无效的回调请求

Question

我正在尝试抓取这个网站。我正在使用Scrapy的Request，但它不起作用，代码显示出异常行为。以下是我的代码：

        # -*- coding: utf-8 -*-
        from scrapy.spiders import BaseSpider
        from scrapy.selector import Selector
        from scrapy.http import Request,Response
        import re
        import csv
        import time
        from selenium import webdriver

        class ColdWellSpider(BaseSpider):
            name = "cwspider"
            allowed_domains = ["coldwellbankerhomes.com"]
            #start_urls = [''.join(row).strip() for row in csv.reader(open("remaining_links.csv"))]
            #start_urls = ['https://www.coldwellbankerhomes.com/fl/boynton-beach/5451-verona-drive-unit-d/pid_9266204/']
            start_urls = ['https://www.coldwellbankerhomes.com/fl/miami-dade-county/kvc-17_1,17_3,17_2,17_8/incl-22/']
            def parse(self,response):
                    #browser = webdriver.PhantomJS(service_args=['--ignore-ssl-errors=true', '--load-images=false'])
                    browser = webdriver.Firefox()
                    browser.maximize_window()
                    browser.get(response.url)
                    time.sleep(5)
                    #to extract all the links from a page and send request to those links
                    self.getlink(response)
                    #for clicking the load more button in the page 
                    while True:
                        try:
                            browser.find_element_by_class_name('search-results-load-more').find_element_by_tag_name('a').click()
                            time.sleep(3)
                            self.getlink(browser)
                        except:
                            break
            def getlink(self,response):
                print 'hhelo'
                c = open('data_getlink.csv', 'a')
                d = csv.writer(c, lineterminator='n')
                print 'hello2'
                listclass = response.xpath('//div[@class="list-items"]/div[contains(@id,"snapshot")]')
                for l in listclass:
                       link = 'http://www.coldwellbankerhomes.com/'+''.join(l.xpath('./h2/a/@href').extract())
                       d.writerow([link])
                       yield Request(url = str(link),callback=self.parse_link)

           #callback function of Request
           def parse_link(self,response):
                    b = open('data_parselink.csv', 'a')
                    a = csv.writer(b, lineterminator='n')
                    a.writerow([response.url])

问题出在yield Request(url = str(link),callback=self.parse_link)上。当我删除这行代码时，getlink函数被完美地调用，链接被写入data_getlink.csv文件。但是，如果代码中存在上述行，则不会调用整个getlink函数，因此也不会调用回调函数。任何帮助都是非常有用的

Answer 1

问题出在yield语句上。

当存在yield语句时，getlink函数将成为迭代器函数，因此在请求第一个迭代项之前不会执行其主体。

要解决此问题，请通过以下方式调用getlink函数：

for i in self.getlink(browser): # actually, browser or response here?
    yield i

或蟒蛇3:

yield from self.getlink(browser)