Requests CookieJar empty even thought the page have it

Question

I'm on Python 3.5.1, using requests, the relevant part of the code is as follows:

req = requests.post(self.URL, data={"username": username, "password": password}) 
self.cookies = {"MOODLEID1_": req.cookies["MOODLEID1_"], "MoodleSession": req.cookies["MoodleSession"]}

self.URL has the correct page, and the POST is working as intended, I did some print to check that, and it passed.

My output:

Traceback (most recent call last):
  File "D:/.../main.py", line 14, in <module>
    m.login('first.last', 'pa$$w0rd!')
  File "D:\...\moodle2.py", line 14, in login
    self.cookies = {"MOODLEID1_": req.cookies["MOODLEID1_"], "MoodleSession": req.cookies["MoodleSession"]}
  File "D:\...\venv\lib\site-packages\requests\cookies.py", line 287, in __getitem__
    return self._find_no_duplicates(name)
  File "D:\...\venv\lib\site-packages\requests\cookies.py", line 345, in _find_no_duplicates
    raise KeyError('name=%r, domain=%r, path=%r' % (name, domain, path))
KeyError: "name='MOODLEID1_', domain=None, path=None"

I'm trying to debug during runtime to check what req.cookies has. But what I get is surprising, at least for me. If you put a breakpoint on self.cookies = {...} and run [(c.name, c.value, c.domain) for c in req.cookies] I get an empty list, like there isn't any cookie in there.

The site does send cookies, checking with a Chrome extension, I found 2, "MOODLEID1_" and "MoodleSession", so why I'm not getting them?

Answer 1

The response doesn't appear to contain any cookies. Look for one or more Set-Cookie headers in req.headers.

Cookies stored in a browser are there because a response included a Set-Cookie header for each of those cookies. You'll have to find what response the server sets those cookies with; apparently it is not this response.

If you need to retain those cookies (once set) across requests, do use a requests.Session() object; this'll retain any cookies returned by responses and send them out again as appropriate with new requests.