This answer quotes ChatGPT
Restore me if in doubt
There are many reasons why
data may not be available. Here are some possible reasons for the problem:
1. The web server's anti-crawler mechanism, such as IP blocking, illegal request headers, etc., may cause your request to be rejected by the server or redirected to another page.
2. Network problems, such as network instability and frequent requests, may cause requests to fail or be restricted by the server.
3. The HTML code is not parsed correctly, so the required information cannot be parsed correctly.
4, the website is updated, resulting in a change in the HTML code structure or element selector, causing your crawler to parse incorrectly.
6. The website has a small amount of data, so you can't find any data when you crawl.
To determine the cause of the problem, you can try some debugging techniques:
1. Use a browser to view the original page source code and check that your crawler has extracted the required elements correctly.
2. Use the response object of the requests library to view the HTTP status code returned by the server to determine whether the request was successful.
3. Adjust the header information and try to access the website disguised as a browser.
4. Adjust the request frequency to prevent server constraints caused by frequent requests.
5. Use proxy IP addresses to prevent IP addresses from being blocked by the server.
When debugging, you can start with a small data set, check that the program is extracting the required data correctly, and gradually expand the data set, eventually determining the cause of the problem and fixing it.