fetch.py

import urllib
import urllib2

print urllib2.urlopen("http://localhost:8080/login", 
  urllib.urlencode({ "username": "foo", "password": "bar" }).read()

fetch_cookies.py

import cookielib
import urllib
import urllib2

opener = urllib2.build_opener(
  urllib2.HTTPCookieProcessor(cookielib.CookieJar()))
print opener.open("http://localhost:8080/login",
  urllib.urlencode({
    "user_session[email]": "foo",
    "user_session[password]": "bar" })).read()