python - Scrapy with Selenium 爬行但不抓取

Question

我已经阅读了所有关于将 scrapy 用于 AJAX 页面并安装了 selenium webdrive 以简化任务的线程，我的蜘蛛可以部分爬行但无法将任何数据获取到我的项目中。

我的目标是:

1. 从 this page 抓取至 this page

2. 抓取每个项目(帖子)的:

   author_name (xpath:/html/body/div[8]/div/div[1]/div[3]/div[3]/ul/li[2]/div[2]/span[2]/ul/li[3]/a/text())
   author_page_url (xpath:/html/body/div[8]/div/div[1]/div[3]/div[3]/ul/li[2]/div[2]/span[2]/ul/li[3]/a/@href)
   post_title (xpath://a[@class="title_txt"])
   post_page_url (xpath://a[@class="title_txt"]/@href)
   post_text (xpath on a separate post page: //div[@id="a_NMContent/text()")
   

这是我的猴子代码(因为我只是作为一名有抱负的自然语言处理学生在 Python 中迈出第一步，过去主修语言学):

import scrapy
import time
from selenium import webdriver
from scrapy.contrib.linkextractors.lxmlhtml import LxmlLinkExtractor
from scrapy.contrib.spiders import CrawlSpider, Rule
from scrapy.selector import XPathSelector

class ItalkiSpider(CrawlSpider):
    name = "italki"
    allowed_domains = ['italki.com']
    start_urls = ['http://www.italki.com/entries/korean']
    # not sure if the rule is set correctly
    rules = (Rule(LxmlLinkExtractor(allow="\entry"), callback = "parse_post", follow = True),)
    def __init__(self):
        self.driver = webdriver.Firefox()

    def parse(self, response):
        # adding necessary search parameters to the URL
        self.driver.get(response.url+"#language=korean&author-language=russian&marks-min=-5&sort=1&page=1")
        # pressing the "Show More" button at the bottom of the search results page to show the next 15 posts, when all results are loaded to the page, the button disappears
        more_btn = self.driver.find_element_by_xpath('//a[@id="a_show_more"]')

        while more_btn:
            more_btn.click()
            # sometimes waiting for 5 sec made spider close prematurely so keeping it long in case the server is slow
            time.sleep(10)

        # here is where the problem begins, I am making a list of links to all the posts on the big page, but I am afraid links will contain only the first link, because selenium doesn't do the multiple selection as one would expect from this xpath...how can I grab all the links and put them in the links list (and should I?)
        links=self.driver.find_elements_by_xpath('/html/body/div[8]/div/div[1]/div[3]/div[3]/ul/li/div[2]/a')
        for link in links:
            link.click()
            time.sleep(3)

    # this is the function for parsing individual posts, called back by the *parse* method as specified in the rule of the spider; if it is correct, it should have saved at least one post into an item... I don't really understand how and where this callback function gets the response from the new page (the page of the post in this case)...is it automatically loaded to drive and then passed on to the callback function as soon as selenium has clicked on the link (link.click())? or is it all total nonsense...
    def parse_post(self, response):
        hxs = Selector(response)
        item = ItalkiItem()
        item["post_item"] = hxs.xpath('//div [@id="a_NMContent"]/text()').extract()
        return item

Answer 1

让我们换个角度思考:

• 在浏览器中打开页面并单击“显示更多”，直到到达所需页面
• 初始化一个scrapy TextResponse使用当前页面源(加载所有必要的帖子)
• 为每个帖子初始化一个Item，产生一个Request到帖子页面，并将一个item实例从请求传递到响应meta词典

我要介绍的注意事项和更改:

• 使用normal Spider class
• 使用Selenium Waits等待“显示更多”按钮可见
• 关闭 spider_closed signal 中的驱动程序实例调度员

代码:

import scrapy
from scrapy import signals
from scrapy.http import TextResponse 
from scrapy.xlib.pydispatch import dispatcher

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.wait import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC


class ItalkiItem(scrapy.Item):
    title = scrapy.Field()
    url = scrapy.Field()
    text = scrapy.Field()


class ItalkiSpider(scrapy.Spider):
    name = "italki"
    allowed_domains = ['italki.com']
    start_urls = ['http://www.italki.com/entries/korean']

    def __init__(self):
        self.driver = webdriver.Firefox()
        dispatcher.connect(self.spider_closed, signals.spider_closed)

    def spider_closed(self, spider):
        self.driver.close()

    def parse(self, response):
        # selenium part of the job
        self.driver.get('http://www.italki.com/entries/korean')
        while True:
            more_btn = WebDriverWait(self.driver, 10).until(
                EC.visibility_of_element_located((By.ID, "a_show_more"))
            )

            more_btn.click()

            # stop when we reach the desired page
            if self.driver.current_url.endswith('page=52'):
                break

        # now scrapy should do the job
        response = TextResponse(url=response.url, body=self.driver.page_source, encoding='utf-8')
        for post in response.xpath('//ul[@id="content"]/li'):
            item = ItalkiItem()
            item['title'] = post.xpath('.//a[@class="title_txt"]/text()').extract()[0]
            item['url'] = post.xpath('.//a[@class="title_txt"]/@href').extract()[0]

            yield scrapy.Request(item['url'], meta={'item': item}, callback=self.parse_post)

    def parse_post(self, response):
        item = response.meta['item']
        item["text"] = response.xpath('//div[@id="a_NMContent"]/text()').extract()
        return item

这是您应该用作基本代码并改进以填写所有其他字段的内容，例如 author 或 author_url。希望对您有所帮助。