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.. _topics-request-response:
======================
Requests and Responses
======================
.. module:: scrapy.http
:synopsis: Request and Response classes
Scrapy uses :class:`Request` and :class:`Response` objects for crawling web
sites.
Typically, :class:`Request` objects are generated in the spiders and pass
across the system until they reach the Downloader, which executes the request
and returns a :class:`Response` object which travels back to the spider that
issued the request.
Both :class:`Request` and :class:`Response` classes have subclasses which add
functionality not required in the base classes. These are described
below in :ref:`topics-request-response-ref-request-subclasses` and
:ref:`topics-request-response-ref-response-subclasses`.
Request objects
===============
.. autoclass:: Request
:param url: the URL of this request
If the URL is invalid, a :exc:`ValueError` exception is raised.
:type url: str
:param callback: the function that will be called with the response of this
request (once it's downloaded) as its first parameter.
In addition to a function, the following values are supported:
- ``None`` (default), which indicates that the spider's
:meth:`~scrapy.Spider.parse` method must be used.
- :func:`~scrapy.http.request.NO_CALLBACK`
For more information, see
:ref:`topics-request-response-ref-request-callback-arguments`.
.. note:: If exceptions are raised during processing, ``errback`` is
called instead.
:type callback: collections.abc.Callable
:param method: the HTTP method of this request. Defaults to ``'GET'``.
:type method: str
:param meta: the initial values for the :attr:`Request.meta` attribute. If
given, the dict passed in this parameter will be shallow copied.
:type meta: dict
:param body: the request body. If a string is passed, then it's encoded as
bytes using the ``encoding`` passed (which defaults to ``utf-8``). If
``body`` is not given, an empty bytes object is stored. Regardless of the
type of this argument, the final value stored will be a bytes object
(never a string or ``None``).
:type body: bytes or str
:param headers: the headers of this request. The dict values can be strings
(for single valued headers) or lists (for multi-valued headers). If
``None`` is passed as value, the HTTP header will not be sent at all.
.. caution:: Cookies set via the ``Cookie`` header are not considered by the
:ref:`cookies-mw`. If you need to set cookies for a request, use the
:class:`Request.cookies <scrapy.Request>` parameter. This is a known
current limitation that is being worked on.
:type headers: dict
:param cookies: the request cookies. These can be sent in two forms.
1. Using a dict:
.. code-block:: python
request_with_cookies = Request(
url="http://www.example.com",
cookies={"currency": "USD", "country": "UY"},
)
2. Using a list of dicts:
.. code-block:: python
request_with_cookies = Request(
url="http://www.example.com",
cookies=[
{
"name": "currency",
"value": "USD",
"domain": "example.com",
"path": "/currency",
},
],
)
The latter form allows for customizing the ``domain`` and ``path``
attributes of the cookie. This is only useful if the cookies are saved
for later requests.
.. reqmeta:: dont_merge_cookies
When some site returns cookies (in a response) those are stored in the
cookies for that domain and will be sent again in future requests.
That's the typical behaviour of any regular web browser.
To create a request that does not send stored cookies and does not
store received cookies, set the ``dont_merge_cookies`` key to ``True``
in :attr:`request.meta <scrapy.Request.meta>`.
Example of a request that sends manually-defined cookies and ignores
cookie storage:
.. code-block:: python
Request(
url="http://www.example.com",
cookies={"currency": "USD", "country": "UY"},
meta={"dont_merge_cookies": True},
)
For more info see :ref:`cookies-mw`.
.. caution:: Cookies set via the ``Cookie`` header are not considered by the
:ref:`cookies-mw`. If you need to set cookies for a request, use the
:class:`Request.cookies <scrapy.Request>` parameter. This is a known
current limitation that is being worked on.
.. versionadded:: 2.6.0
Cookie values that are :class:`bool`, :class:`float` or :class:`int`
are casted to :class:`str`.
:type cookies: dict or list
:param encoding: the encoding of this request (defaults to ``'utf-8'``).
This encoding will be used to percent-encode the URL and to convert the
body to bytes (if given as a string).
:type encoding: str
:param priority: the priority of this request (defaults to ``0``).
The priority is used by the scheduler to define the order used to process
requests. Requests with a higher priority value will execute earlier.
Negative values are allowed in order to indicate relatively low-priority.
:type priority: int
:param dont_filter: indicates that this request should not be filtered by
the scheduler. This is used when you want to perform an identical
request multiple times, to ignore the duplicates filter. Use it with
care, or you will get into crawling loops. Default to ``False``.
:type dont_filter: bool
:param errback: a function that will be called if any exception was
raised while processing the request. This includes pages that failed
with 404 HTTP errors and such. It receives a
:exc:`~twisted.python.failure.Failure` as first parameter.
For more information,
see :ref:`topics-request-response-ref-errbacks` below.
.. versionchanged:: 2.0
The *callback* parameter is no longer required when the *errback*
parameter is specified.
:type errback: collections.abc.Callable
:param flags: Flags sent to the request, can be used for logging or similar purposes.
:type flags: list
:param cb_kwargs: A dict with arbitrary data that will be passed as keyword arguments to the Request's callback.
:type cb_kwargs: dict
.. attribute:: Request.url
A string containing the URL of this request. Keep in mind that this
attribute contains the escaped URL, so it can differ from the URL passed in
the ``__init__`` method.
This attribute is read-only. To change the URL of a Request use
:meth:`replace`.
.. attribute:: Request.method
A string representing the HTTP method in the request. This is guaranteed to
be uppercase. Example: ``"GET"``, ``"POST"``, ``"PUT"``, etc
.. attribute:: Request.headers
A dictionary-like object which contains the request headers.
.. attribute:: Request.body
The request body as bytes.
This attribute is read-only. To change the body of a Request use
:meth:`replace`.
.. attribute:: Request.meta
A dict that contains arbitrary metadata for this request. This dict is
empty for new Requests, and is usually populated by different Scrapy
components (extensions, middlewares, etc). So the data contained in this
dict depends on the extensions you have enabled.
See :ref:`topics-request-meta` for a list of special meta keys
recognized by Scrapy.
This dict is :doc:`shallow copied <library/copy>` when the request is
cloned using the ``copy()`` or ``replace()`` methods, and can also be
accessed, in your spider, from the ``response.meta`` attribute.
.. attribute:: Request.cb_kwargs
A dictionary that contains arbitrary metadata for this request. Its contents
will be passed to the Request's callback as keyword arguments. It is empty
for new Requests, which means by default callbacks only get a :class:`Response`
object as argument.
This dict is :doc:`shallow copied <library/copy>` when the request is
cloned using the ``copy()`` or ``replace()`` methods, and can also be
accessed, in your spider, from the ``response.cb_kwargs`` attribute.
In case of a failure to process the request, this dict can be accessed as
``failure.request.cb_kwargs`` in the request's errback. For more information,
see :ref:`errback-cb_kwargs`.
.. autoattribute:: Request.attributes
.. method:: Request.copy()
Return a new Request which is a copy of this Request. See also:
:ref:`topics-request-response-ref-request-callback-arguments`.
.. method:: Request.replace([url, method, headers, body, cookies, meta, flags, encoding, priority, dont_filter, callback, errback, cb_kwargs])
Return a Request object with the same members, except for those members
given new values by whichever keyword arguments are specified. The
:attr:`Request.cb_kwargs` and :attr:`Request.meta` attributes are shallow
copied by default (unless new values are given as arguments). See also
:ref:`topics-request-response-ref-request-callback-arguments`.
.. automethod:: from_curl
.. automethod:: to_dict
Other functions related to requests
-----------------------------------
.. autofunction:: scrapy.http.request.NO_CALLBACK
.. autofunction:: scrapy.utils.request.request_from_dict
.. _topics-request-response-ref-request-callback-arguments:
Passing additional data to callback functions
---------------------------------------------
The callback of a request is a function that will be called when the response
of that request is downloaded. The callback function will be called with the
downloaded :class:`Response` object as its first argument.
Example:
.. code-block:: python
def parse_page1(self, response):
return scrapy.Request(
"http://www.example.com/some_page.html", callback=self.parse_page2
)
def parse_page2(self, response):
# this would log http://www.example.com/some_page.html
self.logger.info("Visited %s", response.url)
In some cases you may be interested in passing arguments to those callback
functions so you can receive the arguments later, in the second callback.
The following example shows how to achieve this by using the
:attr:`Request.cb_kwargs` attribute:
.. code-block:: python
def parse(self, response):
request = scrapy.Request(
"http://www.example.com/index.html",
callback=self.parse_page2,
cb_kwargs=dict(main_url=response.url),
)
request.cb_kwargs["foo"] = "bar" # add more arguments for the callback
yield request
def parse_page2(self, response, main_url, foo):
yield dict(
main_url=main_url,
other_url=response.url,
foo=foo,
)
.. caution:: :attr:`Request.cb_kwargs` was introduced in version ``1.7``.
Prior to that, using :attr:`Request.meta` was recommended for passing
information around callbacks. After ``1.7``, :attr:`Request.cb_kwargs`
became the preferred way for handling user information, leaving :attr:`Request.meta`
for communication with components like middlewares and extensions.
.. _topics-request-response-ref-errbacks:
Using errbacks to catch exceptions in request processing
--------------------------------------------------------
The errback of a request is a function that will be called when an exception
is raise while processing it.
It receives a :exc:`~twisted.python.failure.Failure` as first parameter and can
be used to track connection establishment timeouts, DNS errors etc.
