我试图在Scrapy中创建自定义DUPEFILTER_CLASS，但它似乎无法正常工作。这是我的蜘蛛示例：
import scrapy
from tutorial.items import QuoteItem
class QuotesSpider(scrapy.Spider):
name = "quotes"
start_urls = [
'http://quotes.toscrape.com/page/1/',
'http://quotes.toscrape.com/page/2/',
]
custom_settings = {
'DUPEFILTER_CLASS': 'tutorial.dupefilter.RedisDupeFilter',
}
def parse(self, response):
for quote in response.css('div.quote'):
item = QuoteItem()
item['text'] = quote.css('span.text::text').extract_first()
item['author'] = quote.css('small.author::text').extract_first()
item['tags'] = quote.css('div.tags a.tag::text').extract()
yield item
其中items.py是
import scrapy
class QuoteItem(scrapy.Item):
text = scrapy.Field()
author = scrapy.Field()
tags = scrapy.Field()
和目录树中dupefilter.py旁边的items.py是
import logging
import redis
import scrapy.dupefilters
class RedisDupeFilter(scrapy.dupefilters.BaseDupeFilter):
def __init__(self, server, key):
self.server = server
self.key = key
self.logger = logging.getLogger(__name__)
@classmethod
def from_settings(cls, settings):
server = redis.Redis()
key = "URLs_seen"
return cls(server=server, key=key)
def request_seen(self, request):
self.logger.debug("Checking whether request {request} has been seen yet...".format(request=request))
added = self.server.sadd(self.key, request.url)
return added == 0
在运行蜘蛛之前，我在命令行使用redis-server启动了Redis。然后在项目目录中，我使用
scrapy crawl quotes
并观察以下日志输出：
2017-05-05 12:45:15 [scrapy.utils.log] INFO: Scrapy 1.3.3 started (bot: tutorial)
2017-05-05 12:45:15 [scrapy.utils.log] INFO: Overridden settings: {'NEWSPIDER_MODULE': 'tutorial.spiders', 'SPIDER_MODULES': ['tutorial.spiders'], 'ROBOTSTXT_OBEY': True, 'BOT_NAME': 'tutorial'}
2017-05-05 12:45:15 [scrapy.middleware] INFO: Enabled extensions:
['scrapy.extensions.logstats.LogStats',
'scrapy.extensions.telnet.TelnetConsole',
'scrapy.extensions.corestats.CoreStats']
2017-05-05 12:45:15 [scrapy.middleware] INFO: Enabled downloader middlewares:
['scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware',
'scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',
'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',
'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',
'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',
'scrapy.downloadermiddlewares.retry.RetryMiddleware',
'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',
'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',
'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',
'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',
'scrapy.downloadermiddlewares.stats.DownloaderStats']
2017-05-05 12:45:15 [scrapy.middleware] INFO: Enabled spider middlewares:
['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',
'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',
'scrapy.spidermiddlewares.referer.RefererMiddleware',
'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',
'scrapy.spidermiddlewares.depth.DepthMiddleware']
2017-05-05 12:45:15 [scrapy.middleware] INFO: Enabled item pipelines:
[]
2017-05-05 12:45:15 [scrapy.core.engine] INFO: Spider opened
2017-05-05 12:45:15 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2017-05-05 12:45:15 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023
2017-05-05 12:45:15 [scrapy.core.engine] DEBUG: Crawled (404) <GET http://quotes.toscrape.com/robots.txt> (referer: None)
2017-05-05 12:45:15 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://quotes.toscrape.com/page/1/> (referer: None)
2017-05-05 12:45:15 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://quotes.toscrape.com/page/2/> (referer: None)
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'author': u'Albert Einstein',
'tags': [u'change', u'deep-thoughts', u'thinking', u'world'],
'text': u'\u201cThe world as we have created it is a process of our thinking. It cannot be changed without changing our thinking.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'author': u'J.K. Rowling',
'tags': [u'abilities', u'choices'],
