标签：average add sage 逻辑 info ips item 对象传递 抽取
通过下面的命令可以快速创建 CrawlSpider模板 的代码：
scrapy genspider -t crawl tencent tencent.com
上一个案例中，我们通过正则表达式，制作了新的url作为Request请求参数，现在我们可以换个花样...
class scrapy.spiders.CrawlSpider
它是Spider的派生类，Spider类的设计原则是只爬取start_url列表中的网页，而CrawlSpider类定义了一些规则(rule)来提供跟进link的方便的机制，从爬取的网页中获取link并继续爬取的工作更适合。
class CrawlSpider(Spider):
rules = ()
def __init__(self, *a, **kw):
super(CrawlSpider, self).__init__(*a, **kw)
self._compile_rules()
#首先调用parse()来处理start_urls中返回的response对象
#parse()则将这些response对象传递给了_parse_response()函数处理，并设置回调函数为parse_start_url()
#设置了跟进标志位True
#parse将返回item和跟进了的Request对象
def parse(self, response):
return self._parse_response(response, self.parse_start_url, cb_kwargs={}, follow=True)
#处理start_url中返回的response，需要重写
def parse_start_url(self, response):
return []
def process_results(self, response, results):
return results
#从response中抽取符合任一用户定义‘规则‘的链接，并构造成Resquest对象返回
def _requests_to_follow(self, response):
if not isinstance(response, HtmlResponse):
return
seen = set()
#抽取之内的所有链接，只要通过任意一个‘规则‘，即表示合法
for n, rule in enumerate(self._rules):
links = [l for l in rule.link_extractor.extract_links(response) if l not in seen]
#使用用户指定的process_links处理每个连接
if links and rule.process_links:
links = rule.process_links(links)
#将链接加入seen集合，为每个链接生成Request对象，并设置回调函数为_repsonse_downloaded()
for link in links:
seen.add(link)
#构造Request对象，并将Rule规则中定义的回调函数作为这个Request对象的回调函数
r = Request(url=link.url, callback=self._response_downloaded)
r.meta.update(rule=n, link_text=link.text)
#对每个Request调用process_request()函数。该函数默认为indentify，即不做任何处理，直接返回该Request.
yield rule.process_request(r)
#处理通过rule提取出的连接，并返回item以及request
def _response_downloaded(self, response):
rule = self._rules[response.meta[‘rule‘]]
return self._parse_response(response, rule.callback, rule.cb_kwargs, rule.follow)
#解析response对象，会用callback解析处理他，并返回request或Item对象
def _parse_response(self, response, callback, cb_kwargs, follow=True):
#首先判断是否设置了回调函数。（该回调函数可能是rule中的解析函数，也可能是 parse_start_url函数）
#如果设置了回调函数（parse_start_url()），那么首先用parse_start_url()处理response对象，
#然后再交给process_results处理。返回cb_res的一个列表
if callback:
#如果是parse调用的，则会解析成Request对象
#如果是rule callback，则会解析成Item
cb_res = callback(response, **cb_kwargs) or ()
cb_res = self.process_results(response, cb_res)
for requests_or_item in iterate_spider_output(cb_res):
yield requests_or_item
#如果需要跟进，那么使用定义的Rule规则提取并返回这些Request对象
if follow and self._follow_links:
#返回每个Request对象
for request_or_item in self._requests_to_follow(response):
yield request_or_item
def _compile_rules(self):
def get_method(method):
if callable(method):
return method
elif isinstance(method, basestring):
return getattr(self, method, None)
self._rules = [copy.copy(r) for r in self.rules]
for rule in self._rules:
rule.callback = get_method(rule.callback)
rule.process_links = get_method(rule.process_links)
rule.process_request = get_method(rule.process_request)
def set_crawler(self, crawler):
super(CrawlSpider, self).set_crawler(crawler)
self._follow_links = crawler.settings.getbool(‘CRAWLSPIDER_FOLLOW_LINKS‘, True)
Link Extractors 的目的很简单: 提取链接?
