剧本(下)来自this教程包含两个start_urls
.
from scrapy.spider import Spider
from scrapy.selector import Selector
from dirbot.items import Website
class DmozSpider(Spider):
name = "dmoz"
allowed_domains = ["dmoz.org"]
start_urls = [
"http://www.dmoz.org/Computers/Programming/Languages/Python/Books/",
"http://www.dmoz.org/Computers/Programming/Languages/Python/Resources/",
]
def parse(self, response):
"""
The lines below is a spider contract. For more info see:
http://doc.scrapy.org/en/latest/topics/contracts.html
@url http://www.dmoz.org/Computers/Programming/Languages/Python/Resources/
@scrapes name
"""
sel = Selector(response)
sites = sel.xpath('//ul[@class="directory-url"]/li')
items = []
for site in sites:
item = Website()
item['name'] = site.xpath('a/text()').extract()
item['url'] = site.xpath('a/@href').extract()
item['description'] = site.xpath('text()').re('-\s[^\n]*\\r')
items.append(item)
return items
但为什么它只抓取这两个网页呢?我懂了allowed_domains = ["dmoz.org"]
但这两个页面还包含指向其他页面的链接dmoz.org
领域!为什么它不把它们也刮掉呢?
start_urls
class 属性包含起始 url - 仅此而已。如果您提取了要抓取的其他页面的网址 - 收益parse
使用 [another] 回调回调相应的请求:
class Spider(BaseSpider):
name = 'my_spider'
start_urls = [
'http://www.domain.com/'
]
allowed_domains = ['domain.com']
def parse(self, response):
'''Parse main page and extract categories links.'''
hxs = HtmlXPathSelector(response)
urls = hxs.select("//*[@id='tSubmenuContent']/a[position()>1]/@href").extract()
for url in urls:
url = urlparse.urljoin(response.url, url)
self.log('Found category url: %s' % url)
yield Request(url, callback = self.parseCategory)
def parseCategory(self, response):
'''Parse category page and extract links of the items.'''
hxs = HtmlXPathSelector(response)
links = hxs.select("//*[@id='_list']//td[@class='tListDesc']/a/@href").extract()
for link in links:
itemLink = urlparse.urljoin(response.url, link)
self.log('Found item link: %s' % itemLink, log.DEBUG)
yield Request(itemLink, callback = self.parseItem)
def parseItem(self, response):
...
如果您仍然想自定义启动请求创建,请重写方法BaseSpider.start_requests()
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