'text': u'\u201cIt is our choices, Harry, that show what we truly are, far more than our abilities.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'author': u'Albert Einstein',
'tags': [u'inspirational', u'life', u'live', u'miracle', u'miracles'],
'text': u'\u201cThere are only two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'author': u'Jane Austen',
'tags': [u'aliteracy', u'books', u'classic', u'humor'],
'text': u'\u201cThe person, be it gentleman or lady, who has not pleasure in a good novel, must be intolerably stupid.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'author': u'Marilyn Monroe',
'tags': [u'be-yourself', u'inspirational'],
'text': u"\u201cImperfection is beauty, madness is genius and it's better to be absolutely ridiculous than absolutely boring.\u201d"}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'author': u'Albert Einstein',
'tags': [u'adulthood', u'success', u'value'],
'text': u'\u201cTry not to become a man of success. Rather become a man of value.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'author': u'Andr\xe9 Gide',
'tags': [u'life', u'love'],
'text': u'\u201cIt is better to be hated for what you are than to be loved for what you are not.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'author': u'Thomas A. Edison',
'tags': [u'edison', u'failure', u'inspirational', u'paraphrased'],
'text': u"\u201cI have not failed. I've just found 10,000 ways that won't work.\u201d"}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'author': u'Eleanor Roosevelt',
'tags': [u'misattributed-eleanor-roosevelt'],
'text': u"\u201cA woman is like a tea bag; you never know how strong it is until it's in hot water.\u201d"}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'author': u'Steve Martin',
'tags': [u'humor', u'obvious', u'simile'],
'text': u'\u201cA day without sunshine is like, you know, night.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/2/>
{'author': u'Marilyn Monroe',
'tags': [u'friends',
u'heartbreak',
u'inspirational',
u'life',
u'love',
u'sisters'],
'text': u"\u201cThis life is what you make it. No matter what, you're going to mess up sometimes, it's a universal truth. But the good part is you get to decide how you're going to mess it up. Girls will be your friends - they'll act like it anyway. But just remember, some come, some go. The ones that stay with you through everything - they're your true best friends. Don't let go of them. Also remember, sisters make the best friends in the world. As for lovers, well, they'll come and go too. And baby, I hate to say it, most of them - actually pretty much all of them are going to break your heart, but you can't give up because if you give up, you'll never find your soulmate. You'll never find that half who makes you whole and that goes for everything. Just because you fail once, doesn't mean you're gonna fail at everything. Keep trying, hold on, and always, always, always believe in yourself, because if you don't, then who will, sweetie? So keep your head high, keep your chin up, and most importantly, keep smiling, because life's a beautiful thing and there's so much to smile about.\u201d"}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/2/>
{'author': u'J.K. Rowling',
'tags': [u'courage', u'friends'],
'text': u'\u201cIt takes a great deal of bravery to stand up to our enemies, but just as much to stand up to our friends.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/2/>
{'author': u'Albert Einstein',
'tags': [u'simplicity', u'understand'],
'text': u"\u201cIf you can't explain it to a six year old, you don't understand it yourself.\u201d"}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/2/>
{'author': u'Bob Marley',
'tags': [u'love'],
