1. 可以使用API从脚本运行Scrapy,而不是运行Scrapy的典型方法scrapy crawl;Scrapy是基于Twisted异步网络库构建的,因此需要在Twisted容器内运行它,可以通过两个API来运行单个或多个爬虫scrapy.crawler.CrawlerProcess、scrapy.crawler.CrawlerRunner。
2. 启动爬虫的的第一个实用程序是scrapy.crawler.CrawlerProcess 。该类将为您启动Twisted reactor,配置日志记录并设置关闭处理程序,此类是所有Scrapy命令使用的类。
示例运行单个爬虫:
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import
scrapyfromscrapy.crawlerimport CrawlerProcessclass MySpider(scrapy.Spider):
# Your spider definition ...
process = CrawlerProcess({
'USER_AGENT':'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)'})
process.crawl(MySpider)
process.start() # the script will block here until the crawling is finished
通过CrawlerProcess传入参数,并使用get_project_settings获取Settings 项目设置的实例。
fromscrapy.crawlerimport CrawlerProcessfromscrapy.utils.projectimport get_project_settings
process = CrawlerProcess(get_project_settings())# 'followall' is the name of one of the spiders of the project.process.crawl('followall', domain='scrapinghub.com')
process.start() # the script will block here until the crawling is finished
还有另一个Scrapy实例方式可以更好地控制爬虫运行过程:scrapy.crawler.CrawlerRunner。此类封装了一些简单的帮助程序来运行多个爬虫程序,但它不会以任何方式启动或干扰现有的爬虫。
使用此类,显式运行reactor。如果已有爬虫在运行想在同一个进程中开启另一个Scrapy,建议您使用CrawlerRunner 而不是CrawlerProcess。
注意,爬虫结束后需要手动关闭Twisted reactor,通过向CrawlerRunner.crawl方法返回的延迟添加回调来实现。
下面是它的用法示例,在MySpider完成运行后手动停止容器的回调。
fromtwisted.internetimport reactorimport scrapyfromscrapy.crawlerimport CrawlerRunnerfromscrapy.utils.logimport configure_loggingclass MySpider(scrapy.Spider):
# Your spider definition ...
configure_logging({'LOG_FORMAT':'%(levelname)s: %(message)s'})
runner = CrawlerRunner()
d = runner.crawl(MySpider)
d.addBoth(lambda _: reactor.stop())
reactor.run() # the script will block here until the crawling is finished
在同一个进程中运行多个蜘蛛
默认情况下,Scrapy在您运行时为每个进程运行一个蜘蛛。但是,Scrapy支持使用内部API为每个进程运行多个蜘蛛。
这是一个同时运行多个蜘蛛的示例:
import scrapyfromscrapy.crawlerimport CrawlerProcessclass MySpider1(scrapy.Spider):
# Your first spider definition ...class MySpider2(scrapy.Spider):
# Your second spider definition ...
process = CrawlerProcess()
process.crawl(MySpider1)
process.crawl(MySpider2)
process.start() # the script will block here until all crawling jobs are finished
使用CrawlerRunner示例:
import scrapyfromtwisted.internetimport reactorfromscrapy.crawlerimport CrawlerRunnerfromscrapy.utils.logimport configure_loggingclass MySpider1(scrapy.Spider):
# Your first spider definition ...class MySpider2(scrapy.Spider):
# Your second spider definition ...
configure_logging()
runner = CrawlerRunner()
runner.crawl(MySpider1)
runner.crawl(MySpider2)
d = runner.join()
d.addBoth(lambda _: reactor.stop())
reactor.run() # the script will block here until all crawling jobs are finished
相同的示例,但通过异步运行爬虫蛛:
fromtwisted.internetimport reactor, deferfromscrapy.crawlerimport CrawlerRunnerfromscrapy.utils.logimport configure_loggingclass MySpider1(scrapy.Spider):
# Your first spider definition ...class MySpider2(scrapy.Spider):
# Your second spider definition ...
configure_logging()
runner = CrawlerRunner()
@defer.inlineCallbacksdef crawl():
yield runner.crawl(MySpider1)
yield runner.crawl(MySpider2)
reactor.stop()
crawl()
reactor.run() # the script will block here until the last crawl call is finished