Скачать или смотреть Understanding Why r.history Returns an Empty List in Python Requests

Discover how to handle redirections in Python’s `requests` library and fix the `r.history` returning an empty list issue.
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Why Does r.history Return an Empty List in Python Requests?

If you're working with the requests library in Python and you've encountered a situation where r.history returns an empty list, you're not alone! It can be a confusing aspect of handling HTTP requests, especially when working with redirection. In this guide, we'll go through the underlying cause of this issue and how you can properly set up your server and requests to retrieve redirection history correctly.

The Problem

In your original code, you were using the following Python snippet to send a request and print out the URL and history of the request:

[[See Video to Reveal this Text or Code Snippet]]

However, when you ran this code, you observed that r.history resulted in an empty list. The reason is quite simple: the original URL you are requesting doesn't actually cause any redirection. To fix this, you need to return an actual redirect response from your server.

The Solution

Creating a Redirecting Server with Flask

To ensure that your request results in a redirection, let's modify your Flask server (webserver.py) to use a redirect response instead of a plain return. Here’s how to achieve that:

Updated webserver.py

[[See Video to Reveal this Text or Code Snippet]]

In the code above, we have defined a new route that redirects clients to https://python.org. The use of redirect ensures that any request to the root URL will lead to a redirection.

Adjusting the Request Code

Next, you need to adjust your request code (main.py) to accept redirections and print both the current URL and the history:

Updated main.py

[[See Video to Reveal this Text or Code Snippet]]

Putting It All Together

Start your Flask server using the updated webserver.py.

Run your request code using main.py.

After running the above codes, you should see the final URL printed out along with the historical redirection information in r.history. Each redirect will be listed, detailing the steps taken during the request.

Conclusion

Understanding how redirections work in the requests library is crucial, especially when dealing with web traffic and API interactions. By ensuring that your Flask server utilizes proper redirection responses and that your request code is set to follow these redirects, you can successfully retrieve a non-empty history of your HTTP requests.

Feel free to play around with different URLs and redirection settings to further your understanding of how requests handles HTTP traffic!