Here's an example spider logging all errors and catching some specific
errors if needed:
.. code-block:: python
import scrapy
from scrapy.spidermiddlewares.httperror import HttpError
from twisted.internet.error import DNSLookupError
from twisted.internet.error import TimeoutError, TCPTimedOutError
class ErrbackSpider(scrapy.Spider):
name = "errback_example"
start_urls = [
"http://www.httpbin.org/", # HTTP 200 expected
"http://www.httpbin.org/status/404", # Not found error
"http://www.httpbin.org/status/500", # server issue
"http://www.httpbin.org:12345/", # non-responding host, timeout expected
"https://example.invalid/", # DNS error expected
]
def start_requests(self):
for u in self.start_urls:
yield scrapy.Request(
u,
callback=self.parse_httpbin,
errback=self.errback_httpbin,
dont_filter=True,
)
def parse_httpbin(self, response):
self.logger.info("Got successful response from {}".format(response.url))
# do something useful here...
def errback_httpbin(self, failure):
# log all failures
self.logger.error(repr(failure))
# in case you want to do something special for some errors,
# you may need the failure's type:
if failure.check(HttpError):
# these exceptions come from HttpError spider middleware
# you can get the non-200 response
response = failure.value.response
self.logger.error("HttpError on %s", response.url)
elif failure.check(DNSLookupError):
# this is the original request
request = failure.request
self.logger.error("DNSLookupError on %s", request.url)
elif failure.check(TimeoutError, TCPTimedOutError):
request = failure.request
self.logger.error("TimeoutError on %s", request.url)
.. _errback-cb_kwargs:
Accessing additional data in errback functions
----------------------------------------------
In case of a failure to process the request, you may be interested in
accessing arguments to the callback functions so you can process further
based on the arguments in the errback. The following example shows how to
achieve this by using ``Failure.request.cb_kwargs``:
.. code-block:: python
def parse(self, response):
request = scrapy.Request(
"http://www.example.com/index.html",
callback=self.parse_page2,
errback=self.errback_page2,
cb_kwargs=dict(main_url=response.url),
)
yield request
def parse_page2(self, response, main_url):
pass
def errback_page2(self, failure):
yield dict(
main_url=failure.request.cb_kwargs["main_url"],
)
.. _request-fingerprints:
Request fingerprints
--------------------
There are some aspects of scraping, such as filtering out duplicate requests
(see :setting:`DUPEFILTER_CLASS`) or caching responses (see
:setting:`HTTPCACHE_POLICY`), where you need the ability to generate a short,
unique identifier from a :class:`~scrapy.http.Request` object: a request
fingerprint.
You often do not need to worry about request fingerprints, the default request
fingerprinter works for most projects.
However, there is no universal way to generate a unique identifier from a
request, because different situations require comparing requests differently.
For example, sometimes you may need to compare URLs case-insensitively, include
URL fragments, exclude certain URL query parameters, include some or all
headers, etc.
To change how request fingerprints are built for your requests, use the
:setting:`REQUEST_FINGERPRINTER_CLASS` setting.
.. setting:: REQUEST_FINGERPRINTER_CLASS
REQUEST_FINGERPRINTER_CLASS
~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. versionadded:: 2.7
Default: :class:`scrapy.utils.request.RequestFingerprinter`
A :ref:`request fingerprinter class <custom-request-fingerprinter>` or its
import path.
.. autoclass:: scrapy.utils.request.RequestFingerprinter
.. setting:: REQUEST_FINGERPRINTER_IMPLEMENTATION
REQUEST_FINGERPRINTER_IMPLEMENTATION
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. versionadded:: 2.7
Default: ``'2.6'``
Determines which request fingerprinting algorithm is used by the default
request fingerprinter class (see :setting:`REQUEST_FINGERPRINTER_CLASS`).
Possible values are:
- ``'2.6'`` (default)
This implementation uses the same request fingerprinting algorithm as
Scrapy 2.6 and earlier versions.
Even though this is the default value for backward compatibility reasons,
it is a deprecated value.
- ``'2.7'``
This implementation was introduced in Scrapy 2.7 to fix an issue of the
previous implementation.
New projects should use this value. The :command:`startproject` command
sets this value in the generated ``settings.py`` file.
If you are using the default value (``'2.6'``) for this setting, and you are
using Scrapy components where changing the request fingerprinting algorithm
would cause undesired results, you need to carefully decide when to change the
value of this setting, or switch the :setting:`REQUEST_FINGERPRINTER_CLASS`
setting to a custom request fingerprinter class that implements the 2.6 request
fingerprinting algorithm and does not log this warning (
:ref:`2.6-request-fingerprinter` includes an example implementation of such a
class).
Scenarios where changing the request fingerprinting algorithm may cause
undesired results include, for example, using the HTTP cache middleware (see
:class:`~scrapy.downloadermiddlewares.httpcache.HttpCacheMiddleware`).
Changing the request fingerprinting algorithm would invalidate the current
cache, requiring you to redownload all requests again.
Otherwise, set :setting:`REQUEST_FINGERPRINTER_IMPLEMENTATION` to ``'2.7'`` in
your settings to switch already to the request fingerprinting implementation
that will be the only request fingerprinting implementation available in a
future version of Scrapy, and remove the deprecation warning triggered by using
the default value (``'2.6'``).
