多页面爬取遇HTTP Error 404及结果异常问题求助

Hey there! Let's work through your web crawling issues one by one:

Your guess about the 404 error being caused by the 'x' URL not existing is almost certainly correct. When you send a request to a URL that doesn't exist on the target server, it will return a 404 "Not Found" status code—this is exactly what’s happening here.

To remove 'x' from ascii_lowercase, you have two straightforward options:

• String replacement: Quick and clean if you only need to exclude one character:

  from string import ascii_lowercase
  filtered_chars = ascii_lowercase.replace('x', '')
  

• List comprehension: More flexible if you ever need to exclude multiple characters later:

  from string import ascii_lowercase
  filtered_chars = [char for char in ascii_lowercase if char != 'x']
  # Convert back to a string if needed:
  filtered_chars = ''.join(filtered_chars)
  

Since you didn’t share your full code, I’ll walk through the most common reasons you might not be getting the expected results, along with actionable fixes:

• Missing request headers: Many websites block requests without a valid User-Agent (they flag them as bots). Add headers to mimic a real browser:

  headers = {
      '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'
  }
  # Use this in your request:
  response = requests.get(url, headers=headers)
  

• Incorrect URL structure: Double-check that your URL pattern matches the one used in the video. For example, if the video used https://example.com/letters/{char}, make sure you aren’t accidentally using https://example.com/{char} instead.
• Outdated page selectors: Websites often update their HTML structure. If you’re using BeautifulSoup or another parser, inspect the target page’s source code (right-click > "View Page Source") to confirm your find()/find_all() selectors are still valid.
• Unchecked response content: Print response.text to see what the server is actually sending back. Sometimes you’ll get an anti-scraping page, redirect, or error page instead of the content you expect.
• Lack of error handling: Wrap your requests in a try-except block to catch issues early and debug them:

  from string import ascii_lowercase
  import requests
  from bs4 import BeautifulSoup
  
  headers = {'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'}
  filtered_chars = ascii_lowercase.replace('x', '')
  
  for char in filtered_chars:
      url = f"https://your-target-site.com/{char}"
      try:
          response = requests.get(url, headers=headers)
          response.raise_for_status()  # Triggers an error for 4xx/5xx status codes
          
          # Parse and extract content here
          soup = BeautifulSoup(response.text, 'html.parser')
          target_content = soup.find('div', class_='your-target-class')
          
          if target_content:
              print(target_content.text.strip())
          else:
              print(f"No content found for {char}")
      except requests.exceptions.HTTPError as e:
          print(f"Failed to access {url}: {e}")
      except Exception as e:
          print(f"Unexpected error with {url}: {str(e)}")
  

If you share a snippet of your actual code (redact any sensitive URLs), I can give you even more targeted advice!

内容的提问来源于stack exchange，提问作者user5553011