'text': u"\u201cYou may not be her first, her last, or her only. She loved before she may love again. But if she loves you now, what else matters? She's not perfect\u2014you aren't either, and the two of you may never be perfect together but if she can make you laugh, cause you to think twice, and admit to being human and making mistakes, hold onto her and give her the most you can. She may not be thinking about you every second of the day, but she will give you a part of her that she knows you can break\u2014her heart. So don't hurt her, don't change her, don't analyze and don't expect more than she can give. Smile when she makes you happy, let her know when she makes you mad, and miss her when she's not there.\u201d"}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/2/>
{'author': u'Dr. Seuss',
'tags': [u'fantasy'],
'text': u'\u201cI like nonsense, it wakes up the brain cells. Fantasy is a necessary ingredient in living.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/2/>
{'author': u'Douglas Adams',
'tags': [u'life', u'navigation'],
'text': u'\u201cI may not have gone where I intended to go, but I think I have ended up where I needed to be.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/2/>
{'author': u'Elie Wiesel',
'tags': [u'activism',
u'apathy',
u'hate',
u'indifference',
u'inspirational',
u'love',
u'opposite',
u'philosophy'],
'text': u"\u201cThe opposite of love is not hate, it's indifference. The opposite of art is not ugliness, it's indifference. The opposite of faith is not heresy, it's indifference. And the opposite of life is not death, it's indifference.\u201d"}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/2/>
{'author': u'Friedrich Nietzsche',
'tags': [u'friendship',
u'lack-of-friendship',
u'lack-of-love',
u'love',
u'marriage',
u'unhappy-marriage'],
'text': u'\u201cIt is not a lack of love, but a lack of friendship that makes unhappy marriages.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/2/>
{'author': u'Mark Twain',
'tags': [u'books', u'contentment', u'friends', u'friendship', u'life'],
'text': u'\u201cGood friends, good books, and a sleepy conscience: this is the ideal life.\u201d'}
2017-05-05 12:45:15 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/2/>
{'author': u'Allen Saunders',
'tags': [u'fate',
u'life',
u'misattributed-john-lennon',
u'planning',
u'plans'],
'text': u'\u201cLife is what happens to us while we are making other plans.\u201d'}
2017-05-05 12:45:15 [scrapy.core.engine] INFO: Closing spider (finished)
2017-05-05 12:45:15 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 675,
'downloader/request_count': 3,
'downloader/request_method_count/GET': 3,
'downloader/response_bytes': 5976,
'downloader/response_count': 3,
'downloader/response_status_count/200': 2,
'downloader/response_status_count/404': 1,
'finish_reason': 'finished',
'finish_time': datetime.datetime(2017, 5, 5, 10, 45, 15, 881028),
'item_scraped_count': 20,
'log_count/DEBUG': 24,
'log_count/INFO': 7,
'response_received_count': 3,
'scheduler/dequeued': 2,
'scheduler/dequeued/memory': 2,
'scheduler/enqueued': 2,
'scheduler/enqueued/memory': 2,
'start_time': datetime.datetime(2017, 5, 5, 10, 45, 15, 553906)}
2017-05-05 12:45:15 [scrapy.core.engine] INFO: Spider closed (finished)
令我感到困惑的是，我在"Checking whether request ... has been seen yet..." self.logger.debug方法request_seen调用了RedisDupeFilter 。简而言之，我没有看到dupefilter是否真正起作用。 （可能不是，因为如果我再次运行crawl，我会看到相同的输出。）
如何让自定义DUPEFILTER_CLASS生效？
答案 0 :(得分：0)
关注paul trmbrth的评论，而不是使用start_urls类变量，而是覆盖了Scrapy Tutorial中的start_requests方法：
import scrapy
from tutorial.items import QuoteItem
class QuotesSpider(scrapy.Spider):
name = "quotes"
custom_settings = {'DUPEFILTER_CLASS': 'tutorial.dupefilter.RedisDupeFilter'}
def start_requests(self):
urls = [
'http://quotes.toscrape.com/page/1/',
'http://quotes.toscrape.com/page/2/',
]
for url in urls:
yield scrapy.Request(url=url, callback=self.parse)
def parse(self, response):
for quote in response.css('div.quote'):
item = QuoteItem()
item['text'] = quote.css('span.text::text').extract_first()
item['author'] = quote.css('small.author::text').extract_first()
item['tags'] = quote.css('div.tags a.tag::text').extract()
yield item
这使用了dont_filter对象的构造函数中Request的默认值为False的事实（参见https://doc.scrapy.org/en/latest/topics/request-response.html#request-objects）。
dupefilter现在正常工作（假设redis服务器正在后台运行）：第二次scrapy crawl quotes没有任何内容被删除。