True
if the Accept header indicates that the client is willing to receive XML, otherwise False
.
dict – A dict of name/value cookie pairs. (See also: Getting Cookies)
content_type
str – Value of the Content-Type header, or None
if the header is missing.
content_length
int – Value of the Content-Length header converted to an int
, or None
if the header is missing.
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
str – Value of the Expect header, or None
if the header is missing.
media
object – 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.
range
tuple of int – 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.)
range_unit
str – Unit of the range parsed from the value of the Range header, or None
if the header is missing
if_match
str – Value of the If-Match header, or None
if the header is missing.
if_none_match
str – Value of the If-None-Match header, or None
if the header is missing.
if_modified_since
datetime – Value of the If-Modified-Since header, or None
if the header is missing.
if_unmodified_since
datetime – Value of the If-Unmodified-Since header, or None
if the header is missing.
if_range
str – Value of the If-Range header, or None
if the header is missing.
headers
dict – 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. This parsing can be costly, so unless you need all the headers in this format, you should use the get_header
method or one of the convenience attributes instead, to get a value for a specific header.
params
dict – 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.
options
dict – Set of global options passed from the API handler.
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 dict
get_header(name, required=False, default=None)
[source]
Retrieve the raw string value for the given header.
Parameters: |
name (str) – Header name, case-insensitive (e.g., ‘Content-Type’) |
---|---|
Keyword Arguments: | |
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: | |
Raises: |
|
get_header_as_datetime(header, required=False, obs_date=False)
[source]
Return an HTTP header with HTTP-Date values as a datetime.
Parameters: |
name (str) – Header name, case-insensitive (e.g., ‘Date’) |
---|---|
Keyword Arguments: | |
Returns: |
The value of the specified header if it exists, or |
Return type: | |
Raises: |
|
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.
Parameters: |
name (str) – Parameter name, case-sensitive (e.g., ‘sort’). |
---|---|
Keyword Arguments: | |
| |
Returns: |
The value of the param as a string, or |
Return type: | |
Raises: |
|
get_param_as_bool(name, required=False, store=None, blank_as_true=False)
[source]
Return the value of a query string parameter as a boolean
The following boolean strings are supported:
TRUE_STRINGS = ('true', 'True', 'yes', '1', 'on') FALSE_STRINGS = ('false', 'False', 'no', '0', 'off')
Parameters: |
name (str) – Parameter name, case-sensitive (e.g., ‘detailed’). |
---|---|
Keyword Arguments: | |
| |
Returns: |
The value of the param if it is found and can be converted to a |
Return type: | |
Raises: |
|
get_param_as_date(name, format_string='%Y-%m-%d', required=False, store=None)
[source]
Return the value of a query string parameter as a date.
Parameters: |
name (str) – Parameter name, case-sensitive (e.g., ‘ids’). |
---|---|
Keyword Arguments: | |
| |
Returns: |
The value of the param if it is found and can be converted to a |
Return type: | |
Raises: |
|
get_param_as_datetime(name, format_string='%Y-%m-%dT%H:%M:%SZ', required=False, store=None)
[source]
Return the value of a query string parameter as a datetime.
Parameters: |
name (str) – Parameter name, case-sensitive (e.g., ‘ids’). |
---|---|
Keyword Arguments: | |
| |
Returns: |
The value of the param if it is found and can be converted to a |
Return type: | |
Raises: |
|
get_param_as_dict(name, required=False, store=None)
Deprecated alias of get_param_as_json()
.
Warning
This method has been deprecated and will be removed in a future release.
get_param_as_int(name, required=False, min=None, max=None, store=None)
[source]
Return the value of a query string parameter as an int.
Parameters: |
name (str) – Parameter name, case-sensitive (e.g., ‘limit’). |
---|---|
Keyword Arguments: | |
| |
Returns: |
The value of the param if it is found and can be converted to an |
Return type: |
int
. Also raised if the param’s value falls outside the given interval, i.e., the value must be in the interval: min <= value <= max to avoid triggering an error.get_param_as_json(name, required=False, store=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.)
Parameters: |
name (str) – Parameter name, case-sensitive (e.g., ‘payload’). |
---|---|
Keyword Arguments: | |
Returns: |
The value of the param if it is found. Otherwise, returns |
Return type: | |
Raises: |
|
get_param_as_list(name, transform=None, required=False, store=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.
