python - Scrapy LinkExtractor - 限制每个 URL 抓取的页面数量

Question

我试图在 Scrapy 的 CrawlSpider 中限制每个 URL 的抓取页面数量。我有一个 start_urls 列表，我想对每个 URL 中抓取的页面数量设置限制。一旦达到限制，蜘蛛应该移动到下一个 start_url。

我知道设置中有 DEPTH_LIMIT 参数，但这不是我要找的。

任何帮助都是有用的。

这是我目前拥有的代码:

class MySpider(CrawlSpider):
    name = 'test'
    allowed_domains = domainvarwebsite
    start_urls = httpvarwebsite

    rules = [Rule(LinkExtractor(),
             callback='parse_item',
             follow=True)
            ]

    def parse_item(self, response):
        #here I parse and yield the items I am interested in.

编辑

我试图实现这个，但我得到了 exceptions.SyntaxError: invalid syntax (filter_domain.py, line 20) .对正在发生的事情有什么想法吗？

再次感谢。

filter_domain.py

import urlparse
from collections import defaultdict
from scrapy.exceptions import IgnoreRequest

class FilterDomainbyLimitMiddleware(object):
def __init__(self, domains_to_filter):
    self.domains_to_filter = domains_to_filter
    self.counter = defaultdict(int)

@classmethod
def from_crawler(cls, crawler):
    settings = crawler.settings
    spider_name = crawler.spider.name
    max_to_filter = settings.get('MAX_TO_FILTER')
    o = cls(max_to_filter)
    return o

def process_request(self, request, spider):
    parsed_url = urlparse.urlparse(request.url)
    (LINE 20:) if self.counter.get(parsed_url.netloc, 0) < self.max_to_filter[parsed_url.netloc]):
        self.counter[parsed_url.netloc] += 1
    else:
        raise IgnoreRequest()

settings.py

MAX_TO_FILTER = 30

DOWNLOADER_MIDDLEWARES = {
    'myproject.filter_domain.FilterDomainbyLimitMiddleware' :400,

}

Answer 1

Scrapy 不直接提供这个，但是你可以创建一个自定义的中间件，像这样:

import urlparse
from collections import defaultdict
from scrapy.exceptions import IgnoreRequest

class FilterDomainbyLimitMiddleware(object):
    def __init__(self, domains_to_filter):
        self.domains_to_filter = domains_to_filter
        self.counter = defaultdict(int)

    @classmethod
    def from_crawler(cls, crawler):
        settings = crawler.settings
        spider_name = crawler.spider.name
        domains_to_filter = settings.get('DOMAINS_TO_FILTER')
        o = cls(domains_to_filter)
        return o

    def process_request(self, request, spider):
        parsed_url = urlparse.urlparse(request.url)
        if parsed_url.netloc in self.domains_to_filter:
            if self.counter.get(parsed_url.netloc, 0) < self.domains_to_filter[parsed_url.netloc]):
                self.counter[parsed_url.netloc] += 1
            else:
                raise IgnoreRequest()

并在如下设置中声明 DOMAINS_TO_FILTER:

DOMAINS_TO_FILTER = {
    'mydomain': 5
}

只接受来自该域的 5 个请求。还记得在指定的设置中启用中间件 here