import requests
import re

with requests.Session() as s:

    username = 'xxx@xxx.com'
    password = 'xxx'

    login_url = 'https://xxx.com`'

    r = s.get(login_url)
    html = r.text

    # Parse out the username field's name
    username_regex = re.compile('\<input value="" id="username" type="text" name="(.*)"\>')
    match = username_regex.search(html)
    username_id = match.group(1)
    print("UID: " + username_id)

    # Parse out the password field's name
    pw_regex = re.compile('\<input value="" id="password" type="password" name="(.*)"\>')
    match = pw_regex.search(html)
    pw_id = match.group(1)
    print("PWID: " + pw_id)

    # Now start an actual session where we log in
    payload = {
        username_id: username,
        pw_id: password
    }

    p = s.post(login_url, data=payload)

    # An authorised request.
    r = s.get('https://xxx.com/logged_in_page/')
    print(r.text)