.. _2.6-request-fingerprinter:
.. _custom-request-fingerprinter:
Writing your own request fingerprinter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A request fingerprinter is a class that must implement the following method:
.. currentmodule:: None
.. method:: fingerprint(self, request)
Return a :class:`bytes` object that uniquely identifies *request*.
See also :ref:`request-fingerprint-restrictions`.
:param request: request to fingerprint
:type request: scrapy.http.Request
Additionally, it may also implement the following methods:
.. classmethod:: from_crawler(cls, crawler)
:noindex:
If present, this class method is called to create a request fingerprinter
instance from a :class:`~scrapy.crawler.Crawler` object. It must return a
new instance of the request fingerprinter.
*crawler* provides access to all Scrapy core components like settings and
signals; it is a way for the request fingerprinter to access them and hook
its functionality into Scrapy.
:param crawler: crawler that uses this request fingerprinter
:type crawler: :class:`~scrapy.crawler.Crawler` object
.. classmethod:: from_settings(cls, settings)
If present, and ``from_crawler`` is not defined, this class method is called
to create a request fingerprinter instance from a
:class:`~scrapy.settings.Settings` object. It must return a new instance of
the request fingerprinter.
.. currentmodule:: scrapy.http
The :meth:`fingerprint` method of the default request fingerprinter,
:class:`scrapy.utils.request.RequestFingerprinter`, uses
:func:`scrapy.utils.request.fingerprint` with its default parameters. For some
common use cases you can use :func:`scrapy.utils.request.fingerprint` as well
in your :meth:`fingerprint` method implementation:
.. autofunction:: scrapy.utils.request.fingerprint
For example, to take the value of a request header named ``X-ID`` into
account:
.. code-block:: python
# my_project/settings.py
REQUEST_FINGERPRINTER_CLASS = "my_project.utils.RequestFingerprinter"
# my_project/utils.py
from scrapy.utils.request import fingerprint
class RequestFingerprinter:
def fingerprint(self, request):
return fingerprint(request, include_headers=["X-ID"])
You can also write your own fingerprinting logic from scratch.
However, if you do not use :func:`scrapy.utils.request.fingerprint`, make sure
you use :class:`~weakref.WeakKeyDictionary` to cache request fingerprints:
- Caching saves CPU by ensuring that fingerprints are calculated only once
per request, and not once per Scrapy component that needs the fingerprint
of a request.
- Using :class:`~weakref.WeakKeyDictionary` saves memory by ensuring that
request objects do not stay in memory forever just because you have
references to them in your cache dictionary.
For example, to take into account only the URL of a request, without any prior
URL canonicalization or taking the request method or body into account:
.. code-block:: python
from hashlib import sha1
from weakref import WeakKeyDictionary
from scrapy.utils.python import to_bytes
class RequestFingerprinter:
cache = WeakKeyDictionary()
def fingerprint(self, request):
if request not in self.cache:
fp = sha1()
fp.update(to_bytes(request.url))
self.cache[request] = fp.digest()
return self.cache[request]
If you need to be able to override the request fingerprinting for arbitrary
requests from your spider callbacks, you may implement a request fingerprinter
that reads fingerprints from :attr:`request.meta <scrapy.http.Request.meta>`
when available, and then falls back to
:func:`scrapy.utils.request.fingerprint`. For example:
.. code-block:: python
from scrapy.utils.request import fingerprint
class RequestFingerprinter:
def fingerprint(self, request):
if "fingerprint" in request.meta:
return request.meta["fingerprint"]
return fingerprint(request)
If you need to reproduce the same fingerprinting algorithm as Scrapy 2.6
without using the deprecated ``'2.6'`` value of the
:setting:`REQUEST_FINGERPRINTER_IMPLEMENTATION` setting, use the following
request fingerprinter:
.. code-block:: python
from hashlib import sha1
from weakref import WeakKeyDictionary
from scrapy.utils.python import to_bytes
from w3lib.url import canonicalize_url
class RequestFingerprinter:
cache = WeakKeyDictionary()
def fingerprint(self, request):
if request not in self.cache:
fp = sha1()
fp.update(to_bytes(request.method))
fp.update(to_bytes(canonicalize_url(request.url)))
fp.update(request.body or b"")
self.cache[request] = fp.digest()
return self.cache[request]
.. _request-fingerprint-restrictions:
Request fingerprint restrictions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Scrapy components that use request fingerprints may impose additional
restrictions on the format of the fingerprints that your :ref:`request
fingerprinter <custom-request-fingerprinter>` generates.
The following built-in Scrapy components have such restrictions:
- :class:`scrapy.extensions.httpcache.FilesystemCacheStorage` (default
value of :setting:`HTTPCACHE_STORAGE`)
Request fingerprints must be at least 1 byte long.
