How to load custom cookies in a Python request

When web scraping, it can be useful to save cookies from a previous session and load them into a new request. This allows you to resume scraping where you left off, maintaining session state and avoiding the need to reauthenticate or perform other setup steps. In this article, we'll explore how to load custom cookies into a Python request using the requests library.

Saving cookies

To save cookies for later use, we first need to extract them from an existing session. Here's an example of how to save cookies using the requests library:

from pathlib import Path

import json

import requests

# Create a session and get some cookies

session = requests.session()

session.get("https://httpbin.dev/cookies/set/mycookie/myvalue")

# Convert the cookiejar to a dictionary

cookies = requests.utils.dict_from_cookiejar(session.cookies)

# Save the cookies to a JSON file

Path("cookies.json").write_text(json.dumps(cookies))

In this code snippet, we:1. Create a new requests session

2. Make a request to retrieve some cookies

3. Use the dict_from_cookiejar utility function to convert the cookiejar to a dictionary4. Save the cookies dictionary to a JSON file named "cookies.json"

Loading cookies

Now that we have saved our cookies to a file, let's see how to load them into a new request:

from pathlib import Path

import json

import requests

# Create a new session

session = requests.session()

# Load the cookies from the JSON file

cookies = json.loads(Path("cookies.json").read_text())

# Convert the cookies dictionary to a cookiejar

cookies = requests.utils.cookiejar_from_dict(cookies)

# Update the session's cookies with the loaded cookies

session.cookies.update(cookies)

# Make a request using the loaded cookies

print(session.get("https://httpbin.dev/cookies").text)

Here's what's happening in this code:1. We create a new requests session

2. Load the cookies from the "cookies.json" file

3. Use the cookiejar_from_dict utility function to convert the cookies dictionary to a cookiejar4. Update the session's cookies with the loaded cookiejar5. Make a request using the session with the loaded cookies

By loading the saved cookies into the new session, the request will include those cookies, allowing the server to recognize the session and maintain any previously established state.

Why are cookies important for web scraping?

Cookies play a crucial role in web scraping for several reasons:

1. Session management: Cookies allow servers to identify and track user sessions. By saving and loading cookies, you can maintain session continuity across multiple requests, avoiding the need to reauthenticate or perform other setup steps.

2. Personalization: Websites often use cookies to store user preferences and settings. By including the appropriate cookies in your scraping requests, you can ensure that you receive personalized content tailored to those preferences.

3. Access control: Some websites use cookies to control access to certain pages or features. Without the required cookies, you may be denied access or redirected to login pages. By loading the necessary cookies, you can bypass these restrictions and scrape the desired content.

4. Avoiding bot detection: Websites may use cookies as part of their bot detection mechanisms. If your scraping requests don't include the expected cookies, the server may identify your requests as coming from a bot and block them. By mimicking the cookies of a real user, you can reduce the chances of being detected and blocked.

Conclusion

Loading custom cookies into a Python request is a valuable technique for web scraping. By saving cookies from a previous session and loading them into new requests, you can maintain session state, access personalized content, bypass access controls, and reduce the risk of bot detection. The requests library in Python provides convenient utility functions like dict_from_cookiejar and cookiejar_from_dict to facilitate the conversion between cookie dictionaries and cookiejar objects, making it easy to save and load cookies in your scraping scripts.