每个LinkExtractor有唯一的公共方法是 extract_links()，它接收一个 Response 对象，并返回一个 scrapy.link.Link 对象。
Link Extractors要实例化一次，并且 extract_links 方法会根据不同的 response 调用多次提取链接?
主要参数
class scrapy.linkextractors.LinkExtractor(
allow = (), # 满足括号中“正则表达式”的值会被提取，如果为空，则全部匹配
deny = (), # 与这个正则表达式(或正则表达式列表)不匹配的URL一定不提取
allow_domains = (), # 会被提取的链接的domains
deny_domains = (), # 一定不会被提取链接的domains
deny_extensions = None,
restrict_xpaths = (), # 使用xpath表达式，和allow共同作用过滤链接（一般只用allow就行了）
tags = (‘a‘,‘area‘),
attrs = (‘href‘),
canonicalize = True,
unique = True,
process_value = None
)
在rules中包含一个或多个Rule对象，每个Rule对爬取网站的动作定义了特定操作。如果多个rule匹配了相同的链接，则根据规则在本集合中被定义的顺序，第一个会被使用。
主要参数
class scrapy.spiders.Rule(
link_extractor,
callback = None,
cb_kwargs = None,
follow = None,
process_links = None,
process_request = None
)
link_extractor：是一个Link Extractor对象，用于定义需要提取的链接。
callback： 从link_extractor中每获取到链接时，参数所指定的值作为回调函数，该回调函数接受一个response作为其第一个参数。
注意：当编写爬虫规则时，避免使用parse作为回调函数。由于CrawlSpider使用parse方法来实现其逻辑，如果覆盖了 parse方法，crawl spider将会运行失败。
follow：是一个布尔(boolean)值，指定了根据该规则从response提取的链接是否需要跟进。 如果callback为None，follow 默认设置为True ，否则默认为False。
process_links：指定该spider中哪个的函数将会被调用，从link_extractor中获取到链接列表时将会调用该函数。该方法主要用来过滤。
process_request：指定该spider中哪个的函数将会被调用， 该规则提取到每个request时都会调用该函数。 (用来过滤request)
小Tips
由于CrawlSpider使用parse方法来实现其逻辑，如果覆盖了 parse方法，crawl spider将会运行失败。
Scrapy提供了log功能，可以通过 logging 模块使用。
可以修改配置文件settings.py，任意位置添加下面两行。
LOG_FILE = "TencentSpider.log"
LOG_LEVEL = "INFO"
Scrapy提供5层logging级别:
CRITICAL - 严重错误(critical)
通过在setting.py中进行以下设置可以被用来配置logging:
LOG_ENABLED 默认: True，启用loggingLOG_ENCODING 默认: ‘utf-8‘，logging使用的编码LOG_FILE 默认: None，在当前目录里创建logging输出文件的文件名LOG_LEVEL 默认: ‘DEBUG‘，log的最低级别LOG_STDOUT 默认: False 如果为 True，进程所有的标准输出(及错误)将会被重定向到log中。例如，执行 print "hello" ，其将会在Scrapy log中显示。示例1、使用CrawlSpider爬取腾讯招聘网站
爬虫模块
# -*- coding: utf-8 -*-
import scrapy
from scrapy.linkextractors import LinkExtractor # 导入链接规则匹配类，用来提取符合规则的连接
from scrapy.spiders import CrawlSpider, Rule # 导入CrawlSpider类和Rule
from day_31.TencentCrawlSpider.TencentCrawlSpider.items import TencentcrawlspiderItem
class TencentSpider(CrawlSpider):
name = ‘tencent‘
allowed_domains = [‘tencent.com‘]
start_urls = [‘http://hr.tencent.com/position.php?&start=0‘]
rules = (
Rule(LinkExtractor(allow=r‘position\.php\?&start=\d+#a‘), callback=‘parse_item‘, follow=True),
# Response里链接的提取规则，返回的符合匹配规则的链接匹配对象的列表
# 获取这个列表里的链接，依次发送请求，并且继续跟进，调用指定回调函数处理
# 前面加r表示将正则表达式编译成一个规则的对象
)
# 指定的回调函数
def parse_item(self, response):
for i in response.xpath(‘//tr[@class="even"] | //tr[@class="odd"]‘):
item = TencentcrawlspiderItem()
item[‘name‘] = i.xpath(".//a/text()").extract()[0]
item[‘link‘] = i.xpath(".//a/@href").extract()[0]
item[‘type‘] = i.xpath("./td[2]/text()").extract()[0]
item[‘number‘] = i.xpath(".//td[3]/text()").extract()[0]
item[‘place‘] = i.xpath(".//td[4]/text()").extract()[0]
item[‘rtime‘] = i.xpath(".//td[5]/text()").extract()[0]
yield item
管道模块
# -*- coding: utf-8 -*-
# Define your item pipelines here
#
# Don‘t forget to add your pipeline to the ITEM_PIPELINES setting
# See: http://doc.scrapy.org/en/latest/topics/item-pipeline.html
import json
class TencentcrawlspiderPipeline(object):