Path and filename length limits of the file system of
:setting:`HTTPCACHE_DIR` also apply. Inside :setting:`HTTPCACHE_DIR`,
the following directory structure is created:
- :attr:`Spider.name <scrapy.spiders.Spider.name>`
- first byte of a request fingerprint as hexadecimal
- fingerprint as hexadecimal
- filenames up to 16 characters long
For example, if a request fingerprint is made of 20 bytes (default),
:setting:`HTTPCACHE_DIR` is ``'/home/user/project/.scrapy/httpcache'``,
and the name of your spider is ``'my_spider'`` your file system must
support a file path like::
/home/user/project/.scrapy/httpcache/my_spider/01/0123456789abcdef0123456789abcdef01234567/response_headers
- :class:`scrapy.extensions.httpcache.DbmCacheStorage`
The underlying DBM implementation must support keys as long as twice
the number of bytes of a request fingerprint, plus 5. For example,
if a request fingerprint is made of 20 bytes (default),
45-character-long keys must be supported.
.. _topics-request-meta:
Request.meta special keys
=========================
The :attr:`Request.meta` attribute can contain any arbitrary data, but there
are some special keys recognized by Scrapy and its built-in extensions.
Those are:
* :reqmeta:`bindaddress`
* :reqmeta:`cookiejar`
* :reqmeta:`dont_cache`
* :reqmeta:`dont_merge_cookies`
* :reqmeta:`dont_obey_robotstxt`
* :reqmeta:`dont_redirect`
* :reqmeta:`dont_retry`
* :reqmeta:`download_fail_on_dataloss`
* :reqmeta:`download_latency`
* :reqmeta:`download_maxsize`
* :reqmeta:`download_timeout`
* ``ftp_password`` (See :setting:`FTP_PASSWORD` for more info)
* ``ftp_user`` (See :setting:`FTP_USER` for more info)
* :reqmeta:`handle_httpstatus_all`
* :reqmeta:`handle_httpstatus_list`
* :reqmeta:`max_retry_times`
* :reqmeta:`proxy`
* :reqmeta:`redirect_reasons`
* :reqmeta:`redirect_urls`
* :reqmeta:`referrer_policy`
.. reqmeta:: bindaddress
bindaddress
-----------
The IP of the outgoing IP address to use for the performing the request.
.. reqmeta:: download_timeout
download_timeout
----------------
The amount of time (in secs) that the downloader will wait before timing out.
See also: :setting:`DOWNLOAD_TIMEOUT`.
.. reqmeta:: download_latency
download_latency
----------------
The amount of time spent to fetch the response, since the request has been
started, i.e. HTTP message sent over the network. This meta key only becomes
available when the response has been downloaded. While most other meta keys are
used to control Scrapy behavior, this one is supposed to be read-only.
.. reqmeta:: download_fail_on_dataloss
download_fail_on_dataloss
-------------------------
Whether or not to fail on broken responses. See:
:setting:`DOWNLOAD_FAIL_ON_DATALOSS`.
.. reqmeta:: max_retry_times
max_retry_times
---------------
The meta key is used set retry times per request. When initialized, the
:reqmeta:`max_retry_times` meta key takes higher precedence over the
:setting:`RETRY_TIMES` setting.
.. _topics-stop-response-download:
Stopping the download of a Response
===================================
Raising a :exc:`~scrapy.exceptions.StopDownload` exception from a handler for the
:class:`~scrapy.signals.bytes_received` or :class:`~scrapy.signals.headers_received`
signals will stop the download of a given response. See the following example:
.. code-block:: python
import scrapy
class StopSpider(scrapy.Spider):
name = "stop"
start_urls = ["https://docs.scrapy.org/en/latest/"]
@classmethod
def from_crawler(cls, crawler):
spider = super().from_crawler(crawler)
crawler.signals.connect(
spider.on_bytes_received, signal=scrapy.signals.bytes_received
)
return spider
def parse(self, response):
# 'last_chars' show that the full response was not downloaded
yield {"len": len(response.text), "last_chars": response.text[-40:]}
def on_bytes_received(self, data, request, spider):
raise scrapy.exceptions.StopDownload(fail=False)
which produces the following output::
2020-05-19 17:26:12 [scrapy.core.engine] INFO: Spider opened
2020-05-19 17:26:12 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2020-05-19 17:26:13 [scrapy.core.downloader.handlers.http11] DEBUG: Download stopped for <GET https://docs.scrapy.org/en/latest/> from signal handler StopSpider.on_bytes_received
2020-05-19 17:26:13 [scrapy.core.engine] DEBUG: Crawled (200) <GET https://docs.scrapy.org/en/latest/> (referer: None) ['download_stopped']
2020-05-19 17:26:13 [scrapy.core.scraper] DEBUG: Scraped from <200 https://docs.scrapy.org/en/latest/>
{'len': 279, 'last_chars': 'dth, initial-scale=1.0">\n \n <title>Scr'}
2020-05-19 17:26:13 [scrapy.core.engine] INFO: Closing spider (finished)
By default, resulting responses are handled by their corresponding errbacks. To
call their callback instead, like in this example, pass ``fail=False`` to the
:exc:`~scrapy.exceptions.StopDownload` exception.
.. _topics-request-response-ref-request-subclasses:
Request subclasses
==================
Here is the list of built-in :class:`Request` subclasses. You can also subclass
it to implement your own custom functionality.
