scrapy.http
Scrapy uses Request
and Response
objects for crawling web sites.
Typically, Request
objects are generated in the spiders and pass across the system until they reach the Downloader, which executes the request and returns a Response
object which travels back to the spider that issued the request.
Both Request
and Response
classes have subclasses which add functionality not required in the base classes. These are described below in topics-request-response-ref-request-subclasses
and topics-request-response-ref-response-subclasses
.
A Request
object represents an HTTP request, which is usually generated in the Spider and executed by the Downloader, and thus generating a Response
.
- param url
the URL of this request
- type url
string
- param callback
the function that will be called with the response of this request (once its downloaded) as its first parameter. For more information see
topics-request-response-ref-request-callback-arguments
below. If a Request doesn't specify a callback, the spider's~scrapy.spider.Spider.parse
method will be used. Note that if exceptions are raised during processing, errback is called instead.- type callback
callable
- param method
the HTTP method of this request. Defaults to
'GET'
.- type method
string
- param meta
the initial values for the
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
unicode
is passed, then it's encoded tostr
using the encoding passed (which defaults toutf-8
). Ifbody
is not given,, an empty string is stored. Regardless of the type of this argument, the final value stored will be astr
(neverunicode
orNone
).- type body
str or unicode
- 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.- type headers
dict
- param cookies
the request cookies. These can be sent in two forms.
Using a dict:
request_with_cookies = Request(url="http://www.example.com", cookies={'currency': 'USD', 'country': 'UY'})
Using a list of dicts:
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
andpath
attributes of the cookie. This is only useful if the cookies are saved for later requests.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. However, if, for some reason, you want to avoid merging with existing cookies you can instruct Scrapy to do so by setting the
dont_merge_cookies
key in theRequest.meta
.Example of request without merging cookies:
request_with_cookies = Request(url="http://www.example.com", cookies={'currency': 'USD', 'country': 'UY'}, meta={'dont_merge_cookies': True})
For more info see
cookies-mw
.
- 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 tostr
(if given asunicode
).- type encoding
string
- 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
boolean
- 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 Twisted Failure instance as first parameter.
- type errback
callable
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 constructor.
This attribute is read-only. To change the URL of a Request use replace
.
Request.method
A string representing the HTTP method in the request. This is guaranteed to be uppercase. Example: "GET"
, "POST"
, "PUT"
, etc
Request.headers
A dictionary-like object which contains the request headers.
Request.body
A str that contains the request body.
This attribute is read-only. To change the body of a Request use replace
.
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 topics-request-meta
for a list of special meta keys recognized by Scrapy.
This dict is shallow copied when the request is cloned using the copy()
or replace()
methods, and can also be accessed, in your spider, from the response.meta
attribute.
Request.copy()
Return a new Request which is a copy of this Request. See also: topics-request-response-ref-request-callback-arguments
.
Request.replace([url, method, headers, body, cookies, meta, encoding, dont_filter, callback, errback])
Return a Request object with the same members, except for those members given new values by whichever keyword arguments are specified. The attribute Request.meta
is copied by default (unless a new value is given in the meta
argument). See also topics-request-response-ref-request-callback-arguments
.
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 Response
object as its first argument.
Example:
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.log("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. You can use the Request.meta
attribute for that.
Here's an example of how to pass an item using this mechanism, to populate different fields from different pages:
def parse_page1(self, response):
item = MyItem()
item['main_url'] = response.url
request = scrapy.Request("http://www.example.com/some_page.html",
callback=self.parse_page2)
request.meta['item'] = item
return request
def parse_page2(self, response):
item = response.meta['item']
item['other_url'] = response.url
return item
The Request.meta
attribute can contain any arbitrary data, but there are some special keys recognized by Scrapy and its built-in extensions.
Those are:
dont_redirect
dont_retry
handle_httpstatus_list
dont_merge_cookies
(seecookies
parameter ofRequest
constructor)cookiejar
redirect_urls
bindaddress
bindaddress
The IP of the outgoing IP address to use for the performing the request.
Here is the list of built-in Request
subclasses. You can also subclass it to implement your own custom functionality.
The FormRequest class extends the base Request
with functionality for dealing with HTML forms. It uses lxml.html forms to pre-populate form fields with form data from Response
objects.
The FormRequest
class adds a new argument to the constructor. The remaining arguments are the same as for the 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 iterable of tuples
The FormRequest
objects support the following class method in addition to the standard Request
methods:
FormRequest.from_response(response, [formname=None, formnumber=0, formdata=None, formxpath=None, clickdata=None, dont_click=False, ...])
Returns a new 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 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 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.
- param response
the response containing a HTML form which will be used to pre-populate the form fields
- type response
Response
object- param formname
if given, the form with name attribute set to this value will be used.