def __init__(self):
self.file = open(‘tencent-job.json‘,‘wb‘)
def process_item(self, item, spider):
text = json.dumps(dict(item),ensure_ascii=False)+‘\n‘
self.file.write(text.encode(‘utf-8‘))
return item
def close_spider(self, spider):
self.file.close()
1 import scrapy 2 3 class TencentcrawlspiderItem(scrapy.Item): 4 # define the fields for your item here like: 5 name = scrapy.Field() 6 link = scrapy.Field() 7 type = scrapy.Field() 8 number = scrapy.Field() 9 place = scrapy.Field() 10 rtime = scrapy.Field()
1 # -*- coding: utf-8 -*- 2 3 # Scrapy settings for TencentCrawlSpider project 4 # 5 # For simplicity, this file contains only settings considered important or 6 # commonly used. You can find more settings consulting the documentation: 7 # 8 # http://doc.scrapy.org/en/latest/topics/settings.html 9 # http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html 10 # http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html 11 12 BOT_NAME = ‘TencentCrawlSpider‘ 13 14 SPIDER_MODULES = [‘TencentCrawlSpider.spiders‘] 15 NEWSPIDER_MODULE = ‘TencentCrawlSpider.spiders‘ 16 17 18 # Crawl responsibly by identifying yourself (and your website) on the user-agent 19 #USER_AGENT = ‘TencentCrawlSpider (+http://www.yourdomain.com)‘ 20 21 # Obey robots.txt rules 22 # ROBOTSTXT_OBEY = True 23 24 # Configure maximum concurrent requests performed by Scrapy (default: 16) 25 #CONCURRENT_REQUESTS = 32 26 27 # Configure a delay for requests for the same website (default: 0) 28 # See http://scrapy.readthedocs.org/en/latest/topics/settings.html#download-delay 29 # See also autothrottle settings and docs 30 DOWNLOAD_DELAY = 3 31 # The download delay setting will honor only one of: 32 #CONCURRENT_REQUESTS_PER_DOMAIN = 16 33 #CONCURRENT_REQUESTS_PER_IP = 16 34 35 # Disable cookies (enabled by default) 36 #COOKIES_ENABLED = False 37 38 # Disable Telnet Console (enabled by default) 39 #TELNETCONSOLE_ENABLED = False 40 41 # Override the default request headers: 42 DEFAULT_REQUEST_HEADERS = { 43 ‘User-Agent‘:‘Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0;‘, 44 ‘Accept‘: ‘text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8‘, 45 # ‘Accept-Language‘: ‘en‘, 46 } 47 48 LOG_FILE = ‘tencentlog.txt‘ 49 LOG_LEVEL = ‘DEBUG‘ 50 # Enable or disable spider middlewares 51 # See http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html 52 #SPIDER_MIDDLEWARES = { 53 # ‘TencentCrawlSpider.middlewares.TencentcrawlspiderSpiderMiddleware‘: 543, 54 #} 55 56 # Enable or disable downloader middlewares 57 # See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html 58 #DOWNLOADER_MIDDLEWARES = { 59 # ‘TencentCrawlSpider.middlewares.MyCustomDownloaderMiddleware‘: 543, 60 #} 61 62 # Enable or disable extensions 63 # See http://scrapy.readthedocs.org/en/latest/topics/extensions.html 64 #EXTENSIONS = { 65 # ‘scrapy.extensions.telnet.TelnetConsole‘: None, 66 #} 67 68 # Configure item pipelines 69 # See http://scrapy.readthedocs.org/en/latest/topics/item-pipeline.html 70 ITEM_PIPELINES = { 71 ‘TencentCrawlSpider.pipelines.TencentcrawlspiderPipeline‘: 300, 72 } 73 74 # Enable and configure