FormRequest objects
-------------------
The FormRequest class extends the base :class:`Request` with functionality for
dealing with HTML forms. It uses `lxml.html forms`_ to pre-populate form
fields with form data from :class:`Response` objects.
.. _lxml.html forms: https://lxml.de/lxmlhtml.html#forms
.. class:: scrapy.http.request.form.FormRequest
.. class:: scrapy.http.FormRequest
.. class:: scrapy.FormRequest(url, [formdata, ...])
The :class:`FormRequest` class adds a new keyword parameter to the ``__init__`` method. The
remaining arguments are the same as for the :class:`Request` class and are
not documented here.
:param formdata: is a dictionary (or iterable of (key, value) tuples)
containing HTML Form data which will be url-encoded and assigned to the
body of the request.
:type formdata: dict or collections.abc.Iterable
The :class:`FormRequest` objects support the following class method in
addition to the standard :class:`Request` methods:
.. classmethod:: FormRequest.from_response(response, [formname=None, formid=None, formnumber=0, formdata=None, formxpath=None, formcss=None, clickdata=None, dont_click=False, ...])
Returns a new :class:`FormRequest` object with its form field values
pre-populated with those found in the HTML ``<form>`` element contained
in the given response. For an example see
:ref:`topics-request-response-ref-request-userlogin`.
The policy is to automatically simulate a click, by default, on any form
control that looks clickable, like a ``<input type="submit">``. Even
though this is quite convenient, and often the desired behaviour,
sometimes it can cause problems which could be hard to debug. For
example, when working with forms that are filled and/or submitted using
javascript, the default :meth:`from_response` behaviour may not be the
most appropriate. To disable this behaviour you can set the
``dont_click`` argument to ``True``. Also, if you want to change the
control clicked (instead of disabling it) you can also use the
``clickdata`` argument.
.. caution:: Using this method with select elements which have leading
or trailing whitespace in the option values will not work due to a
`bug in lxml`_, which should be fixed in lxml 3.8 and above.
:param response: the response containing a HTML form which will be used
to pre-populate the form fields
:type response: :class:`Response` object
:param formname: if given, the form with name attribute set to this value will be used.
:type formname: str
:param formid: if given, the form with id attribute set to this value will be used.
:type formid: str
:param formxpath: if given, the first form that matches the xpath will be used.
:type formxpath: str
:param formcss: if given, the first form that matches the css selector will be used.
:type formcss: str
:param formnumber: the number of form to use, when the response contains
multiple forms. The first one (and also the default) is ``0``.
:type formnumber: int
:param formdata: fields to override in the form data. If a field was
already present in the response ``<form>`` element, its value is
overridden by the one passed in this parameter. If a value passed in
this parameter is ``None``, the field will not be included in the
request, even if it was present in the response ``<form>`` element.
:type formdata: dict
:param clickdata: attributes to lookup the control clicked. If it's not
given, the form data will be submitted simulating a click on the
first clickable element. In addition to html attributes, the control
can be identified by its zero-based index relative to other
submittable inputs inside the form, via the ``nr`` attribute.
:type clickdata: dict
:param dont_click: If True, the form data will be submitted without
clicking in any element.
:type dont_click: bool
The other parameters of this class method are passed directly to the
:class:`FormRequest` ``__init__`` method.
Request usage examples
----------------------
Using FormRequest to send data via HTTP POST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If you want to simulate a HTML Form POST in your spider and send a couple of
key-value fields, you can return a :class:`FormRequest` object (from your
spider) like this:
.. code-block:: python
return [
FormRequest(
url="http://www.example.com/post/action",
formdata={"name": "John Doe", "age": "27"},
callback=self.after_post,
)
]
.. _topics-request-response-ref-request-userlogin:
Using FormRequest.from_response() to simulate a user login
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is usual for web sites to provide pre-populated form fields through ``<input
type="hidden">`` elements, such as session related data or authentication
tokens (for login pages). When scraping, you'll want these fields to be
automatically pre-populated and only override a couple of them, such as the
user name and password. You can use the :meth:`FormRequest.from_response`
method for this job. Here's an example spider which uses it:
.. code-block:: python
import scrapy
def authentication_failed(response):
# TODO: Check the contents of the response and return True if it failed
# or False if it succeeded.
pass
class LoginSpider(scrapy.Spider):
name = "example.com"
start_urls = ["http://www.example.com/users/login.php"]
def parse(self, response):
return scrapy.FormRequest.from_response(
response,
formdata={"username": "john", "password": "secret"},
callback=self.after_login,
)
def after_login(self, response):
if authentication_failed(response):
self.logger.error("Login failed")
return
# continue scraping with authenticated session...
JsonRequest
-----------
The JsonRequest class extends the base :class:`Request` class with functionality for
dealing with JSON requests.
.. class:: JsonRequest(url, [... data, dumps_kwargs])
The :class:`JsonRequest` class adds two new keyword parameters to the ``__init__`` method. The
remaining arguments are the same as for the :class:`Request` class and are
not documented here.