Parameters: |
name (str) – Parameter name, case-sensitive (e.g., ‘ids’). |
---|---|
Keyword Arguments: | |
| |
Returns: |
The value of the param if it is found. Otherwise, returns things=1,,3 things=1&things=&things=3 |
Return type: |
list |
Raises: |
|
get_param_as_uuid(name, required=False, store=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'
Parameters: |
name (str) – Parameter name, case-sensitive (e.g., ‘id’). |
---|---|
Keyword Arguments: | |
Returns: |
The value of the param if it is found and can be converted to a |
Return type: |
UUID |
UUID
.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
str – The value of the “for” parameter, or None
if the parameter is absent. Identifies the node making the request to the proxy.
dest
str – The value of the “by” parameter, or None
if the parameter is absent. Identifies the client-facing interface of the proxy.
host
str – The value of the “host” parameter, or None
if the parameter is absent. Provides the host request header field as received by the proxy.
scheme
str – 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.
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
str – 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
.
media
object – A serializable object supported by the media handlers configured via falcon.RequestOptions
.
See Media for more information regarding media handling.
body
str or unicode – 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).
data
bytes – 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.
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.
stream_len
int – Expected length of stream
. If stream
is set, but stream_len
is not, Falcon will not supply a Content-Length header to the WSGI server. Consequently, the server may choose to use chunked encoding or one of the other strategies suggested by PEP-3333.
context
dict – 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.
context_type
class – Class variable that determines the factory or type to use for initializing the context
attribute. By default, the framework will instantiate standard dict
objects. 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).
options
dict – Set of global options passed from the API handler.
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: |
|
---|---|
Keyword Arguments: | |
|
append_header(name, value)
[source]
Set or append a header for this response.
Warning
If the header already exists, the new value will be appended to it, delimited by a comma. Most header specifications support this format, Set-Cookie being the notable exceptions.
Warning
For setting cookies, see set_cookie()
Parameters: |
|
---|
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_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 dict
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).
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
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. |
---|
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.
get_header(name)
[source]
Retrieve the raw string value for the given header.
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. |
---|---|
Returns: | The header’s value if set, otherwise None . |
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 a response cookie.
Note
This method can be called multiple times to add one or more cookies to the response.
See also
To learn more about setting cookies, see Setting Cookies. The parameters listed below correspond to those defined in RFC 6265.
Parameters: | |
---|---|
Keyword Arguments: | |
| |
Raises: |
|
set_header(name, value)
[source]
Set a header for this response to a given value.
Warning
Calling this method overwrites the existing value, if any.
Warning
For setting cookies, see instead set_cookie()
Parameters: |
|
---|
set_headers(headers)
[source]
Set several headers at once.
Warning
Calling this method overwrites existing values, if any.
Parameters: |
headers (dict or list) – A dictionary of header names and values to set, or a Note Falcon can process a list of tuples slightly faster than a dict. |
---|---|
Raises: |
ValueError – headers was not a dict or list of tuple . |
set_stream(stream, stream_len)
[source]
Convenience method for setting both stream
and stream_len
.
Although the stream
and stream_len
properties may be set directly, using this method ensures stream_len
is not accidentally neglected when the length of the stream is known in advance.
Note
If the stream length is unknown, you can set stream
directly, and ignore stream_len
. In this case, the WSGI server may choose to use chunked encoding or one of the other strategies suggested by PEP-3333.
Unset a cookie in the response
Clears the contents of the cookie, and instructs the user agent to immediately expire its own copy of the cookie.
Warning
In order to successfully remove a cookie, both the path and the domain must match the values that were used when the cookie was created.
vary
Value to use for the Vary header.
Set this property to an iterable of header names. For a single asterisk or field value, simply pass a single-element list
or tuple
.
The “Vary” header field in a response describes what parts of a request message, aside from the method, Host header field, and request target, might influence the origin server’s process for selecting and representing this response. The value consists of either a single asterisk (“*”) or a list of header field names (case-insensitive).
(See also: RFC 7231, Section 7.1.4)
© 2012–2017 by Rackspace Hosting, Inc. and other contributors
Licensed under the Apache License, Version 2.0.
https://falcon.readthedocs.io/en/1.4.1/api/request_and_response.html