Why You May Not Get All Cookie Data with the Python Requests Module

When using the excellent Requests module in Python to access web pages and APIs, you may notice that the cookie data returned in the response doesn't always contain all the cookie information you were expecting. There are a few reasons this can happen.

The Requests module stores cookies sent by the server in the response internally. You can access these cookies using the response.cookies attribute. However, servers don't always send all cookie data in every response.

Servers Omit Non-Essential Cookie Details

To improve performance and save bandwidth, servers often omit sending cookie details that have not changed or are not relevant to the client in every interaction. For example, cookie expiration dates, domains, and paths may be sent only when a cookie is first created and then omitted in subsequent responses once the client already has that metadata.

So you may find response.cookies does not contain full details on every cookie if you have an ongoing session with the server. The server assumes the client has already received the details and now only sends value updates.

Use the Session to Access Complete Cookie Details

The best way to ensure you have all cookie metadata is to leverage the Requests Session object to manage cookies across all requests:

session = requests.Session()
response = session.get('https://example.com')
print(session.cookies.get_dict())

This will print all cookies set by the server during the current session along with all received cookie attributes.

Implement a Custom Cookie Jar for Full Control

For complete control over cookie storage and access, you can also provide a custom cookie jar that saves cookies how you want:

import requests
from custom_cookie_jar import CustomCookieJar

session = requests.Session() 
session.cookies = CustomCookieJar()

response = session.get('https://example.com')
print(session.cookies) # Custom jar with all cookies

So in summary, leverage Sessions or custom jars to ensure you have full cookie details when using Requests. Omitted cookie metadata in a single response is often just an optimization, not missing information.