Using the :class:`JsonRequest` will set the ``Content-Type`` header to ``application/json``
and ``Accept`` header to ``application/json, text/javascript, */*; q=0.01``
:param data: is any JSON serializable object that needs to be JSON encoded and assigned to body.
if :attr:`Request.body` argument is provided this parameter will be ignored.
if :attr:`Request.body` argument is not provided and data argument is provided :attr:`Request.method` will be
set to ``'POST'`` automatically.
:type data: object
:param dumps_kwargs: Parameters that will be passed to underlying :func:`json.dumps` method which is used to serialize
data into JSON format.
:type dumps_kwargs: dict
.. autoattribute:: JsonRequest.attributes
JsonRequest usage example
-------------------------
Sending a JSON POST request with a JSON payload:
.. code-block:: python
data = {
"name1": "value1",
"name2": "value2",
}
yield JsonRequest(url="http://www.example.com/post/action", data=data)
Response objects
================
.. autoclass:: Response
:param url: the URL of this response
:type url: str
:param status: the HTTP status of the response. Defaults to ``200``.
:type status: int
:param headers: the headers of this response. The dict values can be strings
(for single valued headers) or lists (for multi-valued headers).
:type headers: dict
:param body: the response body. To access the decoded text as a string, use
``response.text`` from an encoding-aware
:ref:`Response subclass <topics-request-response-ref-response-subclasses>`,
such as :class:`TextResponse`.
:type body: bytes
:param flags: is a list containing the initial values for the
:attr:`Response.flags` attribute. If given, the list will be shallow
copied.
:type flags: list
:param request: the initial value of the :attr:`Response.request` attribute.
This represents the :class:`Request` that generated this response.
:type request: scrapy.Request
:param certificate: an object representing the server's SSL certificate.
:type certificate: twisted.internet.ssl.Certificate
:param ip_address: The IP address of the server from which the Response originated.
:type ip_address: :class:`ipaddress.IPv4Address` or :class:`ipaddress.IPv6Address`
:param protocol: The protocol that was used to download the response.
For instance: "HTTP/1.0", "HTTP/1.1", "h2"
:type protocol: :class:`str`
.. versionadded:: 2.0.0
The ``certificate`` parameter.
.. versionadded:: 2.1.0
The ``ip_address`` parameter.
.. versionadded:: 2.5.0
The ``protocol`` parameter.
.. attribute:: Response.url
A string containing the URL of the response.
This attribute is read-only. To change the URL of a Response use
:meth:`replace`.
.. attribute:: Response.status
An integer representing the HTTP status of the response. Example: ``200``,
``404``.
.. attribute:: Response.headers
A dictionary-like object which contains the response headers. Values can
be accessed using :meth:`get` to return the first header value with the
specified name or :meth:`getlist` to return all header values with the
specified name. For example, this call will give you all cookies in the
headers::
response.headers.getlist('Set-Cookie')
.. attribute:: Response.body
The response body as bytes.
If you want the body as a string, use :attr:`TextResponse.text` (only
available in :class:`TextResponse` and subclasses).
This attribute is read-only. To change the body of a Response use
:meth:`replace`.
.. attribute:: Response.request
The :class:`Request` object that generated this response. This attribute is
assigned in the Scrapy engine, after the response and the request have passed
through all :ref:`Downloader Middlewares <topics-downloader-middleware>`.
In particular, this means that:
- HTTP redirections will cause the original request (to the URL before
redirection) to be assigned to the redirected response (with the final
URL after redirection).
- Response.request.url doesn't always equal Response.url
- This attribute is only available in the spider code, and in the
:ref:`Spider Middlewares <topics-spider-middleware>`, but not in
Downloader Middlewares (although you have the Request available there by
other means) and handlers of the :signal:`response_downloaded` signal.
.. attribute:: Response.meta
A shortcut to the :attr:`Request.meta` attribute of the
:attr:`Response.request` object (i.e. ``self.request.meta``).
Unlike the :attr:`Response.request` attribute, the :attr:`Response.meta`
attribute is propagated along redirects and retries, so you will get
the original :attr:`Request.meta` sent from your spider.
.. seealso:: :attr:`Request.meta` attribute
.. attribute:: Response.cb_kwargs
.. versionadded:: 2.0
A shortcut to the :attr:`Request.cb_kwargs` attribute of the
:attr:`Response.request` object (i.e. ``self.request.cb_kwargs``).
Unlike the :attr:`Response.request` attribute, the
:attr:`Response.cb_kwargs` attribute is propagated along redirects and
retries, so you will get the original :attr:`Request.cb_kwargs` sent
from your spider.
.. seealso:: :attr:`Request.cb_kwargs` attribute
.. attribute:: Response.flags
A list that contains flags for this response. Flags are labels used for
tagging Responses. For example: ``'cached'``, ``'redirected``', etc. And
they're shown on the string representation of the Response (`__str__`
method) which is used by the engine for logging.
.. attribute:: Response.certificate
.. versionadded:: 2.0.0
A :class:`twisted.internet.ssl.Certificate` object representing
the server's SSL certificate.
