Scrapy源码 Response对象

Scrapy源码 Response对象

"""
This module implements the Response class which is used to represent HTTP
responses in Scrapy.

See documentation in docs/topics/request-response.rst
"""
from six.moves.urllib.parse import urljoin

from scrapy.http.request import Request
from scrapy.http.headers import Headers
from scrapy.link import Link
from scrapy.utils.trackref import object_ref
from scrapy.http.common import obsolete_setter
from scrapy.exceptions import NotSupported


class Response(object_ref):

    def __init__(self, url, status=200, headers=None, body=b'', flags=None, request=None):
        self.headers = Headers(headers or {})
        self.status = int(status)
        self._set_body(body)
        self._set_url(url)
        self.request = request
        self.flags = [] if flags is None else list(flags)

    @property
    def meta(self):
        try:
            return self.request.meta
        except AttributeError:
            raise AttributeError(
                "Response.meta not available, this response "
                "is not tied to any request"
            )

    def _get_url(self):
        return self._url

    def _set_url(self, url):
        if isinstance(url, str):
            self._url = url
        else:
            raise TypeError('%s url must be str, got %s:' % (type(self).__name__,
                type(url).__name__))

    url = property(_get_url, obsolete_setter(_set_url, 'url'))

    def _get_body(self):
        return self._body

    def _set_body(self, body):
        if body is None:
            self._body = b''
        elif not isinstance(body, bytes):
            raise TypeError(
                "Response body must be bytes. "
                "If you want to pass unicode body use TextResponse "
                "or HtmlResponse.")
        else:
            self._body = body

    body = property(_get_body, obsolete_setter(_set_body, 'body'))

    def __str__(self):
        return "<%d %s>" % (self.status, self.url)

    __repr__ = __str__

    def copy(self):
        """Return a copy of this Response"""
        return self.replace()

    def replace(self, *args, **kwargs):
        """Create a new Response with the same attributes except for those
        given new values.
        """
        for x in ['url', 'status', 'headers', 'body', 'request', 'flags']:
            kwargs.setdefault(x, getattr(self, x))
        cls = kwargs.pop('cls', self.__class__)
        return cls(*args, **kwargs)

    def urljoin(self, url):
        """Join this Response's url with a possible relative url to form an
        absolute interpretation of the latter."""
        return urljoin(self.url, url)

    @property
    def text(self):
        """For subclasses of TextResponse, this will return the body
        as text (unicode object in Python 2 and str in Python 3)
        """
        raise AttributeError("Response content isn't text")

    def css(self, *a, **kw):
        """Shortcut method implemented only by responses whose content
        is text (subclasses of TextResponse).
        """
        raise NotSupported("Response content isn't text")

    def xpath(self, *a, **kw):
        """Shortcut method implemented only by responses whose content
        is text (subclasses of TextResponse).
        """
        raise NotSupported("Response content isn't text")

    def follow(self, url, callback=None, method='GET', headers=None, body=None,
               cookies=None, meta=None, encoding='utf-8', priority=0,
               dont_filter=False, errback=None, cb_kwargs=None):
        # type: (...) -> Request
        """
        Return a :class:`~.Request` instance to follow a link ``url``.
        It accepts the same arguments as ``Request.__init__`` method,
        but ``url`` can be a relative URL or a ``scrapy.link.Link`` object,
        not only an absolute URL.
        
        :class:`~.TextResponse` provides a :meth:`~.TextResponse.follow` 
        method which supports selectors in addition to absolute/relative URLs
        and Link objects.
        """
        if isinstance(url, Link):
            url = url.url
        elif url is None:
            raise ValueError("url can't be None")
        url = self.urljoin(url)
        return Request(url, callback,
                       method=method,
                       headers=headers,
                       body=body,
                       cookies=cookies,
                       meta=meta,
                       encoding=encoding,
                       priority=priority,
                       dont_filter=dont_filter,
                       errback=errback,
                       cb_kwargs=cb_kwargs)