Question

我尝试抓取多个网址，抓取多个网页。我正在使用维基百科进行测试，为了更容易，我只为每个页面使用了相同的Xpath选择器，但我最终想要使用每个页面独有的许多不同的Xpath选择器，因此每个页面都有自己独立的parsePage方法。

当我不使用项目加载器并且直接填充项目时，此代码非常有效。当我使用项目加载器时，这些项目被奇怪地填充，它似乎完全忽略了在parse方法中分配的回调，并且只使用了start_urls用于parsePage方法。

import scrapy
from scrapy.http import Request
from scrapy import Spider, Request, Selector
from testanother.items import TestItems, TheLoader

class tester(scrapy.Spider):
name = 'vs'
handle_httpstatus_list = [404, 200, 300]
#Usually, I only get data from the first start url
start_urls = ['https://en.wikipedia.org/wiki/SANZAAR','https://en.wikipedia.org/wiki/2016_Rugby_Championship','https://en.wikipedia.org/wiki/2016_Super_Rugby_season']
def parse(self, response):
   #item = TestItems()
    l = TheLoader(item=TestItems(), response=response)
    #when I use an item loader, the url in the request is completely ignored. without the item loader, it works properly.
    request = Request("https://en.wikipedia.org/wiki/2016_Rugby_Championship", callback=self.parsePage1, meta={'loadernext':l}, dont_filter=True)
    yield request

    request = Request("https://en.wikipedia.org/wiki/SANZAAR", callback=self.parsePage2, meta={'loadernext1': l}, dont_filter=True)
    yield request

    yield Request("https://en.wikipedia.org/wiki/2016_Super_Rugby_season", callback=self.parsePage3, meta={'loadernext2': l}, dont_filter=True)

def parsePage1(self,response):
    loadernext = response.meta['loadernext']
    loadernext.add_xpath('title1', '//*[@id="firstHeading"]/text()')
    return loadernext.load_item()
#I'm not sure if this return and load_item is the problem, because I've tried yielding/returning to another method that does the item loading instead and the first start url is still the only url scraped. 
def parsePage2(self,response):
    loadernext1 = response.meta['loadernext1']
    loadernext1.add_xpath('title2', '//*[@id="firstHeading"]/text()')
    return loadernext1.load_item()

def parsePage3(self,response):
    loadernext2 = response.meta['loadernext2']
    loadernext2.add_xpath('title3', '//*[@id="firstHeading"]/text()')
    return loadernext2.load_item()

以下是我不使用项目加载器时的结果：

{'title1': [u'2016 Rugby Championship'],
 'title': [u'SANZAAR'],
 'title3': [u'2016 Super Rugby season']}

这里是项目加载器的一小部分日志：

{'title2': u'SANZAAR'}
2016-09-24 14:30:43 [scrapy] DEBUG: Crawled (200) <GET https://en.wikipedia.org/wiki/2016_Rugby_Championship> (referer: https://en.wikipedia.org/wiki/SANZAAR)
2016-09-24 14:30:43 [scrapy] DEBUG: Crawled (200) <GET https://en.wikipedia.org/wiki/2016_Rugby_Championship> (referer: https://en.wikipedia.org/wiki/2016_Rugby_Championship)
2016-09-24 14:30:43 [scrapy] DEBUG: Scraped from <200 https://en.wikipedia.org/wiki/2016_Super_Rugby_season>
{'title2': u'SANZAAR', 'title3': u'SANZAAR'}
2016-09-24 14:30:43 [scrapy] DEBUG: Crawled (200) <GET https://en.wikipedia.org/wiki/SANZAAR> (referer: https://en.wikipedia.org/wiki/2016_Rugby_Championship)
2016-09-24 14:30:43 [scrapy] DEBUG: Crawled (200) <GET https://en.wikipedia.org/wiki/2016_Rugby_Championship> (referer: https://en.wikipedia.org/wiki/2016_Super_Rugby_season)
2016-09-24 14:30:43 [scrapy] DEBUG: Crawled (200) <GET https://en.wikipedia.org/wiki/2016_Super_Rugby_season> (referer: https://en.wikipedia.org/wiki/2016_Rugby_Championship)
2016-09-24 14:30:43 [scrapy] DEBUG: Crawled (200) <GET https://en.wikipedia.org/wiki/2016_Super_Rugby_season> (referer: https://en.wikipedia.org/wiki/2016_Super_Rugby_season)
2016-09-24 14:30:43 [scrapy] DEBUG: Scraped from <200 https://en.wikipedia.org/wiki/2016_Rugby_Championship>
{'title1': u'SANZAAR', 'title2': u'SANZAAR', 'title3': u'SANZAAR'}
2016-09-24 14:30:43 [scrapy] DEBUG: Scraped from <200 https://en.wikipedia.org/wiki/2016_Rugby_Championship>
{'title1': u'2016 Rugby Championship'}
2016-09-24 14:30:43 [scrapy] DEBUG: Scraped from <200 https://en.wikipedia.org/wiki/SANZAAR>
{'title1': u'2016 Rugby Championship', 'title2': u'2016 Rugby Championship'}
2016-09-24 14:30:43 [scrapy] DEBUG: Scraped from <200 https://en.wikipedia.org/wiki/2016_Rugby_Championship>
{'title1': u'2016 Super Rugby season'}
2016-09-24 14:30:43 [scrapy] DEBUG: Crawled (200) <GET https://en.wikipedia.org/wiki/SANZAAR> (referer: https://en.wikipedia.org/wiki/2016_Super_Rugby_season)
2016-09-24 14:30:43 [scrapy] DEBUG: Scraped from <200 https://en.wikipedia.org/wiki/2016_Super_Rugby_season>
{'title1': u'2016 Rugby Championship',
 'title2': u'2016 Rugby Championship',
 'title3': u'2016 Rugby Championship'}
2016-09-24 14:30:43 [scrapy] DEBUG: Scraped from <200 https://en.wikipedia.org/wiki/2016_Super_Rugby_season>
{'title1': u'2016 Super Rugby season', 'title3': u'2016 Super Rugby season'}
2016-09-24 14:30:43 [scrapy] DEBUG: Scraped from <200 https://en.wikipedia.org/wiki/SANZAAR>
{'title1': u'2016 Super Rugby season',
 'title2': u'2016 Super Rugby season',
 'title3': u'2016 Super Rugby season'}
 2016-09-24 14:30:43 [scrapy] INFO: Clos

到底出了什么问题？谢谢！

Answer 1

一个问题是您将同一个项目加载程序实例的多个引用传递给多个回调，例如yield request中有两条parse条说明。

此外，在后续回调中，加载程序仍在使用旧的response对象，例如在parsePage1中，项目加载器仍然在response parse上运行。

在大多数情况下，建议不要将项目加载器传递给另一个回调。或者，您可能会发现直接传递项目对象更好。

这是一个简短（不完整）的例子，通过编辑代码：

def parse(self, response):
    l = TheLoader(item=TestItems(), response=response)
    request = Request(
        "https://en.wikipedia.org/wiki/2016_Rugby_Championship",
        callback=self.parsePage1,
        meta={'item': l.load_item()},
        dont_filter=True
    )
    yield request

def parsePage1(self,response):
    loadernext = TheLoader(item=response.meta['item'], response=response)
    loadernext.add_xpath('title1', '//*[@id="firstHeading"]/text()')
    return loadernext.load_item()

Scrapy：在多个页面上使用项目加载器填充项目

1 个答案: