Scrapy-Reactor无法重启

  • Z时代
  • 2024-01-10
  • 分类：问答

与：

from twisted.internet import reactor
from scrapy.crawler import CrawlerProcess

我一直成功地运行了此过程：

process = CrawlerProcess(get_project_settings())
process.crawl(*args)
# the script will block here until the crawling is finished
process.start()

但由于我已将此代码移到一个web_crawler(self)函数中，如下所示：

def web_crawler(self):
    # set up a crawler
    process = CrawlerProcess(get_project_settings())
    process.crawl(*args)
    # the script will block here until the crawling is finished
    process.start() 
    # (...)
    return (result1, result2)

并开始使用类实例化调用该方法，例如：

def __call__(self):
    results1 = test.web_crawler()[1]
    results2 = test.web_crawler()[0]

并运行：

test()

我收到以下错误：

Traceback (most recent call last):
  File "test.py", line 573, in <module>
    print (test())
  File "test.py", line 530, in __call__
    artists = test.web_crawler()
  File "test.py", line 438, in web_crawler
    process.start() 
  File "/Library/Python/2.7/site-packages/scrapy/crawler.py", line 280, in start
    reactor.run(installSignalHandlers=False)  # blocking call
  File "/Library/Python/2.7/site-packages/twisted/internet/base.py", line 1194, in run
    self.startRunning(installSignalHandlers=installSignalHandlers)
  File "/Library/Python/2.7/site-packages/twisted/internet/base.py", line 1174, in startRunning
    ReactorBase.startRunning(self)
  File "/Library/Python/2.7/site-packages/twisted/internet/base.py", line 684, in startRunning
    raise error.ReactorNotRestartable()
twisted.internet.error.ReactorNotRestartable

怎么了？

回答：

你无法重新启动反应堆，但是应该可以通过分叉一个单独的过程来使其运行更多次：

import scrapy
import scrapy.crawler as crawler
from multiprocessing import Process, Queue
from twisted.internet import reactor
# your spider
class QuotesSpider(scrapy.Spider):
    name = "quotes"
    start_urls = ['http://quotes.toscrape.com/tag/humor/']
    def parse(self, response):
        for quote in response.css('div.quote'):
            print(quote.css('span.text::text').extract_first())
# the wrapper to make it run more times
def run_spider(spider):
    def f(q):
        try:
            runner = crawler.CrawlerRunner()
            deferred = runner.crawl(spider)
            deferred.addBoth(lambda _: reactor.stop())
            reactor.run()
            q.put(None)
        except Exception as e:
            q.put(e)
    q = Queue()
    p = Process(target=f, args=(q,))
    p.start()
    result = q.get()
    p.join()
    if result is not None:
        raise result

运行两次：

print('first run:')
run_spider(QuotesSpider)
print('\nsecond run:')
run_spider(QuotesSpider)

结果：

first run:
“The person, be it gentleman or lady, who has not pleasure in a good novel, must be intolerably stupid.”
“A day without sunshine is like, you know, night.”
...
second run:
“The person, be it gentleman or lady, who has not pleasure in a good novel, must be intolerably stupid.”
“A day without sunshine is like, you know, night.”
...

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