在尝试使用 python 脚本运行 Scrapy 爬虫时，遇到了问题。这个爬虫在使用 scrapy crawl single 命令时运行正常，但在 Python 脚本中运行时却无法正常运行。
问题的主要表现是 SingleBlogSpider.parse 方法从未执行，而 start_requests 方法却执行了。代码和运行脚本的输出如下：
from urlparse import urlparse
from scrapy.http import Request
from scrapy.spider import BaseSpider
from scrapy.selector import HtmlXPathSelector
from scrapy.contrib.linkextractors.sgml import SgmlLinkExtractor
class SingleBlogSpider(BaseSpider):
name = 'single'
def __init__(self, **kwargs):
super(SingleBlogSpider, self).__init__(**kwargs)
url = kwargs.get('url') or kwargs.get('domain') or 'seaofshoes.com'
if not url.startswith('http://') and not url.startswith('https://'):
url = 'http://%s/' % url
self.url = url
self.allowed_domains = [urlparse(url).hostname.lstrip('www.')]
self.link_extractor = SgmlLinkExtractor()
self.cookies_seen = set()
print 0, self.url
def start_requests(self):
print '1', self.url
return [Request(self.url, callback=self.parse)]
def parse(self, response):
print '2'
# Actual scraper code, that is never executed
if __name__ == '__main__':
from twisted.internet import reactor
from scrapy.crawler import Crawler
from scrapy.settings import Settings
from scrapy import log, signals
spider = SingleBlogSpider(domain='scrapinghub.com')
crawler = Crawler(Settings())
crawler.signals.connect(reactor.stop, signal=signals.spider_closed)
crawler.configure()
crawler.crawl(spider)
crawler.start()
log.start()
reactor.run()
Output:
0 http://scrapinghub.com/
1 http://scrapinghub.com/
2013-09-13 14:21:46-0500 [single] INFO: Closing spider (finished)
2013-09-13 14:21:46-0500 [single] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 221,
'downloader/request_count': 1,
'downloader/request_method_count/GET': 1,
'downloader/response_bytes': 9403,
'downloader/response_count': 1,
'downloader/response_status_count/200': 1,
'finish_reason': 'finished',
'finish_time': datetime.datetime(2013, 9, 13, 19, 21, 46, 563184),
'response_received_count': 1,
'scheduler/dequeued': 1,
'scheduler/dequeued/memory': 1,
'scheduler/enqueued': 1,
'scheduler/enqueued/memory': 1,
'start_time': datetime.datetime(2013, 9, 13, 19, 21, 46, 328961)}
2013-09-13 14:21:46-0500 [single] INFO: Spider closed (finished)
The program never gets to SingleBlogSpider.parse and prints '2', so it doesn't crawls anything. But as you can see on the output it does makes a request, so not sure what is going one.
Scrapy version == 0.18.2
I really cannot spot the mistake and help is really appreciated.
Thanks!
2、解决方案
答案1：
- parse() 方法实际上被执行了，只是打印没有显示出来。
- 可以将 a=b 放入 parse() 中进行测试：
def parse(self, response):
a = b
- 然后，您将看到异常。NameError: 全局名称“b”未定义。
答案2：
- 认为您所说的“无法从脚本中运行它”实际上是指“无法让爬虫生成输出文件”。这是文档示例代码中的一个错误。
- 将您的代码更改为：
if __name__ == '__main__':
from twisted.internet import reactor
from scrapy.crawler import Crawler
from scrapy import log, signals
from scrapy.utils.project import get_project_settings
spider = SingleBlogSpider(domain='scrapinghub.com')
settings = get_project_settings()
crawler = Crawler(settings)
crawler.signals.connect(reactor.stop, signal=signals.spider_closed)
crawler.configure()
crawler.crawl(spider)
crawler.start()
log.start()
reactor.run()
- 有关详细信息，请参阅此答案。