with requests.Session() as c:
    url = 'https://ps.lphs.net/public/home.html'
    USERNAME = 'My User'
    PASSWORD = 'My Pass'
    c.get(url)
    pstoken = c.cookies['pstoken']
    login_data = dict(psmiddlewaretoken=pstoken, username=USERNAME, password=PASSWORD, next='/')
    c.post(url, data=login_data, headers={'Referer': 'https://ps.lphs.net.html'})
    page = c.get('https://ps.lphs.net/guardian/teachercomments.html')
    print(page.content)