- type formname
string
- param formxpath
if given, the first form that matches the xpath will be used.
- type formxpath
string
- 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
integer
- 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.- 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
boolean
The other parameters of this class method are passed directly to the FormRequest
constructor.
0.10.3 The formname
parameter.
0.17 The formxpath
parameter.
If you want to simulate a HTML Form POST in your spider and send a couple of key-value fields, you can return a FormRequest
object (from your spider) like this:
return [FormRequest(url="http://www.example.com/post/action",
formdata={'name': 'John Doe', 'age': '27'},
callback=self.after_post)]
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 FormRequest.from_response
method for this job. Here's an example spider which uses it:
import scrapy
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):
# check login succeed before going on
if "authentication failed" in response.body:
self.log("Login failed", level=scrapy.log.ERROR)
return
# continue scraping with authenticated session...
A Response
object represents an HTTP response, which is usually downloaded (by the Downloader) and fed to the Spiders for processing.
- param url
the URL of this response
- type url
string
- 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 status
the HTTP status of the response. Defaults to
200
.- type status
integer
- param body
the response body. It must be str, not unicode, unless you're using a encoding-aware
Response subclass <topics-request-response-ref-response-subclasses>
, such asTextResponse
.- type body
str
- param meta
the initial values for the
Response.meta
attribute. If given, the dict will be shallow copied.- type meta
dict
- param flags
is a list containing the initial values for the
Response.flags
attribute. If given, the list will be shallow copied.- type flags
list
Response.url
A string containing the URL of the response.
This attribute is read-only. To change the URL of a Response use replace
.
Response.status
An integer representing the HTTP status of the response. Example: 200
, 404
.
Response.headers
A dictionary-like object which contains the response headers.
Response.body
A str containing the body of this Response. Keep in mind that Response.body is always a str. If you want the unicode version use TextResponse.body_as_unicode
(only available in TextResponse
and subclasses).
This attribute is read-only. To change the body of a Response use replace
.
Response.request
The Request
object that generated this response. This attribute is assigned in the Scrapy engine, after the response and the request have passed through all 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
Spider Middlewares <topics-spider-middleware>
, but not in Downloader Middlewares (although you have the Request available there by other means) and handlers of theresponse_downloaded
signal.
Response.meta
A shortcut to the Request.meta
attribute of the Response.request
object (ie. self.request.meta
).
Unlike the Response.request
attribute, the Response.meta
attribute is propagated along redirects and retries, so you will get the original Request.meta
sent from your spider.
Request.meta
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.
Response.copy()
Returns a new Response which is a copy of this Response.
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 Response.meta
is copied by default.
Here is the list of available built-in Response subclasses. You can also subclass the Response class to implement your own functionality.
TextResponse
objects adds encoding capabilities to the base Response
class, which is meant to be used only for binary data, such as images, sounds or any media file.
TextResponse
objects support a new constructor argument, in addition to the base Response
objects. The remaining functionality is the same as for the 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
TextResponse
object with a unicode body, it will be encoded using this encoding (remember the body attribute is always a string). Ifencoding
isNone
(default value), the encoding will be looked up in the response headers and body instead.- type encoding
string
TextResponse
objects support the following attributes in addition to the standard Response
ones:
TextResponse.encoding
A string with the encoding of this response. The encoding is resolved by trying the following mechanisms, in order:
- the encoding passed in the constructor encoding argument
- the encoding declared in the Content-Type HTTP header. If this encoding is not valid (ie. unknown), it is ignored and the next resolution mechanism is tried.
- the encoding declared in the response body. The TextResponse class doesn't provide any special functionality for this. However, the
HtmlResponse
andXmlResponse
classes do. - the encoding inferred by looking at the response body. This is the more fragile method but also the last one tried.
TextResponse.selector
A ~scrapy.selector.Selector
instance using the response as target. The selector is lazily instantiated on first access.
TextResponse
objects support the following methods in addition to the standard Response
ones:
TextResponse.body_as_unicode()
Returns the body of the response as unicode. This is equivalent to:
response.body.decode(response.encoding)
But not equivalent to:
unicode(response.body)
Since, in the latter case, you would be using the system default encoding (typically ascii) to convert the body to unicode, instead of the response encoding.
TextResponse.xpath(query)
A shortcut to TextResponse.selector.xpath(query)
:
response.xpath('//p')
TextResponse.css(query)
A shortcut to TextResponse.selector.css(query)
:
response.css('p')
The HtmlResponse
class is a subclass of TextResponse
which adds encoding auto-discovering support by looking into the HTML meta http-equiv attribute. See TextResponse.encoding
.
The XmlResponse
class is a subclass of TextResponse
which adds encoding auto-discovering support by looking into the XML declaration line. See TextResponse.encoding
.