How to use Python to login to a webpage and retrieve cookies for later usage?

I want to download and parse webpage using python, but to access it I need a couple of cookies set. Therefore I need to login over https to the webpage first. The login moment involves sending two POST params (username, password) to /login.php. During the login request I want to retrieve the cookies from the response header and store them so I can use them in the request to download the webpage /data.php.

How would I do this in python (preferably 2.6)? If possible I only want to use builtin modules.

Here's a version using the excellent requests library:

from requests import session

payload = {
    'action': 'login',
    'username': USERNAME,
    'password': PASSWORD
}

with session() as c:
    c.post('http://example.com/login.php', data=payload)
    response = c.get('http://example.com/protected_page.php')
    print(response.headers)
    print(response.text)

import urllib, urllib2, cookielib

username = 'myuser'
password = 'mypassword'

cj = cookielib.CookieJar()
opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj))
login_data = urllib.urlencode({'username' : username, 'j_password' : password})
opener.open('http://www.example.com/login.php', login_data)
resp = opener.open('http://www.example.com/hiddenpage.php')
print resp.read()

resp.read() is the straight html of the page you want to open, and you can use opener to view any page using your session cookie.