Only populated for ``https`` responses, ``None`` otherwise.
.. attribute:: Response.ip_address
.. versionadded:: 2.1.0
The IP address of the server from which the Response originated.
This attribute is currently only populated by the HTTP 1.1 download
handler, i.e. for ``http(s)`` responses. For other handlers,
:attr:`ip_address` is always ``None``.
.. attribute:: Response.protocol
.. versionadded:: 2.5.0
The protocol that was used to download the response.
For instance: "HTTP/1.0", "HTTP/1.1"
This attribute is currently only populated by the HTTP download
handlers, i.e. for ``http(s)`` responses. For other handlers,
:attr:`protocol` is always ``None``.
.. autoattribute:: Response.attributes
.. method:: Response.copy()
Returns a new Response which is a copy of this Response.
.. method:: Response.replace([url, status, headers, body, request, flags, cls])
Returns a Response object with the same members, except for those members
given new values by whichever keyword arguments are specified. The
attribute :attr:`Response.meta` is copied by default.
.. method:: Response.urljoin(url)
Constructs an absolute url by combining the Response's :attr:`url` with
a possible relative url.
This is a wrapper over :func:`~urllib.parse.urljoin`, it's merely an alias for
making this call::
urllib.parse.urljoin(response.url, url)
.. automethod:: Response.follow
.. automethod:: Response.follow_all
.. _topics-request-response-ref-response-subclasses:
Response subclasses
===================
Here is the list of available built-in Response subclasses. You can also
subclass the Response class to implement your own functionality.
TextResponse objects
--------------------
.. class:: TextResponse(url, [encoding[, ...]])
:class:`TextResponse` objects adds encoding capabilities to the base
:class:`Response` class, which is meant to be used only for binary data,
such as images, sounds or any media file.
:class:`TextResponse` objects support a new ``__init__`` method argument, in
addition to the base :class:`Response` objects. The remaining functionality
is the same as for the :class:`Response` class and is not documented here.
:param encoding: is a string which contains the encoding to use for this
response. If you create a :class:`TextResponse` object with a string as
body, it will be converted to bytes encoded using this encoding. If
*encoding* is ``None`` (default), the encoding will be looked up in the
response headers and body instead.
:type encoding: str
:class:`TextResponse` objects support the following attributes in addition
to the standard :class:`Response` ones:
.. attribute:: TextResponse.text
Response body, as a string.
The same as ``response.body.decode(response.encoding)``, but the
result is cached after the first call, so you can access
``response.text`` multiple times without extra overhead.
.. note::
``str(response.body)`` is not a correct way to convert the response
body into a string:
.. code-block:: pycon
>>> str(b"body")
"b'body'"
.. attribute:: TextResponse.encoding
A string with the encoding of this response. The encoding is resolved by
trying the following mechanisms, in order:
1. the encoding passed in the ``__init__`` method ``encoding`` argument
2. the encoding declared in the Content-Type HTTP header. If this
encoding is not valid (i.e. unknown), it is ignored and the next
resolution mechanism is tried.
3. the encoding declared in the response body. The TextResponse class
doesn't provide any special functionality for this. However, the
:class:`HtmlResponse` and :class:`XmlResponse` classes do.
4. the encoding inferred by looking at the response body. This is the more
fragile method but also the last one tried.
.. attribute:: TextResponse.selector
A :class:`~scrapy.Selector` instance using the response as
target. The selector is lazily instantiated on first access.
.. autoattribute:: TextResponse.attributes
:class:`TextResponse` objects support the following methods in addition to
the standard :class:`Response` ones:
.. method:: TextResponse.xpath(query)
A shortcut to ``TextResponse.selector.xpath(query)``::
response.xpath('//p')
.. method:: TextResponse.css(query)
A shortcut to ``TextResponse.selector.css(query)``::
response.css('p')
.. automethod:: TextResponse.follow
.. automethod:: TextResponse.follow_all
.. automethod:: TextResponse.json()
Returns a Python object from deserialized JSON document.
The result is cached after the first call.
.. method:: TextResponse.urljoin(url)
Constructs an absolute url by combining the Response's base url with
a possible relative url. The base url shall be extracted from the
``<base>`` tag, or just the Response's :attr:`url` if there is no such
tag.
HtmlResponse objects
--------------------
.. class:: HtmlResponse(url[, ...])
The :class:`HtmlResponse` class is a subclass of :class:`TextResponse`
which adds encoding auto-discovering support by looking into the HTML `meta
http-equiv`_ attribute. See :attr:`TextResponse.encoding`.
.. _meta http-equiv: https://www.w3schools.com/TAGS/att_meta_http_equiv.asp
XmlResponse objects
-------------------
.. class:: XmlResponse(url[, ...])
The :class:`XmlResponse` class is a subclass of :class:`TextResponse` which
adds encoding auto-discovering support by looking into the XML declaration
line. See :attr:`TextResponse.encoding`.
.. _bug in lxml: https://bugs.launchpad.net/lxml/+bug/1665241
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