Scrapy爬取无数据问题求助：无法抓取大学网站课程名称

Hey there! Let's figure out why your Scrapy spider isn't pulling any course names from that university website. The message Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min) tells us either the spider isn't even starting to crawl pages, or it's hitting roadblocks that prevent it from fetching content or extracting items. Let's walk through the most common issues to check, using your Item.py and Course_spider.py files as references.

1. Verify Your Start URL(s) Are Correct #

First, double-check the start_urls list in your Course_spider.py:

• Did you include the full URL with http:// or https://? Missing the protocol will break the request entirely.
• Is the URL pointing directly to the public course list page? If it redirects to a login screen or a dynamic portal, Scrapy won't access the content without extra setup.
• Example of a valid start URL:

  start_urls = ['https://www.your-university.edu/course-catalog']
  

2. Check Your Parse Method Setup #

If the spider isn't crawling pages, your parse method might not be properly linked:

• Did you name your parsing method parse? Scrapy uses this as the default callback for start requests unless specified otherwise.
• If you're using a custom start_requests method, make sure you're yielding Request objects with the correct callback:

  def start_requests(self):
      urls = ['https://www.your-university.edu/course-catalog']
      for url in urls:
          yield scrapy.Request(url=url, callback=self.parse)
  

3. Validate Item Extraction Logic #

Even if pages are crawled, incorrect selectors will result in 0 items. Here's how to debug:

• Use the Scrapy shell to test your selectors first. Run this in your terminal:

  scrapy shell https://www.your-university.edu/course-catalog
  

  Then test CSS/XPath selectors directly (e.g., response.css('h3.course-name::text').get()). If this returns None, your selector targets the wrong element.
• In Item.py, ensure you've defined the fields you're extracting. For example:

  import scrapy
  
  class CourseItem(scrapy.Item):
      course_name = scrapy.Field()
      course_code = scrapy.Field()
  

• In your parse method, make sure you're assigning extracted values to the item and yielding it (don't forget to loop over course elements if there are multiple courses):

  def parse(self, response):
      for course in response.css('div.course-card'):
          item = CourseItem()
          item['course_name'] = course.css('h3.course-name::text').get().strip()
          item['course_code'] = course.css('span.course-code::text').get().strip()
          yield item
  

4. Check for Anti-Scraping Measures #

Many university sites block default Scrapy requests:

• Robots.txt: Scrapy obeys robots.txt by default. If the site disallows crawlers, add this to settings.py:

  ROBOTSTXT_OBEY = False
  

• User-Agent: The default Scrapy User-Agent is easy to detect. Update it in settings.py to mimic a browser:

  USER_AGENT = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118.0.0.0 Safari/537.36'
  

• Login Requirements: If the course catalog is behind a login wall, you'll need to implement form authentication using scrapy.FormRequest to log in before crawling.

5. Check for Dynamic Content #

If the course list loads via JavaScript (e.g., infinite scroll, AJAX), Scrapy's default downloader won't render the JS. In this case, use tools like:

• Splash: A lightweight browser for rendering JS content.
• Playwright: A robust headless browser integration for Scrapy.

Once you've checked these areas, run your spider again. If you're still stuck, sharing snippets of your Item.py and Course_spider.py would help narrow down the problem further!

内容的提问来源于stack exchange，提问作者Janath Khan