我正在尝试制作一个webcrawler,它会转到一个链接并等待Javascript内容加载。然后在进入下一页之前,它应该获得所列文章的所有链接。问题是它总是从第一个url(“https://techcrunch.com/search/heartbleed”)抓取,而不是跟随我给它的。为什么下面的代码没有从我在请求中传递的新url中刮取?我没主意了。。。在
import scrapy
from scrapy.http.request import Request
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support import expected_conditions as EC
from selenium.common.exceptions import TimeoutException
from selenium.webdriver.support.ui import WebDriverWait
import time
class TechcrunchSpider(scrapy.Spider):
name = "techcrunch_spider_performance"
allowed_domains = ['techcrunch.com']
start_urls = ['https://techcrunch.com/search/heartbleed']
def __init__(self):
self.driver = webdriver.PhantomJS()
self.driver.set_window_size(1120, 550)
#self.driver = webdriver.Chrome("C:\Users\Daniel\Desktop\Sonstiges\chromedriver.exe")
self.driver.wait = WebDriverWait(self.driver, 5) #wartet bis zu 5 sekunden
def parse(self, response):
start = time.time() #ZEITMESSUNG
self.driver.get(response.url)
#wartet bis zu 5 sekunden(oben definiert) auf den eintritt der condition, danach schmeist er den TimeoutException error
try:
self.driver.wait.until(EC.presence_of_element_located(
(By.CLASS_NAME, "block-content")))
print("Found : block-content")
except TimeoutException:
self.driver.close()
print(" block-content NOT FOUND IN TECHCRUNCH !!!")
#Crawle durch Javascript erstellte Inhalte mit Selenium
ahref = self.driver.find_elements(By.XPATH,'//h2[@class="post-title st-result-title"]/a')
hreflist = []
#Alle Links zu den jeweiligen Artikeln sammeln
for elem in ahref :
hreflist.append(elem.get_attribute("href"))
for elem in hreflist :
print(elem)
yield scrapy.Request(url=elem , callback=self.parse_content)
#Den link fuer die naechste seite holen
try:
next = self.driver.find_element(By.XPATH,"//a[@class='page-link next']")
nextpage = next.get_attribute("href")
print("JETZT KOMMT NEXT :")
print(nextpage)
#newresponse = response.replace(url=nextpage)
yield scrapy.Request(url=nextpage, dont_filter=False)
except TimeoutException:
self.driver.close()
print(" NEXT NOT FOUND(OR EOF) IM CLOSING MYSELF !!!")
end = time.time()
print("Time elapsed : ")
finaltime = end-start
print(finaltime)
def parse_content(self, response):
title = self.driver.find_element(By.XPATH,"//h1")
titletext = title.get_attribute("innerHTML")
print(" h1 : ")
print(title)
print(titletext)
第一个问题是:
这段代码会对找到的所有链接产生垃圾请求。但是:
^{pr2}$parse_content函数尝试使用驱动程序解析页面。您可以尝试使用scray中的response元素进行解析,或者使用webdriver加载页面(self.driver.get(……)
此外,scrapy是异步的,selenium不是这样的。scrapy不是在scrapy yield请求之后阻塞代码,而是继续执行代码,因为它构建在twisted之上,可以启动多个并发请求。selenium驱动程序实例将无法跟踪来自scrapy的多个并发请求。(一种方法是用selenium代码替换每个产量,即使这意味着要损失执行时间)
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