How to Preload Cookies with Python3 and Selenium Chrome WebDriver

Описание: Learn how to effectively use `Selenium` with Python3 to preload cookies before making requests, streamlining your web scraping process.
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Preload Cookies with Python3 and Selenium Chrome WebDriver

When working with Selenium and the Chrome WebDriver in Python, you may find yourself facing a particular challenge: preloading cookies before a first request. This problem often arises when dealing with services that require user authentication, such as CAPTCHA systems or Web Application Firewalls (WAFs).

The main question here is: How can we add cookies for a specific domain using Selenium before actually making any GET requests? Let's dive into the solution to this problem.

Understanding the Cookie Limitation

Traditionally in Selenium, you can add cookies to the current domain using the add_cookie() method. However, if you attempt to set a cookie for a domain without first visiting it, you will encounter the error:

“You may only set cookies for the current domain.”

This limitation can be frustrating when you want to authenticate user sessions or access specific content protected by cookies.

Common Workarounds

Many workaround solutions involve visiting a different page, such as a 404 error page, to initialize the cookie domain. However, this can feel inefficient or even problematic because it triggers requests to the server, which may not always be ideal for your case.

The Key Solution: Chrome DevTools Protocol

Starting with Chrome version 64, developers gained access to the Chrome DevTools Protocol (CDP), which allows for more advanced operations, including the ability to set cookies for any domain without a preceding GET request. This is achieved through the Network.setCookie method.

Here’s how to implement this solution:

Set Up Your Environment: Make sure you have Python3, Selenium, and the Chrome WebDriver installed.

Use CDP to Set Cookies: Instead of using add_cookie, we will leverage the CDP’s capabilities.

Example Code

Here’s a Python script that demonstrates how to preload cookies using Selenium:

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

Breakdown of the Code

Imports and Options: We import the necessary libraries and set headless browser options.

Saving and Loading Cookies: Functions are defined to save cookies to a file and to load them later.

Network Commands: The script utilizes CDP commands to enable network tracking to set cookies directly for any domain.

Domain Switching: This example demonstrates fetching cookies from apple.com and using them on microsoft.com.

Conclusion

This method streamlines cookie management, allowing you to interact with domains securely and efficiently without unnecessary GET requests. By implementing the Chrome DevTools Protocol, you maximize the effectiveness of your scripts when handling session cookies across different domains.

Remember to set the selenium_cookie_file variable path to a valid writable file on your machine to ensure the code runs smoothly.

Happy coding with Python and Selenium!