全球热议:Scrapy爬虫Response子类在应用中的问题解析
2023-05-17 12:20:50
目录
正文输入scrapy crawl girl得到如下错误：查看Response类的定义响应子类正文
今天用scrapy爬取壁纸的时候（url：http://pic.netbian.com/4kmein...）絮叨了一些问题，记录下来，供后世探讨，以史为鉴。**
(资料图片)
因为网站是动态渲染的，所以选择scrapy对接selenium（scrapy抓取网页的方式和requests库相似，都是直接模拟HTTP请求，而Scrapy也不能抓取JavaScript动态渲染的网页。）
所以在Downloader Middlewares中需要得到Request并且返回一个Response，问题出在Response，通过查看官方文档发现class scrapy.http.Response(url[, status=200, headers=None, body=b"", flags=None, request=None])，随即通过from scrapy.http import Response导入Response
输入scrapy crawl girl得到如下错误：
*results=response.xpath("//[@id="main"]/div[3]/ul/lia/img")
raise NotSupported("Response content isn"t text")
scrapy.exceptions.NotSupported: Response content isn"t text**
检查相关代码：
# middlewares.py
from scrapy import signals
from scrapy.http import Response
from scrapy.exceptions import IgnoreRequest
import selenium
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
class Pic4KgirlDownloaderMiddleware(object):
# Not all methods need to be defined. If a method is not defined,
# scrapy acts as if the downloader middleware does not modify the
# passed objects.
def process_request(self, request, spider):
# Called for each request that goes through the downloader
# middleware.
# Must either:
# - return None: continue processing this request
# - or return a Response object
# - or return a Request object
# - or raise IgnoreRequest: process_exception() methods of
# installed downloader middleware will be called
try:
self.browser=selenium.webdriver.Chrome()
self.wait=WebDriverWait(self.browser,10)
self.browser.get(request.url)
self.wait.until(EC.presence_of_element_located((By.CSS_SELECTOR, "#main > div.page > a:nth-child(10)")))
return Response(url=request.url,status=200,request=request,body=self.browser.page_source.encode("utf-8"))
#except:
#raise IgnoreRequest()
finally:
self.browser.close()推断问题出在：
return Response(url=request.url,status=200,request=request,body=self.browser.page_source.encode("utf-8"))
查看Response类的定义
@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")说明Response类不可以被直接使用，需要被继承重写方法后才能使用
响应子类
**TextResponse对象** class scrapy.http.TextResponse(url[, encoding[, ...]]) **HtmlResponse对象** class scrapy.http.HtmlResponse(url[, ...]) **XmlResponse对象** class scrapy.http.XmlResponse（url [，... ] ）
举例观察TextResponse的定义from scrapy.http import TextResponse
导入TextResponse发现
class TextResponse(Response):
_DEFAULT_ENCODING = "ascii"
def __init__(self, *args, **kwargs):
self._encoding = kwargs.pop("encoding", None)
self._cached_benc = None
self._cached_ubody = None
self._cached_selector = None
super(TextResponse, self).__init__(*args, **kwargs)其中xpath方法已经被重写
@property
def selector(self):
from scrapy.selector import Selector
if self._cached_selector is None:
self._cached_selector = Selector(self)
return self._cached_selector
def xpath(self, query, **kwargs):
return self.selector.xpath(query, **kwargs)
def css(self, query):
return self.selector.css(query)所以用户想要调用Response类，必须选择调用其子类,并且重写部分方法
Scrapy爬虫入门教程十一 Request和Response（请求和响应）
scrapy文档：https://doc.scrapy.org/en/lat...
中文翻译文档：https://www.jb51.net/article/248161.htm
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