mirror of https://github.com/scrapy/scrapy.git
104 lines
3.5 KiB
Python
104 lines
3.5 KiB
Python
"""
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This modules implements the CrawlSpider which is the recommended spider to use
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for scraping typical web sites that requires crawling pages.
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See documentation in docs/topics/spiders.rst
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"""
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import copy
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import six
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from scrapy.http import Request, HtmlResponse
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from scrapy.utils.spider import iterate_spider_output
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from scrapy.spiders import Spider
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def identity(x):
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return x
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class Rule(object):
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def __init__(self, link_extractor, callback=None, cb_kwargs=None, follow=None, process_links=None, process_request=identity):
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self.link_extractor = link_extractor
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self.callback = callback
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self.cb_kwargs = cb_kwargs or {}
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self.process_links = process_links
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self.process_request = process_request
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if follow is None:
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self.follow = False if callback else True
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else:
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self.follow = follow
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class CrawlSpider(Spider):
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rules = ()
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def __init__(self, *a, **kw):
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super(CrawlSpider, self).__init__(*a, **kw)
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self._compile_rules()
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def parse(self, response):
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return self._parse_response(response, self.parse_start_url, cb_kwargs={}, follow=True)
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def parse_start_url(self, response):
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return []
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def process_results(self, response, results):
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return results
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def _requests_to_follow(self, response):
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if not isinstance(response, HtmlResponse):
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return
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seen = set()
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for n, rule in enumerate(self._rules):
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links = [lnk for lnk in rule.link_extractor.extract_links(response)
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if lnk not in seen]
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if links and rule.process_links:
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links = rule.process_links(links)
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for link in links:
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seen.add(link)
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r = Request(url=link.url, callback=self._response_downloaded)
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r.meta.update(rule=n, link_text=link.text)
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yield rule.process_request(r)
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def _response_downloaded(self, response):
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rule = self._rules[response.meta['rule']]
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return self._parse_response(response, rule.callback, rule.cb_kwargs, rule.follow)
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def _parse_response(self, response, callback, cb_kwargs, follow=True):
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if callback:
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cb_res = callback(response, **cb_kwargs) or ()
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cb_res = self.process_results(response, cb_res)
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for requests_or_item in iterate_spider_output(cb_res):
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yield requests_or_item
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if follow and self._follow_links:
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for request_or_item in self._requests_to_follow(response):
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yield request_or_item
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def _compile_rules(self):
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def get_method(method):
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if callable(method):
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return method
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elif isinstance(method, six.string_types):
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return getattr(self, method, None)
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self._rules = [copy.copy(r) for r in self.rules]
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for rule in self._rules:
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rule.callback = get_method(rule.callback)
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rule.process_links = get_method(rule.process_links)
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rule.process_request = get_method(rule.process_request)
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@classmethod
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def from_crawler(cls, crawler, *args, **kwargs):
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spider = super(CrawlSpider, cls).from_crawler(crawler, *args, **kwargs)
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spider._follow_links = crawler.settings.getbool(
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'CRAWLSPIDER_FOLLOW_LINKS', True)
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return spider
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def set_crawler(self, crawler):
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super(CrawlSpider, self).set_crawler(crawler)
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self._follow_links = crawler.settings.getbool('CRAWLSPIDER_FOLLOW_LINKS', True)
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