the AutoThrottle extension (disabled by default) 75 # See http://doc.scrapy.org/en/latest/topics/autothrottle.html 76 #AUTOTHROTTLE_ENABLED = True 77 # The initial download delay 78 #AUTOTHROTTLE_START_DELAY = 5 79 # The maximum download delay to be set in case of high latencies 80 #AUTOTHROTTLE_MAX_DELAY = 60 81 # The average number of requests Scrapy should be sending in parallel to 82 # each remote server 83 #AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0 84 # Enable showing throttling stats for every response received: 85 #AUTOTHROTTLE_DEBUG = False 86 87 # Enable and configure HTTP caching (disabled by default) 88 # See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings 89 #HTTPCACHE_ENABLED = True 90 #HTTPCACHE_EXPIRATION_SECS = 0 91 #HTTPCACHE_DIR = ‘httpcache‘ 92 #HTTPCACHE_IGNORE_HTTP_CODES = [] 93 #HTTPCACHE_STORAGE = ‘scrapy.extensions.httpcache.FilesystemCacheStorage‘
示例二：爬取网页里面的信息（东莞）
爬虫模块
# -*- coding: utf-8 -*-
import scrapy
from scrapy.linkextractors import LinkExtractor
from scrapy.spiders import CrawlSpider, Rule
from day_31.DongguanCrawlSpider.DongguanCrawlSpider.items import DongguancrawlspiderItem
class DongguanSpider(CrawlSpider):
name = ‘dongguan‘
allowed_domains = [‘wz.sun0769.com‘]
start_urls = [‘http://wz.sun0769.com/index.php/question/questionType?type=4&page=0‘]
rules = (
Rule(LinkExtractor(allow=r‘type=4&page=\d+‘)),
Rule(LinkExtractor(allow=r‘question/show\?id=\d+‘), callback=‘parse_item‘, follow=False),
)
def parse_item(self, response):
root = response.xpath("//div[@class=‘pagecenter p3‘]//strong/text()").extract()[0]
item = DongguancrawlspiderItem()
item[‘title‘] = root.split(‘\xa0\xa0‘)[0].split(‘：‘)[-1]
item[‘number‘] = root.split(‘\xa0\xa0‘)[1].split(‘:‘)[-1]
item[‘url‘] = response.url
item[‘content‘] = response.xpath(‘//div[@class="content text14_2"]/div[@class="c1 text14_2"]/text()‘).extract()[0].strip() # 去空格
yield item
管道模块
# -*- coding: utf-8 -*-
# Define your item pipelines here
#
# Don‘t forget to add your pipeline to the ITEM_PIPELINES setting
# See: http://doc.scrapy.org/en/latest/topics/item-pipeline.html
import json
class DongguancrawlspiderPipeline(object):
def __init__(self):
self.file = open(‘dongguan.json‘,‘wb‘)
def process_item(self, item, spider):
text = json.dumps(dict(item),ensure_ascii=False)+‘\n‘
self.file.write(text.encode(‘utf-8‘))
return item
def close_spider(self,spider):
self.file.close()
1 import scrapy 2 3 class DongguancrawlspiderItem(scrapy.Item): 4 # define the fields for your item here like: 5 title = scrapy.Field() 6 content = scrapy.Field() 7 url = scrapy.Field() 8 number = scrapy.Field()
1 # -*- coding: utf-8 -*- 2 3 # Scrapy settings for DongguanCrawlSpider project 4 # 5 # For simplicity, this file contains only settings considered important or 6 # commonly used. You can find more settings consulting the documentation: 7 # 8 # http://doc.scrapy.org/en/latest/topics/settings.html 9 # http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html 10 # http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html 11 12 BOT_NAME = ‘DongguanCrawlSpider‘ 13 14 SPIDER_MODULES = [‘DongguanCrawlSpider.spiders‘] 15 NEWSPIDER_MODULE = ‘DongguanCrawlSpider.spiders‘ 16 17 18 # Crawl responsibly by identifying yourself (and your website) on the user-agent 19 #USER_AGENT = ‘DongguanCrawlSpider (+http://www.yourdomain.com)‘ 20 21 # Obey robots.txt rules 22 # ROBOTSTXT_OBEY = True 23 24 # Configure maximum concurrent requests performed by Scrapy (default: 16) 25 #CONCURRENT_REQUESTS = 32 26 27 # Configure a delay for requests for the same website (default: 0) 28 # See http://scrapy.readthedocs.org/en/latest/topics/settings.html#download-delay 29 # See also autothrottle settings and docs 30 #DOWNLOAD_DELAY = 3 31 # The download delay setting will honor only one of: 32 #CONCURRENT_REQUESTS_PER_DOMAIN = 16 33 #CONCURRENT_REQUESTS_PER_IP = 16 34 35 # Disable cookies (enabled by default) 36 #COOKIES_ENABLED = False 37 38 # Disable Telnet Console (enabled by default) 39 #TELNETCONSOLE_ENABLED = False 40 41 # Override the default request headers: 42 DEFAULT_REQUEST_HEADERS = { 43 ‘User-Agent‘:‘Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0;‘, 44 ‘Accept‘: ‘text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8‘, 45 # ‘Accept-Language‘: ‘en‘, 46 } 47 48 LOG_FILE = ‘dongguan.log‘ 49 LOG_LEVER = ‘DEBUG‘ 50 51 # Enable or disable spider middlewares 52 # See http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html 53 #SPIDER_MIDDLEWARES = { 54 # ‘DongguanCrawlSpider.middlewares.DongguancrawlspiderSpiderMiddleware‘: 543, 55 #} 56 57 # Enable or disable downloader middlewares 58 # See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html 59 #DOWNLOADER_MIDDLEWARES = { 60 # ‘DongguanCrawlSpider.middlewares.MyCustomDownloaderMiddleware‘: 543, 61 #} 62 63 # Enable or disable extensions 64 # See http://scrapy.readthedocs.org/en/latest/topics/extensions.html 65 #EXTENSIONS = { 66 # ‘scrapy.extensions.telnet.TelnetConsole‘: None, 67 #} 68 69 # Configure item pipelines 70 # See http://scrapy.readthedocs.org/en/latest/topics/item-pipeline.html 71 ITEM_PIPELINES = { 72 ‘DongguanCrawlSpider.pipelines.DongguancrawlspiderPipeline‘: 300, 73 } 74 75 # Enable and configure the AutoThrottle extension (disabled by default) 76 # See http://doc.scrapy.org/en/latest/topics/autothrottle.html 77 #AUTOTHROTTLE_ENABLED = True 78 # The initial download delay 79 #AUTOTHROTTLE_START_DELAY = 5 80 # The maximum download delay to be set in case of high latencies 81 #AUTOTHROTTLE_MAX_DELAY = 60 82 # The average number of requests Scrapy should be sending in parallel to 83 # each remote server 84 #AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0 85 # Enable showing throttling stats for every response received: 86 #AUTOTHROTTLE_DEBUG = False 87 88 # Enable and configure HTTP caching (disabled by default) 89 # See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings 90 #HTTPCACHE_ENABLED = True 91 #HTTPCACHE_EXPIRATION_SECS = 0 92 #HTTPCACHE_DIR = ‘httpcache‘ 93 #HTTPCACHE_IGNORE_HTTP_CODES = [] 94 #HTTPCACHE_STORAGE = ‘scrapy.extensions.httpcache.FilesystemCacheStorage‘
标签：average add sage 逻辑 info ips item 对象传递 抽取
原文地址：http://www.cnblogs.com/x54256/p/7979127.html
